chemistryyr12

8/3/2019 chemistryyr12

1/38

Welcome to year 12 Chemistry.

How do you pass chemistry? Lets face it this is the question you all want to know. The best way iscontinuous study. By studying consistently throughout the year you avoid the last minute cram andremember much more information. I believe that understanding chemistry involves rememberingeverything is related. By finding the links between various ideas new concepts will become easier to

grasp and it will further consolidate old theories.

I think chemistry is important because it is so closely related to human life. Chemistry is used dailyto make simple materials we find in our lives including plastics, synthetic fibres and metal alloys.This forgets the new exciting materials such as solar panels and fuel cells. Chemistry is also solvingour biggest problems like the energy crisis and global warming.

I got into chemistry for the sole reason it made the most sense. Chemistry is not a complex scienceit only asks that the scientist has common sense. You don't need to memorise scores of facts or beable to manipulate large equations, all that is needed is to ask what is the most logical answer. Somuch about nature can be understood by making only a few simple observations in the world ofchemistry.

VCE Units

Before we start let me give you a rough break down of the unitsUnit 1Unit one focuses on a part of chemistry known as chemical analysis. As chemists we need to be ableto break down chemicals we find in nature. This involves knowing how much or how manymolecules are in a solid or a liquid. This of course means we will be meeting our good old friendthe mole. BUT WAIT that's not all because we also spend a lot of time looking at the way we find

out these chemicals and the equipment we use.

Unit 2After our adventure into analytical chemistry we enter the world of organic chemistry which meansthe word of the day is Carbon. This beautiful element1 has the ability to bond to 4 other atomsallowing to make long chains and exotic molecules and interesting reactions which you will look at.Organic chemistry goes further than this however as we look at how the body uses chemistry tostore energy (carbohydrates, protein, fats) and information (DNA). Finally we find how our organicmolecules can act as medicines to help the human body.

Unit 3

Leaving the world of life sciences we enter the harsh world of industrial chemistry AKA the moneymaking chemistry. The aim here is to look at how chemical reactions workin real time. Thisinvolves looking at how fast or slow a reaction goes. We then see how complete a reaction goes andthen how these principles interact. We finish here by looking at industrial chemicals includingammonia, nitric acid, sulfuric acid and ethene and how they manage rate and yield problems.

Unit 4The last unit looks at energy. How do we get energy out of molecules and how do we use thatenergy. Furthermore how does society get that energy, fossil fuels are one way but are there otherways We then move to REDOX and look at how batteries store energy but also the other side ofredox where we flip the terminals and make electrolytic cells allowing us to control the chemistry.

1 I am a chemist I am allowed to call elements beautiful


2/38

Tutorial 1 Molecules, Mass and a little bit of Mixtures

The basics

So lets start with clearing up some basic ideas.Chemical Really bad term actually usually synonymous with solution but not always. We dont

use it

Atom - An atom is a neutral species made up of electrons surrounding an inner nucleusmade up of protons and neutrons

Molecule - A molecules is made up of two or more atoms bonded in some way together

1) So what is an ion?

The mole

Atoms are are very small. In order to make the numbers we use much easier when doingcalculations we need a new way of counting atoms. So we introduce the mole.

The mole is just an amount of something, it has the unit mol but if you get confused just think of themol as being the same as dozen. A dozen is just an ammount of something like a dozen rolls or adozen eggs but if you asked someone for a mol of eggs you would end up with

6.02 x 1023

This is a HUGE NUMBER!!! 6.02 x 1023 = 602,000,000,000,000,000,000,000.

A mole of marshmellows would actually cover the earth 19km deep. For perspective thats twice the height ofmt everest..2

1 mole is defined as Avogadros Number: NA

= 6.02 x 1023 mol-1 and the symbol for mol is n. We can use

this number to convert between number of molecules and amount in mole.

2) how many molecules are in 2 moles of H2 ?

3) how many atoms are in 2.5 moles of N2 ?

4) If i have 700 million (7*108) jars of nutella how many moles of nutella jars do I have?

Now you can see the importance in the distinction between atoms and molecules.

So why pick such a large number well 1 mole of carbon atoms actually has a weight of 12 grams.This brings us into atomic and molecular mass.

2 Actually its 19.31km. My favourite is there are more molecules of water in a glass of water than there are glasses ofwater in all the oceans


3/38


4/38

Percentage mass is another place where these formulas arise and these are usually more complexthan the above questions. These types of questions involve you needing to write an equation and usemoles to work out how much mass of a specific chemical there is?

7) 2 grams of a common sulphate fertiliser was dissolved in excess water. It was then allowed toreact with Barium(II) Chloride to produce 5.2 grams of precipitate.a- write down the chemical formula of this reaction

b- how many mole of precipitate is formed?

c- how many mole of sulfur is there?

d- what mass is the above sulfur?

e- what is the percentage mass of sulfur?

f-what is the percentage mass of sulphate?

Similar questions can be broken down in this way also. This method of analysing chemicalcomposition using mass measurements is known as gravimetric analysis. Gravimetric analysis is thefirst of these methods for analysis.

Barium sulphate is actually insoluble in water. This makes it useful for this method. There are othersalts that are also insoluble in water including silver chloride (AgCl) and lead sulphate (PbSO 4)knowing which salts are soluble and which are not will be something you will study during the year.

Volumetric analysis

So now lets look at volumetric analysis. Quite similar to gravimetric except we use ourconcentration equations being

n=cvc1v1=c2v2

where C is concentration and it is measured in molar (M) and is (mol/L). volume is of coursemeasured in litres.


5/38

8) If I have 150mL of 0.4 M sulphuric acid how much water needs to be added to reach aconcentration of 0.12 M?

9) What would the concentration if 5 grams potassium hydroxide (KOH) was dissolved in 250mLof water?

Lets now look at actual volumetric analysis. This usually involves titration, this is the process wheresmall amounts of molecules usually3either an acid or base are steadily added until all the reactant

base or acid has been neutralised. The amount required to react can be used to know theconcentration.

An analogy I prefer is having a drink you don't know how much costs. You pay one cent at a timeuntil the bar tender finally says you have paid enough and so you know the price of the unknowndrink. In this case the money represents acid and the unknown price is the amount of base.

When the concentration of acid and base are the same the point is known as the equivalence point.To find this equivalence point we use an indicator, when the indicator changes we say this is theend point. To have a titration system work the end point of the indicator must lie near the pH of theequivalence point.

There are some other definitions in volumetric analysis that need to be knownAliquot: the volume delivered by a pipette. (i.e. the thing to be analysed)

Titre: the volume delivered by the burette (i.e. the thing you are using to analyse the other thing).

Standard solutions: solutions of known concentration.

Primary standards4: solution of compounds with properties that allows it to be used accurately intitrations. These properties include:

High purity

Be of known formula

Must not absorb moisture or carbon dioxide from air.

Be soluble

Have a large relative formula mass (to minimize error in weighing with a scale).

Inexpensive.

Concordant Results: three titre volumes within 0.05mL of each other.

Indicator: a substance that indicates that the reaction has reached end point by changing colour.The indicator must be appropriately selected to match the pH of the reaction. (e.g.phenolphthaleinchanges colour between pH 9 & 10; methyl orange changes colour between pH 3 & 4).

3 Redox reactions can also be used in titration reactions4 There are such things as secondary standards that dont have the properties listed


6/38

(cover bellow as homework or if time at the end of class)

BACK TITRATIONSinvolve adding an excess of one reactant that is added to the solution to beanalysed, then the excess titrated against a standard. This is done when the original reaction is hardto accurately determine, for example where the rate of the reaction is too slow.

10) A commercial concrete cleaner contains concentrated hydrochloric acid. A 25.00 Ml volume of

cleaner was diluted to 250mL in a volumetric flask. A 20.00 mL aliquot of 0.4480 sodium carbonatesolution was placed in a flask with an indicator. A titre of 19.84mL of hydrochloric acid was neededto reach the end point. Calculate the original concentration of acid in the floor cleaner.

Do you have a mole problem? If so call Avogadro at 6022-1410

Advertisement


7/38

Tutorial 2 What really is in my drink? Chemical analysis

With chemical analysis there are two main methods qualitative and quantitative analysis.

Qualitative analysis This is actually the situation where the identity of the chemical/molecule isnot known. Qualitative analytical techniques are used to identify unknown

chemical.

Quantitative analysis- This is where the amount of substance is unknown. Quantitative techniquesare used to find out the concentration of an unknown molecule.

Analytical techniques can be one or the other or both. There are two main analytical techniqueschromatography and spectroscopy.

Chromatography- This operates by separating molecules out. This is done by having twophases a mobile phase and a stationary phase. Some molecules prefer to bein the stationary phase and whilst some molecules are in mobile phase. The

mobile phase moves so the chemicals get separated.

Spectroscopy- This uses light to identify specific molecules or constituent parts of amolecule. The light absorbed by molecules can be used as a fingerprint toidentify specific chemicals or bonds.

ChromatographyThere are many methods of chromatography so we shall start with the simplest and then increase incomplexity

Paper and Think layer chromatography (TLC)This is one type of chromatography that you may be familiar with. A strip of filter paper or a TLC

plate which is coated in TiO2 is placed in a solvent be it water for paper or hexane or ethanol forTLC plate. As time continues the different species dissolved in the solvent travel up the paper orTLC plate. Some travel faster because they prefer to be dissolved in the solvent whilst others travelslower.

On the left is a model of a TLC plate. The right species has movedfurther than the left species meaning it is prefers to be in thesolvent. We now must introduce retention value. It follows theequation

R=(distance species traveled)(distance solvent travls)

1) what is the mobile phase and what is the solid phase for a TLCplate

2) what is the retention value for the left and right species?

3)why can retention values never be greater than 1?


8/38

Column and high pressure liquid chromatography (HPLC)Moving now to column chromatography5. This involves a solution being passed down a column of

beads coated with TiO2 or other substances. The advantage of this over TLC is that the end productsto exit the column can be tested in spectroscopy techniques or else the separated species can be usedin other reactions. It also a much faster more accurate technique.

HPLC works the same as column chromatography except apump is used to force the fluid through the column veryquickly. Both techniques need a detector at the bottom of thecolumn to separate the different species exiting. The solvent issometimes known as the eluent whilst the exiting species issometimes known as the eluate.

Unlike in TLC column chromatography involves usingretention times. This means the time taken for the species to

pass through the column over the time taken for the whole

solvent to leave the column.4) what would this equation look like?

5) what is the mobile phase and what is the stationary phase?

Gas liquid chromatography (GLC)For volatile chemicals, small molecules or gasses it is best to use GLC. GLC operates by heating upa sample until it becomes a vapour. It is then pushed along a substrate lined column by a carrier gas

which is an inert gas usually nitrogen or helium. The species that is the smallest or most adheres tothe carrier gas is the first to exit the column.

As with HPLC a detector is required at the end of the columnand it measures the time the species exit. This of course meansthat retention time is the value used.6

6) draw the main features of a GLC including column andvaporisation chamber

7) What is the mobile phase and what is the stationary phase?

SpectroscopyThe 'detector' mention above is usually a spectrometer and is used to separate the the differentmolecules identity thus allowing for a complete understating of all the constituents of a mixture

Before we go into spectroscopy I want to talk about monochromators. These are used in a widerange of spectrometers. They work in the same way as a glass prism they split white light into aspectrum. This allows for individual colours of light to be used or shined onto the chemical sample.By separating the colour spectrum we can get a spectrum of what colours are absorbed more

5 Imagine a line of kids going down a water slide. Some kids will be really excited and love the water and go downquickly. Others will be scared and grab onto the side preferring the safe solid phase and go down slowly. You canuse this to separate the brave kids from the scared kids.

6 What emotional disorder does a gas chromatograph suffer from? Separation anxiety


9/38

than others. The principle of spectroscopy. Also different colours of light are refereed to as havingdifferent frequencies or wavelengths because light is a wave.

Atomic absorption and emission spectroscopyThese types of spectroscopy use the ability for atoms to absorb specific frequencies of visible light.These types of spectroscopy are useful in areas where metals are used or salts as metals have verydefined absorption. The electrons in an element get excited by light and move further away from the

nucleus

Atomic emission spectroscopy is actually a sophisticated form of the flame test. In the flame test weheat up a sample and see what colour comes out. In an emission spectrometer the same occurs but aslit is used to make sure the light is coherent and a monochromator separates the spectrum.

8)label the above diagram for emission spectroscopy.

So atomic absorption tests the absorption of light and it was developed by an Australian (we rock).It operates by turning the sample into a vapour using a flame. If atoms have very precise emissionwavelengths ie very precise colours they produce then the light that an atom will absorb will bevery precise also.

After shining the light onto the vapour the light will be absorbed. The spectrum is then split with amonochromator and the amount of light reaching the detector is subtracted from the amount of lightshone on the sample to get the amount of light absorbed. AAS gives more information than AES.

9) label the diagram above for Absorption spectroscopy

10) One of the above produces a spectrum with bright lines on a dark background the otherproduces dark lines on a rainbow spectrum. Which belongs with which and why?


10/38

UV Vis Spctroscopy and calorimetry7So whilst metals absorb and emit visible light organic molecules absorb UV light as well as a littlevisible light. Unlike above the electrons don't get moved from the nucleus they usually are justmoved around the molecule and this process doesnt involve making the solution into a vapour.

11) label the diagram above for UV vis spectroscopy.

UV Vis spectroscopy operates by shining specific frequencies(colours) of light on a sample and

seeing how much is absorbed. UV Vis spectroscopy can be used as qualitative and quantitative asthe amount of absorption says how concentrated the solution is and the light it absorbs says whattype of chemical is present.

This part is important. If a solution is blue what colour light does it absorb? If you answered blueyou are wrong. A blue sample will absorb all light except one, blue! That is the colour it reflects. Itsnot perfect of course so something that looks blue usually means it absorbs a lot of itscomplementary colour red.8

Calorimetry only involves using one colour of light and measuring how much is absorbed. This

makes it a quick but purely quantitative process.

Some UV Vis spectrometers are made more complex by adding a beam splitter to scan a referencecell. A cell to know how much the zero line absorbs.

Infra red spectroscopyInfra red is lower energy light than UV or visible light and unlike moving electrons it actuallyvibrates bonds. IR light happens to be a wavelength that can be absorbed by chemical bonds.Chemical bonds vibrate, imagine the bond that links oxygen to hydrogen in water as more like aspring. By hitting the spring with the right wavelength it can absorb it and start to bounce. Thismeans that IR spectroscopy can be used to find out what bonds are present in a molecule.

I would put another diagram but it would look identical to the UV vis spectrum diagram except thelight source would be an IR source. So instead here are some absorbances of specific functionalgroups. IR light is simply heat, so an IR source is usually a very hot lamp. IR spectroscopy is goodat determining the parts that make up an unknown compound.

7 This is my favourite because I use it all the time8 This is not why the sky is blue. Some things have colour because they emit a specific colour or they scatter more of

that colour.


11/38

Bond Location Wavenumber (cm-1)

C-Cl Chloroalkanes 600-800

C-C Alkanes 750-1100

C-O Alkanol esthers 1000-1300

C=O Carboxylic acids and esthers 1680-1750C=C alkenes 1600-1700

O-H Carboxylic acidsAlkanols

2500-33003200-3600

C-H AlkanesAlkenes

2850-31003000-3100

N-H Amines (primary) 3100-3500

12) where would you expect ethanol absorbance peaks to be?

NMR spectroscopyThis is the last spectroscopy technique. Nuclear magnetic resonance is dependent on somethingknown as nuclear spin. When a charge spins it creates a magnetic dipole in the case of an proton orneutron these magnetic dipoles are like small magnets on an atom. In cases when there are evennumbers of protons and neutrons the magnets can balance but in other cases there is a magneticdipole. In a material these dipoles point in random directions and so have no effect however when amagnetic field is applied a different set-up occurs.

Magnets naturally line up to external fields so atoms that have a magnetic spin can align to the fieldfor lower energy level. There exists however a higher energy level which occurs when the atom

switches to point against the external field. To do this the atom must absorb energy in the form oflight but this light is in the form of radio waves. By doing this we can get an accurate map on the

position of all the atoms in a molecule because the energy required is also dependent on what isbonded to the atom.

So what do you need? You need a large magnet to set up the field, you need a radio wave source toexcite the atoms. NMR can be used for hydrogen and carbon, it can be used with other atoms buthydrogen and carbon are the most used. You may be aware of an MRI that takes accurate pictures ofthe body, this machine works in the same way.


12/38

What has been presented is a rough guide of all the techniques (except mass spectrometery becausethere is not enough time but if there is in class your tutor can go though it)

remember this is a basic introduction and there is more understanding required for all the techniquesespecially on how to read a spectrum. Finally the other important factor is it is not one single

technique that is used to identify species in a material but a combination of a lot of these techniques.

13) A sample of rust if found on a metal surface which technique would be used to identify it andwhy?

14) the amount of chlorophyll in a sample is to be studied what colour light would be used in a UVVis spectrometer?

15) Which of the following would be an example of a quantitative analysis?

The identification of metal cations using a flame test

The separation of dyes from a felt tip pen using paper chromatography

The identification of amino acids using electrophoresis.

The determination of the mass of sodium hyrdroxide in drain cleaner by volumetricanalysis.

16) Which one of the following processes would involve qualitative analysis?

The determination of the presence of calcium ions in water.

The separation of the colours in ink by paper chromatography.

The identification of a drug by HPLC.

The determination of the percentage of alcohol in boll by GLC.


13/38

Tutorial 3 - Plastic fantasticAREA OF STUDY 2 is called organic chemical pathways. This is an introduction to one of thelargest and broadest areas in the chemical world, Organic Chemistry. Areas under this heading canrange from synthesis of (making) new life-saving drugs for the pharmaceutical companies to

production of fuels and plastics from oil.

In this context organic means something very different from organic food. Organic meanschemistry using molecules made mostly of Carbon, Hydrogen, Oxygen and Nitrogen. For most ofthis course, we will be looking at molecules made of carbon and hydrogen withfunctional groupsattached. These chemicals are sometimes known as hydrocarbons given the presence of hydrogenand carbon.

In this topic you will learn how to name and draw organic molecules. The groups of organicmolecules tell you something about the arrangement of the carbon backbone of the molecules.

Alkanes and Alkenes

Most organic molecules in this course are alkanes oralkenes. Alkanes have no double bonds whereAlkenes have 1 double bond. The name of the molecules are based primarily on the number ofcarbons in the longest chain.

Number ofcarbons

prefix

1 Meth-

2 Eth-

3 Prop-

4 But-

5 Pent-

6 Hex-

7 Sept-

8 Oct-

9 Non-

10 Dec-

2) Is the substance C4H6 an alkane or an alkene?

Deducing the name of a hydrocarbon from its chemical formula is quite easy. Simply by countingthe number of carbons gives you the prefix and the formula says whether you add -ane or -ene tothe end.

3) What is the name of of the substance in question 2?

Drawing alkanesThe easiest way to draw alkanes is follow a step wise process.

1. Find out how many carbons are in the chain and draw a row of that many carbons connected

The first step in understanding organic chemistry is toremember that carbon can bond to at most 4 other atoms.

1) why can carbon bond to 4 other atoms?

It is this process that makes organic chemistry so rich. Ifcarbons can bond to a maximum number of atoms this allowsus to create formulas to know whether a species is an alkane,an alkene or something more. These formulas are:

Where n can represent any number. Molecules with one oremore double bonds are refereed to as unsaturated and nodouble bond is known as saturated.

alkane CnH(n+2)

alkene CnHn


14/38

2. Draw bonds off each carbon so that they have 4 bonds each.

3. Places where the bond terminates at nothing add a hydrogen atom

4) draw propane in full form

The phrase 'full form' was used because there are several ways to draw organic molecules. Full formshows all the bonds. Semi structural does not show the bonds to Hydrogen and skeletal does notshow hydrogen at all and the points become carbons and everything is inferred. The last is preferredin large systems. The three types are shown left to right bellow for ethane.

Unfortunately the world is not that simple because there are such things as branched alkanes.Carbons can bond to 4 other atoms but it can bond to other carbon atoms the simplest example is 2 -methylpropane

As can be seen the central carbon is connected to 3 carbons. Thesemolecules need to be named in a specific way to ensure they arecopied correctly

1. Find the longest continual chain of carbons. Here it is 3 andbecause it is symmetric you can pick whichever you want. Iusually circle the chain once I have done this.

2. Circle the substituents. These are the extra bits, the extra carbonon the middle carbon

3. Number the chain from the end closest to the first substiuent. Again symmetrical.

4. Name the substituents by placing the location it is bonded to followed by a dash then thenumber of carbons. In this case it is off carbon 2 so we write 2 and its only one carbonwhich is meth and we add yl to the end finishing with 2-methyl.

5. Name the substiuents in alphabetical order. Only one no need here

6. if there are two methyl groups for example you number the carbons like 2,3 or 2,2 and

write dimethyl. Tri for three of the same.7. Add the prefix to the name of the longest chain if it were just an alkane. In this case 2-

methyl and its 3 carbons in the longest chain so. 2-methylpropane

It is a long process but it is also an important one

5) what are the names of these branched alkanes

C C

H

H

H H

H

H

CH3 CH3

C

C

C

C

HH

H

H

H

HH

H

H

H

CH2 CH CH CH3

CH3

CH3

CH3 CH2 CH CH CH2 CH3

CH2

CH3

CH3CH3


15/38

6) Draw the molecule 2,3-dimethylbutane

Before we move on it is worth saying that alkenes are named in the same way. The only differencewith an alkene is the numbering goes from the end closest to the double bond and a number must be

put in order to identify where the double bond is. The suffix is also -ene

7)Name the molecule on the left and draw 2,2 dimethylhex-3-ene on the right

IsomersIsomers are molecules that have the same molecular formula (so they contain the same atoms) buthave a different structural formula (the atoms are arranged in a different way). So take our exampleabove with 2-methylpropane by counting the carbons there are 4 and the hydrogens there are 10 so

the molecular formula is C4H10 which is the same molecular formula of butane. These are hence

both isomers and why 2-methylpropane is sometimes refereed to as isobutane.

My suggestion for finding all the isomers of a molecule is to steadily remove carbons from theterminals and add them to knew places on the back bone until all the combinations have been done.Be aware however that molecules can be moved around and rotated so dont repeat the sameconformation

8) draw all the strucural isomers of pentane (hint there are only 3)

Functional GroupsCarbon and hydrogen are not the only tricks that organic chemistry has there are also a wide rangeof other groups that can be bonded. These groups are refereed to as substitutions and can haveoxygen, nitrogen and many other elements. It is functional groups that give organic molecules theirreactive chemistry.

CH2

CH

CH2

CH3


16/38

Formula Name Suffix Example

-Cl, -Br, -I Halogen alkanes

sometimes known ashaloalkanes

Chloro-, Bromo, Iodo-(prefixes)

C C Cl

H

H

H

H

H

chloroethane

-OH Alkanols/Alcohol

sometimes known ashydroxyl

-ol

C C OH

H

H

H

H

H

ethanol

C

O

OH

Carboxylic acid -oic acid

C C

H

H

H

H

H

C

O

OH

propanoic acid

C

O

O

Ester -yl (suffix for alkanol)-oate (suffix for acid)

C

O

O

CH3CH2

CH3

Ethyl ethonate

NH3 amine Amino- or -amineCH3

CH2

NH2

aminoethane

So how do you name the molecules. Same as you did above except circle the substitutes and add theprefix and their location. Always find the longest chain and place that first then work out if it is analkane or an alkene or something else to finish the suffix. Place the prefixes before that.

9)Name and draw the molecules bellow

Chemical reactions with hydrocarbonsThere are several reactions that can occur with hydrocarbons including substitution and esterformation. The one being analysed today is the addition reaction. Addition reactions are when bonds

2-amino-3-bromobutan-1-ol

Cl

CH3

CH

CH

CH2

CH3CH3


17/38

(generally double bonds) are broken in order to form new bonds to new atoms that will be added tothe molecule. Alkenes undergo addition reactions as they have a reactive C=C double bond that can

be broken in order to add something.

Ethene is the normal starting material because it is small so can be used to produce a wide varietyof more complex materials. Ethene is sourced from either natural gas (using fractional distillation,followed by steam cracking and more distillation) or crude oil (by-product of catalytic cracking to

produce small fractions).

When you react the right molecule with ethane it adds across the double bond. This turns the base moleculefrom an alkene into an alkane.

H2C=CH2(ethene)+Br2HBrCCHBr(1,2dibromoethane )10) draw this chemical reaction

As Br2 is a dark brown colour in aqueous conditions, but dibromoethane is colourless, this formsbasis for a simple test for alkenes alkenes can decolourise bromine water. So what else can beadded to ethene other than halogens.

11) complete these formulas

Ethene and other double bonded molecules can even undergo polymerisation. A polymer is longchain of molecular repeating unit. Much like a chain is made up of links polyethene, the material in

plastic shopping bags, is made up of single molecules of ethen linked together

C C

H

H H

H

C C

H

H H

H

C C

H

H H

H

ClH

H H

OH2

+

+

+

C C

H

H H

H

C C

H

H H

H

+


18/38

Benzene RingThe ethene based polymer polystyrene contains a benzene ring. This is a six-membered ring withone hydrogen bonded to each of the carbons. Although often depicted with alternating single anddouble bonds, the ring in fact contains 6 equal bonds,. The bonds are of strength in between a singleand a double, with a de-localised pool of electrons. The double bonds oscillate and each carbon isalways has 4 bonds. Benzene rings are flat and offer a chance for molecules to conduct electricity.

In the body

As said these organic molecules are found throughout the body and bellow are a few examples of

where.

N C

C

C

O

O

H

H H

H

H

H

H

This is glucose on the left, it is known as a carbohydrate or more commonly known as a sugar. In itsbase form it can be burnt to produce energy in the body. It contains multiple alcohol bonds that

allow it to dissolve in water and bond to other glucose molecules.

To the middle we have what is known as a fat. This is another form of energy storage the body has.

These molecules can also be burnt. As can be seen there are many long carbon chains but they are

stuck to a back bone using an ester bond.

On the right we have an amino acid known as glycine. Amino acids can be strung together like

polymers to make proteins that are found throughout the body. It is proteins that ensure the corrrectoperation of cells and other mechanisms. As can be seen there is a carboxylic acid and a amine

functional group on the molecule and it is these that bond to make polymer chains.

This subject is the most complex of the first semester (dont stress if you didnt get it). There are

more reactions and a couple more functional groups but understanding the basics of organic

chemistry will make understanding biochemistry much easier and will also help in the future.


19/38

Homework

What is a common feature of all alkene molecules?

The general name for the any hydrocarbon that has the chemical formula C8H18 is;

Draw the structures for the following hydrocarbons.

Nonane

Hetp-1-ene

2-methylpentane

2,3-dimethyloctane


20/38

Tutorial 4 Fast and the FerrousSome reactions occur very slowly over the period of years (like a rusting bridge the oxidation of

Iron) and other reactions occur extremely quickly (like an explosion the oxidation oftrinitrotoluene, TNT). The speed at which the reaction occurs is called the RATE of Reaction.

Collision model

To understand reaction rates we must first create a model to base them on and in this case we usethe particle, collision model.

This model suggests that all molecules are simply hard spheres, these spheres take up no volumethey have no attractive forces and all the energy they possess are in the form of kinetic energy(movement).

In order for a reaction to progress two or more reactants must meet and this is done with a collision.When two reactant molecules collide and if they have sufficient energy(activation energy) they willreact to form a product species. The rate of a reaction is measured by the amount of successfulcollisions as these will produce more products (or reactants).

This model is simplified however it can be used to predict rates or reaction and understand themechanics of a system.

Rate of reaction

There are four main ways in which the rate of a reaction can be affected and that includes,concentration, surface area, catalyst and temperature.

ConcentrationThe fastest way to make more bubbles in a sink is to add more detergent this is the basic theory

about concentration the more reactants the faster the process occurs. This must be of courseexplained in the collision model.

As there are more reactants the amount of collisions that can occur increases. More collisionsmeans more successful collisions meaning a faster rate. Concentration however also applies tovolume and pressure. By increasing the pressure of a gas vessel the particles are pushed closertogether effectively increasing the concentration, the same happens when the volume is decreased.

Surface AreaA spoon full of sugar does more than make the medicine go down imagine I place a spoon full ofsugar and a cube of sugar in a glass of water which dissolves first? The powdered sugar dissolves

first because it has a greater surface area, but how does that effect the reaction rate.

By having an increased surface area there are more reactants with which to collide thus increasingthe amount of collisions and hence the rate. Large objects have a smaller surface area than smallerobjects imagine cutting an orange in half, in the beginning the surface area is just the skin butafterwards the surface are is the skin and the exposed halves.

Lastly most of you have heard of the mentos in the coke experiment. I bet a fair few of you think its

some kind of reaction, well its not really. Coke like all soft drinks has a lot of dissolved CO2 so

to form bubbles they need a rough surface to form on. By shaking a bottle you force all the gas tofind a rough surface on the inside of a bottle. Mentos looks fairly smooths but in reality there are

many small dimples on the surface giving it a massive surface area, all of which are places thatbubbles can form and hence why a lot of bubbles form at once and it appears to explode.


21/38

CatalystCatalysts are not readily encountered in everyday life, the only place that one might find one is inthe exhaust of your car that acts to clean the gases slightly before releasing into the atmosphere. Sowhat is a catalyst?

A catalyst is a molecule or a solid that speeds up the rate of a reaction without participating in the

reaction. A catalyst ensures that the collisions between molecules is on average more successful andhence lowers the activation energy. There are two types of catalyst: hetrogenous and homogenous.Homogenous means they are chemicals that do react but return to their original state before thereaction is complete. Hetrogenous means they are a surface for which reactant molecules can easilymeet and react.

A catalyst is a little like a dating website, it doesn't intervene in your love life but it gives you agreater chance of successful relationships.

TemperatureThis is one of the most effective ways of increasing the rate of reaction and we all know that things

burn faster when they are hot and sugar dissolves faster in hot water, but why.

To understand why we first must ask what temperature is. Temperature is a measure of the kineticenergy of molecules or in other words how fast the reactants are moving. To increase a reaction rateis of course to increase the speed the molecules are travelling and this is done with heat andincreased temperature. With the particles moving faster the amount of collisions increases, you aremore likely to bump into someone if everyone is running than if you are all casually walking. Morecollisions means more successful collisions which means a faster rate.

The other way temperature can affect is to remember thatthe energy or speed a reactant hits another reactant is whatguarantees whether a reaction progresses or not. To theright is a pictorial representation of this idea. On the verticalaxis is the number of molecules and the horizontal axis isthe energy of the reactants. There are a lot of reactants withlow energy but not many with high energy. As you go fromT1 to T2 we can see there are more molecules with highenergy. There is also a point called Ea which is the energy toactivate the reaction. At the higher temperature there aremore molecules with higher energy than Ea so more molecules that can react.

Temperature has one of the greatest effects on rate and by raising the temperature you can speed upthe reaction

1) Why do people rub batteries with their hands when they are going flat?

2) Why is it unwise to put a whole log on a fire instead of smaller twigs?

3) A catalyst is added to a chemical reaction. Will this increase the amount of product from thereaction?


22/38

Here is a good analogy. Imagine a year 7 dance set up by the school and lets pretend that asuccessful reaction is getting two people dancing together, how might you increase the chance of

people getting together? You could get more guys and more girls or put them in a smaller room sothey are forced to talk to one another (concentration). Guys and girls tend to form social circles soyou could break them up to make it easier for people to approach one another without beingnervous (surface area). You could put some good music on that gives people a reason to

dance(catalyst). Or you could give people alcohol making them move around and dancemore(temperature more movement) and giving people more confidence to talk to strangers(temperature lower Ea).

Though giving year 7 kids alcohol may not be looked at unfavourably from the education board.

Enthalpy

Enthalpy is a measure of what the energy change for a reaction will be. It can tell you how muchenergy you need to put into a reaction or how much energy is given out by a reaction. Enthalpy isgiven the symbol H. All the products and all the reactants have their own enthalpies . You can thinkof molecules as bags of energy if there is more energy in the bags at the start than there is at the

end of the reaction then energy has been lost. If there is more at the end than there was at the startthen energy has been gained. H Is used to describe a change in enthalpy

The Enthalpy can be calculated by:

If energy is gained then H will be POSITIVE (>0) this is called an endothermic reaction. If energy is lost then H will be NEGATIVE (


23/38

known as a dynamic equilibrium. This is in English known as an oxymoron because dynamic meansmoving and changing whilst equilibria means unchanging.

H2g+I2g2HI2gThis is a well used equilibria of the formation of hydrogen iodide. Equilibria in this context means

that the concentration of H2 , I2 and HI are the same. This means if you were able to count

how many H2 molecules there were and then wait 5 minutes if it were at equilibria the numberwould be the same.

The reason that it is dynamic is because although there are the same number the system continues to

react but at a specific rate. For every molecule of H2 that is reacted and disappears two

molecules of HI decay to produce one molecule of H2 . I like to think of it as people on a

ferris wheel, there will always be only 12 people on the ride at one time but people continually geton and get off.

With this idea that chemical reactions can go forwards and backwards we are left with the idea that

equilibria reaction never go to completion. This is true but it does bring the question how farforward can a reaction go. Some reactions proceed far forward whilst others do not. We call this theposition of equilibria.

When we put reactants like H2 and I2 in a reaction vessel they take a while to react before

the reach equilibria. When they do however reach equilibria there are several things we can do tothe reaction to shift the equilibria position and they all rely on an idea called le chatlier's principle.

4) write down Le Chatelier's principle in your own words

Using Le Chatelier's we can affect equilibria in some interesting ways.

Affecting concentrationby increasing the concentration of a reactant the system will attempt to decrease the concentrationof that reactant by making more product until the system reaches equilibrium again. The connectioncan be changed also by removing reactants or products as well.

HClaq+H2OlCl1

aq+H3O+1

aq

5) For the above dissociation of hydrochloric acid what would be the effect of removing water viaevaporation?

Le Chatelier's principle also allows us to explain why some reactions go to completion take thereaction bellow

AgNO3aq+NaClaqNaNO3aq+AgCls

As the reaction proceeds forward silver chloride falls out of solution9 and because solid is adifferent phase to the aqueous the system will seek to increase the concentration of AgCl by pushing

9 Remember if you are not part of the solution you are part of the precipitate


24/38

the reaction forward hence the same effect will occur again.

Pressure and VolumeBy changing the pressure or volume of a system the system will attempt to revert back to its originalstate. By increasing the pressure the system will attempt to decrease the pressure and to that it willmove to the reaction in the direction ofleast molecules.10 If the volume is increased the system will

attempt to increase the volume so make more particles. Also pressure and volume are inverselyproportional, by increasing pressure you decrease volume. Lastly by increasing the volume this

effect can be thought of as decreasing the concentration of all products. n=c

v

N2g+3H2g2NH3g

6) what would the effect of increasing the pressure have on the above reaction, the production ofammonia. (immediately and after time)

7) what would the effect be if the reaction vessel had a sudden increase in volume?

8) The pressure of the above reaction is doubled what would be the result of this change?

Lastly on the topic of pressure and volume what would be the effect of adding an non-reactive gaslike Helium to any of the above reactions. Some people might say it would increase the pressureHOWEVER this is false a noble gas will actually not affect the concentration of a gas as the moleand the volume are same. Adding helium will have no effect.

TemperatureThese are the most interesting effects. Firstly the above alterations on equilibrium don't change theequilibrium constant which is the ratio. Lets for example suppose a reaction

AgBg

A could be water in liquid form and B could be water vapour, or anything else. Lets say you have50% of each and you increase the concentration of A to 60%. The system will decrease A until theratio returns to 50%. This return to equilibria is a manifestation of Le Chatlier's principle. This ideais important because temperature effects don't work this way in fact change the equilibriaratio/constant.

So how does temperature affect a reaction? Imagine burning methane an exothermic reaction thatreleases heat. What would be the effect on applying heat to this reaction? The system would oppose

the change by cooling the reaction which can only be done by moving the equilibria to the

10 If both the reactant and product side had the same amount of reactants then the system would not be affected bypressure and volume changes.


25/38

backward reaction and stop burning the methane.

Take the melting of ice, this is an endothermic reaction because the ice absorbs energy to break thebonds in its crystal lattice. If you apply heat to the ice the system will seek to reduce the amount ofheat, It will do this by proceeding forward and moving the equilibria in that direction.

NaOHs+ H

2O

Na+

aq+OH

aq H=44.51KJ /mol

9)Should this reaction be cooled or heated to maximise the yield of ?

This above principle actually has an essential consequence on industrial chemistry that is exploredin the next tutorial.


26/38

Tutorial 5 Feeling hot hot hot

The bellow reaction is one the most crucial steps in the formation of sulphuric acid

SO2g+O2gSO3g H=26KJ /mol

You can see that this reaction is an exothermic reaction.

1) By applying a large temperature to this reaction what will be the effect on the yield?

2) By applying a large temperature what will be the effect on the rate?

Here is the industrial dilemma! So on the one hand you want to make lots of sulphuric acid so youcool down the reaction so that the system will move forward. On the other hand you want to roll outthese barrels of sulphuric acid quite regularly so you want to ramp up the rate so you turn up thetemperature. Due to this you want to pick a temperature that optimises both of these processes.

This also explains why so much research goes into catalysts so that the rate of reactions can beaccelerated at low temperatures. High pressures are used to optimise yield and rate as well.

Industrial chemistry

There are 4 main industrial processes that will be studied in year 12 are: ammonia production, nitricacid production, sulphuric acid production and ethene production. Usually in school one of thesewill be studied in detail but all of them need to be learnt to some degree.

Again due to time constraints we cant go though all these reactions but with the general principlesof rate and equilibria the industrial processes become much simpler.

Energy

We have seen how energy is used in a reaction however it can be further explored. When a materialis supplied with energy the way the material stores that energy is dependent on its heat capacity.Some materials store energy well and do not have a large increase in temperature whilst others do

not store energy well and so the temperature increases rapidly.

This can be seen at the beach, the sun is supplying the sand and the water with the same amount ofenergy however the water stores the energy easier and does not heat up. The sand in contrast cannotstore the heat well and heats up a lot11. The formula to explain this occurrence is bellow.

Where 'm' is equal to mass in grams, 'T ' is a measure of the change in temperature in other

words TfTi , 'E' is a measure of energy and is measured in joules. The heat capacity 'C', is ameasure of how well a material stores that energy, the larger the number the better it is at storingthat energy without heating up. In the table are some common heat capacities.

11 Usually resulting in really hot feet

E=CmT


27/38

3) after a busy day tutoring Patrick decides to have cup of tea.Patrick fills up a mug with 200ml of water. How much energywill Patrick need to apply to change the temperature of the waterfrom 25

C to 100

C ? (Hint: for water 1ml=1g)

4)Patrick only has a kettle that can release 46Kj at a time. Howhot can he make his tea using this kettle?

5)Patrick gives up on this tea endeavour and goes to the fridge to discover his house mate has drunk

all the lemonade. He places a 375 gram lemonade in the fridge. If the energy required to cool thelemonade was found to be 42Kj were needed to cool the lemonade from 25

C to 0

C what is

the heat capacity of the lemonade?

Patrick realises it will take too long to cool the lemonade and so gives and sulks away to his roomwith his water bottle.

Finding EnthalpyWe now know that we can link energy changes or enthalpy changes to changes in temperature socan we do this in reverse to find enthalpy of some reactions. To find the enthalpy we need to firstget a calibration factor. A calibration factor only applies to a specific system and directly linkstemperature change to energy change.

E=Cf TSo to get the calibration factor Cf we must supply a known amount of energy this can be done in

two ways by using a fuel with a known amount of energy like above or to use an electric coil to

supply a known amount of energy this is done using this equation.E=VItWhere 'V' is the amount of voltage in volts, 'I' is the amount of current in amps and 't' the time inseconds the electricity is supplied.

So you can get this simply byVIt

T=Cf once you have the Cf you can use this to know how

much energy was released

6)A calorimeter is calibrated by placing 7 .00 volts at 1.60 amps for 135 seconds into thecalorimeter and recording an increase in temperature of 1.38

C . A sample of 1.54 grams of

methane was put into a calorimeter and burnt and a temperature increase of 78.10

C wasrecorded. What is the enthalpy of the combustion of methane?

substance Specific heat capacity

( J g1

C1 )

water 4.18

Oil, cooking ~2.2

Ethanol 2.4

Iron 0.47Copper 0.39

Aluminium 1.97

Sand 0.48

Heat capacities of some common materials


28/38

a) How much energy was put into the calorimeter during calibration?

b) What is the calibration factor of the calorimeter?

c) how much energy was released by the methane during this reaction?

d) how many moles of methane reacted?

e) what is the enthalpy of this reaction in Kj/mol?

Bomb calorimetersThese reactions are done in a bomb calorimeter these devices arewell insulated. To the right is an example of a combustioncalorimeter, the water itself can be used as a reactant in dilution oraqueous enthalpy measurements

Notable features are the sample storer that contains thecombustible material as well as ignition wires. There is also astirrer to make sure all the water is the same temperature and athermometer to measure the temperature. Although not in thisdiagram there is also often wires immersed in the water used forcalibration. The objective here is that as the sample chamber heats

up the water also heats up and so the temperature change can bemeasured and hence the enthalpy if a calibration factor is known.

7)What is the importance of having the system well insulated?

Energy conversion

Energy is never destroyed it only manifests in a different form. This of course means that chemicalenergy like that in a stick of dynamite can be converted into mechanical energy of moving parts.

This isn't to say that all these conversions are efficient. Some conversions are very efficient withmost of the energy being converted into the desired form whilst others are not. Here are someexamples.


29/38

Device Energy Transformation Typical efficiency (%)

Steam turbine Thermal to mechanical 45

Gas burner Chemical to thermal 85

Galvanic cell (battery) Chemical to electrical 60-90

Fuel Cell Chemical to electrical 50Generator Mechanical to electrical 90

Solar cell Light to electrical 10-14

Hot water heater (electric) Electrical to thermal Nearly 100

Electric motor Electrical to mechanical 60-90

Petrol energy Chemical to mechanical 20-25

Hydrogen engine Chemical to mechanical 25-50

Fuel Cell powered vehicle Chemical to electrical to

mechanical

20-30

Photosynthesis in a leaf Light to chemical 1

8)What is the most efficient mode of automobile transport?

The greener way

Many industrial and energy generation processes are moving to safer and more environmentalfriendly techniques.

The first principle is known as the 'atom economy' this is the method where the amount of atoms

that go into a reaction is closely matched to those that come out. If there is a way to do a reactionthat minimises the amount of waste product it is preferred. This can usually be done by carefullyselecting the way in which chemical reactions proceed.

Recycling is also a good way to go green in the chemical plant. Recycling chemicals is a commonprocess in ammonia, sulphuric acid and nitric acid production. All un-reacted chemicals are feedback into the reaction vessel for a second or third chance to react. This drastically increases theefficiency. Waste heat can also be used to heat reactions or in some cases to make electricity, manysulphuric acid plants double as power stations.

The initial reactants for a reaction can also be recycled, in the case of sulphuric acid most of the

sulphur or sulphur dioxide comes as a by product of the oil refining process. To further optimise thecollection of initial reactants some reactants can be taken from the atmosphere in sulphuric acid andnitric acid production oxidation can be done by oxygen from the air. The main reactant in ammonia

production is nitrogen also available from the air. If a reactant can be cheaply or freely resourced itis preferable.

Waste products from an industrial plant can also be reused, This is true in the case of the etheneplant by-products.

Safety is also important in this endeavour and reactions that maximise safety are important.Multiple safety precautions are required to keep the production of nitric acid safe as some products

can be explosive. There is also a step in the sulphuric acid production that is done to increase safety.


30/38

2SO3g+H2 OgH2 S2O7gThis step could be ignored however when it is ignored and SO3 is used to directly make

sulphuric acid a fine mist that is impossible to collect and dangerous to the repository system. Thisreaction to produce oleum first is used to prevent this problem

Lastly the waste that is produced whether it be actual chemicals or hot water needs to be treated

appropriately. Hot water released into a lake can actually damage the eco system and kill largeamounts of marine life. Gases exhausted into the atmosphere by power and industrial plants need to

reduce SO2, NO2,NO2 as these can react with water to form acid rain. Other waste products

must be stored or removed safetly and ecologically friendly way


31/38

Tutorial 6 - Little Rusty on RedoxThis topic on redox will have skills required in semester 1 and semester 2 of year 12 course so letstry and recap and expand a little on all of the redox we know.

What is a redox reaction? A redox reaction is one where an electron is transferred from onemolecule, atom or species to another. This is very similar to an acid base reaction where a proton is

donated or removed.

The most basic principle in redox chemistry is OIL RIG.

OIL This means that Oxidation Is Loss of electrons if something is oxidised it has lost electrons.

RIG means Reduction Is Gain if something gains electrons than it is being reduced.

However a reductant causes reduction and is itselfoxidisedwhereas an oxidant causes oxidation and is itselfreduced.

Oxidation numbersWe need a way to check if a reaction is a redox or not. We can do this by using oxidation number,the larger an oxidation number the less electrons it has. If a molecule's oxidation number changesthen it has lost or gained electrons and undergone a chemical reaction.

There are some rules for oxidation numbers(ON) and they are as follows

1. If it is a single atom with no charge the ON is 0. eg Cu ON = 0

2. An atom with valence (AKA an ion) the ON is the charge on the atom. Eg Mn+2 ON=+2

3. Hydrogen(H) has an ON of 1 and Oxygen(O) has an ON of -2

4. There are two exceptions H in NaH or hydrides H has ON of -1. In H2O2 and other peroxides

O has an ON of -1

5. Elements and ions will usually have an ON the same of their valence CO3

ON of whole thing

is -1

6. The sum of the ON's of individual atoms of a molecule need to add to the valence of thatmolecule

eg H2O valence is0=2H+O0=2+12

1)What is the oxidation number of the underlined atom in each of these molecules.Mn2+, H2SO4, Ag, NO3

-, Fe(OH)3

These oxidation numbers come in handy when you use them to determine if a reaction is oxidationor reduction. Or not redox at all


32/38

CH4g+O2gCOg+H2O l+H2g

This reaction is used to make high purity hydrogen that is sometimes used in the haber process2)What is the oxidation number of carbon in the beginning and at the end?

3) hence Is the methane oxidised or reduced?

Balancing Redox equationsBalancing redox equations requires some rules but as long as they are followed the answers shouldflow nicely.

The amount of charge on each side should always be balanced. To do this however you will have toadd negative charges to one side or the other

4) balance this half equation

Fe+2 Fe+3

When electrons appear on the left but not on the right they are being absorbed therefore the speciesis gaining electrons and it is being reduced (RIG)5) is this a reduction or an oxidation reaction

So now what if we make the formula more complex and involve the balancing of more thanelectrons. In some cases oxygen and hydrogen need to be balanced and in these cases these stepsmust be done.

1.Balance the metal atoms where needed on both sides

2.Balance the oxygen on each side of the equation by adding water when needed.

3.The hydrogens from the water must be balanced by adding H+

4.Balance the charges by adding electrons where needed

6) Test these skills by balancing this equation

MnO41 Mn+2

We now have two half equations which can be added together to get a full equation. To do this theremust be the same number of electrons on both sides which means that first the electrons must be onopposite sides of the equation and they must have the same amount of electrons.


33/38

7)a Of the above equations which is oxidation and which is reduction

b Combine the above half equations to form a full equation

Strong vs weakWhy cant the above reaction be written backwards? The answer is it can but it only actually worksthe way it is written. The reason for that is the driving force of the reaction.

Strong oxidants and strong reductants react to form weak oxidants and weakreductants.

1

2F2+2e

2F

Ag+ +e Ag

Mg+2+2 e Mg

Li+ +e Li

Above is a small portion of the electrochemical series but lets break down the series first which sidecontain oxidants and which reductants?8)Label each side here and in the back of the book.

Now what do we know about these chemicals we know that Lithium (Li) is in the first period of theperiodic table. Lithium really wants to get rid of its electrons to have a full shell and hence is veryelectro positive12. This means that it is a strong reductant (the reductant undergoes oxidation OIL).

Li+

Does not want to gain electrons because it is stable with a full shell so it is a weak oxidant.

Flourine (F) is similar it really wants an extra electron to have a full shell so is a very strong oxidantas it really wants to be reduced. In this way the reduction strength and the oxidation strength changein the series.

9) draw in each side here and in the back of the book increasing oxidation and reduction strength.

A sample containing silver and magnessium as well as their ions would react. The strongest oxidantwould be the Ag+ and it would react with the strongest reductant being Mg. By doing this we see aline making a backward Z forms. If this cant be done then the reaction will not proceedspontaneously.10)Draw this on the above chart and state the final products of the reaction

12 The lithium is not a person and doesnt actually want elections I just find it easer to explain this way


34/38

11) would a reaction occur with these reactants and if not why?Zinc ions and copper ions dissolved in solution

Aluminum metal in the presence of Chlorine gas

Lead metal and Cobolt ions in a solution

Gold ions and iodide ions in a solution

Now to discuss making half cells. If a redox reaction is spontaneous it is exothermic, meaning thatit will release energy. The nature of these reactions lends itself to having the energy be harness-able

by forcing the oxidised electrons to pass through a wire before reacting.

12)Take copper and copper sulphate was made into a galvanic cell with zinc nitrate and zinc metal

a)What are the half cell reactions

b) which of the two half equations are oxidative and which reductive?

c) write the full equation for this galvanic cell

d) what is the oxidant and what is the reductant

Before drawing the galvanic cell the importance of electrodes must be discussed. An electrode is thepoint where electrons are passed into or out of the solution. Electrodes are usually solid and can beinert or act in the reaction.

The electrode where oxidation occurs is known as the anode and the reaction where the reductionoccurs is the cathode, this is always true. In a galvanic spontaneous reaction the oxidant looseselectrons so it will be negative due to excess electrons. An OIL RIG Cat (this is a memory trick)

e) What is the importance of a salt bridge in a galvanic cell.


35/38

f)draw the galvanic cell set-up bellow (include: electron flow, saltbridge ion migration, oxidant andreductant labels, label each electrode as anode and cathode and their charge)

Electrochemical cellsSo what happens if we reverse the poles on a battery. We can force nature backwards by supplyingenergy and what were weak reductants and weak oxidants become strong oxidants and strongreductants.

Any spontaneous galvanic cell can be reversed by supplying energy to the reaction. This is done byhaving the terminals of a battery forcibly charged.

Fes+Pbaq+2Feaq

+2+Pbs

This reaction is a spontaneous galvanic reaction. It can be reversed to return to the reactants. Iron inthis case is loosing electrons and hence is being oxidised and is the oxidant. In order to reverse thereaction the iron will need to accept electrons. This will allow the iron to be reduced and hence bethe cathode. To force the electrons onto the iron the iron must be positively charged.

Feaq+2+PbsFes+Pbaq

+2

A electrochemical reaction does not need a salt bridge and can completely occur in one beaker withone solution.

13)Draw the electrochemical cell setup bellow (include: electron flow, ion migration, oxidant andreductant labels, label each electrode as anode and cathode and their charge)

14)What happens to the electrodes during this reaction?


36/38

ElectroplatingTake a solution of silver ions and place a graphite rod into this solution and attach it to a batteryforcing electrons into it. The electrons will combine with the silver ions and form a layer or silveron the surface of the carbon. This is the basic principle of electroplating.

14)Two solutions are made one containing silver ions the other containing nickel ions. If the same

amount of charge is placed into both which will have the greater amount of atoms in the coating?Why?

Current is measured in amperes and is the number of electrons per a second measured in Coulombs.By measuring the current and the time the battery is connected we can find the amount of electronsthat went into a solution in coulombs.

Q=It

Now if only there was a way to link the amount of electrons into something we can use like mole and then came Faraday who did just that with 96485 coulombs per a mole.

n (electrons )=Q

F

We now have enough to know how much of something is electroplated BUT as before rememberthat even though for example 1 mole of electrons goes into the solution only 0.333 moles ofaluminium could be platedwhy?

15) A carbon electrode is placed in a concentrated copper sulphate solution. If a current of 10ampsis applied to the rod for 5 minutes what weight of copper will form on the electrode.13

13 Thats it I hope you enjoyed the book and found it useful. Good luck in year 12


37/38

Appendix relevant data


38/38

Documents

chemistryyr12