Preparing to Study A Level Chemistry 2020 · This resource “Preparing to Study A Level Chemistry”, is a derivative of “Starters for ten – Transition skills 0.2” by The Royal

Preparing to Study

A Level Chemistry

(OCR)

Mrs Tiernan Subject Leader for Science

Miss Tighe Assistant Subject Leader - Chemistry

This resource “Preparing to Study A Level Chemistry”, is a derivative of “Starters for ten – Transition skills 0.2” by The Royal Society of Chemistry used under CC-BY-NC-SA 4.0. “Preparing to Study A Level Chemistry”, is licensed under CC-BY-NC-SA 4.0. Images © Shutterstock.

CONTENTS

1. A level chemistry at the Campion school 2. Introduction 3. Transition skills 4. Useful information 5. Research activities 6. Answers to the transition skills


A-Level Chemistry at the Campion School

• Exam Board Entry Requirements Subject Leader

OCR Grade 6 at GCSE Chemistry Grade 7-6 at GCSE Combined Science Grade 6 at GCSE Mathematics

Ms. L Tighe

Qualification OCR A level Chemistry B (Salters) Download the syllabus and become familiar with the organisation of the course and how the course is assessed https://www.ocr.org.uk/qualifications/as-and-a-level/chemistry-b-salters-h033-h433-from-2015/ Is this the right subject for me? Chemistry is suitable if you:

• Have an interest in, and enjoy chemistry • Want to link chemical concepts together to develop your understanding behind chemical content

within the context. • Want to develop chemical literacy skills by extracting and manipulating data, interpreting and using

information. • Enjoy showing comprehension by written communication with regard to logical presentation and

correct use of technical terms • Enjoy carrying out practical investigations • Want to study chemistry further in Higher Education, to support other qualifications or enter a

chemistry based career


Introduction Most students find the transition from GCSE to A-level Chemistry very challenging. To help make this transition smoother and to give you the best possible start, we have prepared this booklet for you.

This booklet contains three areas, or competencies, each covering the understanding most pupils will need to develop in order to access the A-level course.

The first, Basic chemistry competencies, explores ideas around atoms, chemical formulae and equations.

The second competency, Basic mathematical competencies. The questions explore all kinds of broad scientific concepts, always keeping maths at the centre of the problem.

Finally, the third competency looks at practical skills.

To help you complete this booklet the following resources may be useful: • http://www.bbc.co.uk/schools/gcsebitesize/ • http://www.s-cool.co.uk/gcse • Any GCSE Additional Science/ Chemistry revision guide • Your own old GCSE Science/ Chemistry exercise books


Starters for 10 – Transition skills 0.1.1 Balancing equations

Balance the equations below.

1. …..C + …..O2 …..CO

2. …..Ba + …..H2O …..Ba(OH)2 + …..H2

3. …..C2H6 + …..O2 …..CO2 + …..H2O

4. …..HCl + …..Mg(OH)2 …..MgCl2 + H2O

5. …..N2 + …..O2 …..NO

6. …..Fe2O3 + …..C …..Fe + …..CO2

7. …..CH3CH2OH + …..[O] …..CH3COOH + …..H2O

8. …..HNO3 + …..CuO …..Cu(NO3)2 + H2O

9. …..Al3+ + …..e– …..Al

10. …..[Fe(H2O)6]3+ + …..CO32– …..Fe(OH)3(H2O)3 + …..CO2 + …..H2O

(10 marks)


Starters for 10 – Transition skills 0.1.2 Constructing ionic formulae 1. For each of the following ionic salts, determine the cation and anion present and use these to

construct the formula of the salt. (5 marks) a. Magnesium oxide b. Sodium sulfate c. Calcium hydroxide d. Aluminium oxide e. Copper(I) oxide

2. When an acid is added to water it dissociates to form H+ ions (which make it acidic) and an

anion. These acidic hydrogen atoms can be used to determine the charge on the anion. Deduce the charge on the anions in the following acids. The acidic H atoms, H+, have been

underlined for you. (5 marks) a. H2SO3 b. HNO3 c. H3PO4 d. HCOOH e. H2CO3


Starters for 10 – Transition skills 0.1.3 Writing equations from text

The following questions contain a written description of a reaction. In some cases the products may be missing as you will be expected to predict the product using your prior knowledge.

For more advanced equations you may be given some of the formulae you need.

For each one, write a balanced symbol equation for the process. (10 marks)

1. The reaction between silicon and nitrogen to form silicon nitride Si3N4. .................................................................................................................................................

2. The neutralisation of sulfuric acid with sodium hydroxide.

.................................................................................................................................................

3. The preparation of boron trichloride from its elements.

.................................................................................................................................................

4. The reaction of nitrogen and oxygen to form nitrogen monoxide.

.................................................................................................................................................

5. The combustion of ethanol (C2H5OH) to form carbon dioxide and water only.

.................................................................................................................................................

6. The formation of silicon tetrachloride (SiCl4) from SiO2 using chlorine gas and carbon.

.................................................................................................................................................

7. The extraction of iron from iron(III) oxide (Fe2O3) using carbon monoxide.

.................................................................................................................................................

8. The complete combustion of methane.

.................................................................................................................................................

9. The formation of one molecule of ClF3 from chlorine and fluorine molecules.

.................................................................................................................................................

10. The reaction of nitrogen dioxide with water and oxygen to form nitric acid.

.................................................................................................................................................


Starters for 10 – Transition skills 0.2.1 Rearranging equations 1. The amount of substance in moles (n) in a solution can be calculated when the concentration

given in mol/dm3 (c) and volume (v) in cm3 are known by using the equation:

n=cv1000

a. Rearrange this equation making c the subject of the equation. (1 mark) b. Rearrange this equation making v the subject of the equation. (1 mark)

2. The density of a substance can be calculated from its mass (m) and volume (v) using the

equation:

d=mv

a. Rearrange this equation so that the mass of a substance can be calculated given its density and volume. (1 mark)

Chemists most commonly work with masses expressed in grams and volumes in cm3. However, the SI unit for density is kg/m3. b. Write an expression for the calculation of density in the SI unit of kg/m3 when the mass (m)

of the substance is given in g and the volume (v) of the substance is given in cm3. (2 marks)

3. The de Broglie relationship relates the wavelength of a moving particle (λ) with its momentum

(p) through Planck’s constant (h):

λ=hp

a. Rearrange this equation to make momentum (p) the subject of the formula. (1 mark) Momentum can be calculated from mass and velocity using the following equation.

p=mvb. Using this equation and the de Broglie relationship, deduce the equation for the velocity of

the particle. (2 marks)

4. The kinetic energy (KE) of a particle in a time of flight mass spectrometer can be calculated using the following equation.

KE=12mv2

Rearrange this equation to make v the subject of the equation. (2 marks)


Starters for 10 – Transition skills 0.2.2 BODMAS (order of operations)

The order of operations for a calculation is very important. If operations are carried out in the wrong order then this could lead to the wrong answer. Most modern calculators will anticipate BODMAS issues when operations are entered but human beings can override the calculator’s instincts.

1. Do the following calculations in your head.

(a) 3 + 5 × 5 =

(b) 6 × 6 + 4 =

(c) 20 – 6 × 2 =

(d) 48 – 12 ÷ 4 =

(e) 4 + 4 ÷ 2 =

(f) 100 – (20 × 3) =

(6 marks)

2. The molecular formula of glucose is C6H12O6. Three students entered the following into their calculators to calculate the relative formula mass of glucose. Repeat their calculations as shown.

(a)

(b)

(c)

(d) Write a sentence summing up why the answers differ.

(4 marks)

12 × 6 + × 12 + 16 × 6 = 1

( 12 × 6 + 12 × 1 ) + )

12 × 6 = 1 = × 12 = + 16 +

= × 6 =

16 × 6 = (

(

)


Starters for 10 – Transition skills 0.2.3 Quantity calculus (unit determination)

1. Determine the units of density given that

𝑑𝑒𝑛𝑠𝑖𝑡𝑦 =𝑚𝑎𝑠𝑠(𝑔)

𝑣𝑜𝑙𝑢𝑚𝑒(𝑐𝑚")

(1 mark)

2. Determine the units of concentration given that

𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑛𝑢𝑚𝑏𝑒𝑟𝑜𝑓𝑚𝑜𝑙𝑒𝑠(𝑚𝑜𝑙)

𝑣𝑜𝑙𝑢𝑚𝑒(𝑑𝑚")

(1 mark)

3. Pharmacists often calculate the concentration of substances for dosages. In this case the volumes are smaller, measured in cm3, and the amount is given as a mass in grams. Determine the units of concentration when

𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑚𝑎𝑠𝑠(𝑔)

𝑣𝑜𝑙𝑢𝑚𝑒(𝑐𝑚")

(1 mark)

4. Rate of reaction is defined as the ‘change in concentration per unit time’. Determine the units for rate when concentration is measured in mol dm–3 and time in seconds.

(1 mark)

5. Pressure is commonly quoted in pascals (Pa) and can be calculated using the formula below. The SI unit of force is newtons (N) and area is m2.

𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 𝑓𝑜𝑟𝑐𝑒𝑎𝑟𝑒𝑎

Use this formula to determine the SI unit of pressure that is equivalent to the Pascal.

(1 mark)

6. Determine the units for each of the following constants (K) by substituting the units for each part of the formula into the expression and cancelling when appropriate. For this exercise you will need the following units [ ] = mol dm–3, rate = mol dm–3 s–1, p = kPa.

a. 𝐾# =[%][']!

[(]

b. 𝐾 = )*+,[%][']

c. 𝐾-

(-%)".$

(-')

d. 𝐾0 = [𝐻1][𝑂𝐻2]

e. 𝐾* =

[3%][5&][35]


Starters for 10 – Transition skills 0.2.4 Expressing large and small numbers

Standard form and scientific form Large and small numbers are often expressed using powers of ten to show their magnitude. This saves us from writing lots of zeros, expresses the numbers more concisely and helps us to compare them.

In standard form a number is expressed as;

a × 10n

where a is a number between 1 and 10 and n is an integer.

Eg, 160 000 would be expressed as 1.6 × 105

Sometimes scientists want to express numbers using the same power of ten. This is especially useful when putting results onto a graph axis. This isn’t true standard form as the number could be smaller than 1 or larger than 10. This is more correctly called scientific form.

Eg, 0.9 × 10–2, 2.6 × 10–2, 25.1 × 10–2 and 101.6 × 10–2 are all in the same scientific form.

1. Express the following numbers using standard form.

a. 1 060 000 b. 0.001 06 c. 222.2

(3 marks)

2. The following numbers were obtained in rate experiments and the students would like to express them all on the same graph axes. Adjust the numbers to a suitable scientific form.

(3 marks)

3. Calculate the following without using a calculator. Express all values in standard form.

a. 67'

67$

b. 67(

67&(

c. !.#×!&!

#.'×!&"#

d. (2.0 × 10() × (1.2 × 10)*)

(4 marks)

0.1000 0.0943 0.03984 0.00163


Starters for 10 – Transition skills 0.2.5 Significant figures, decimal places and rounding

For each of the numbers in questions 1–6, state the number of significant figures and the number of decimal places.

Significant figures

Decimal places

1 3.131 88

2 1000

3 0.000 65

4 1006

5 560.0

6 0.000 480

(6 marks)

7. Round the following numbers to (i) 3 significant figures and (ii) 2 decimal places.

a. 0.075 84 b. 231.456

(4 marks)


Starters for 10 – Transition skills 0.2.6 Unit conversions 1 – Length, mass and time

Mo’s teacher has drawn a diagram on the board to help him with converting quantities from one unit into another.

For example, to convert a length in millimetres into units of centimetres, divide by 10,

eg 10 mm = 1 cm.

Use the diagram to help with the following unit conversions. (10 marks)

1. A block of iron has a length of 1.2 cm. Calculate its length in millimetres.

2. The width of the classroom is 7200 cm. Calculate its length in metres.

3. A reaction reaches completion after 4½ minutes. Convert this time into seconds.

4. The stop clock reads 2 min 34 s. Convert this time into seconds.

5. A method states that a reaction needs to be heated under reflux for 145 min. Calculate this time in hours and minutes.

6. A factory produces 15 500 kg of ammonia a day. Calculate the mass of ammonia in tonnes.

7. A paper reports that 0.0265 kg of copper oxide was added to an excess of sulfuric acid. Convert this mass of copper oxide into grams.

8. A packet of aspirin tablets states that each tablet contains 75 mg of aspirin. Calculate the minimum number of tablets that contain a total of 1 g of aspirin.

9. A student measures a reaction rate to be 0.5 g/s. Convert the rate into units of g/min.

10. A factory reports that it produces fertiliser at a rate of 10.44 kg/h. Calculate the rate in units of g/s.


Starters for 10 – Transition skills 0.2.7 Unit conversions 2 – Volume

The SI unit for volume is metre cubed, m3. However as volumes in chemistry are often smaller than 1 m3, fractions of this unit are used as an alternative.

centimetre cubed, cm3 decimetre cubed, dm3

centi- prefix one hundredth deci- prefix one tenth

1 cm = $$%%

m so, 1 dm = $$%

m so,

1 cm3 = ! $$%%"3 m3 = ! $

$%%%%%%"m3 1 dm3 = ! $

$%"3 m3 = ! $

$%%%"m3

1. Complete the table by choosing the approximate volume from the options in bold for each of

the everyday items (images not drawn to scale). (1 mark) 1 cm3 1 dm3 1 m3

drinks bottle sugar cube washing machine

Approx. volume

2. Complete the following sentences; (1 mark)

To convert a volume in cm3 into a volume in dm3, divide by .............................. To convert a volume in cm3 into a volume in m3, divide by ................................

3. a. A balloon of helium has a volume of 1600 cm3. What is its volume in units of dm3? b. The technician has prepared 550 cm3 of HCl(aq). What is its volume in units of m3? c. An experimental method requires 1.35 dm3 of NaOH(aq). What volume is this in cm3? d. A swimming pool has a volume of 375 m3. What volume is this in cm3? e. A 12 g cylinder of CO2 contains 6.54 dm3 of gas. What volume of gas is this in units of m3? (5 marks) 4. Which cylinder of propane gas is the best value for money? (3 marks)

a. b. c.

2.13 × 106 cm3

of propane for £15.49

2700 dm3 of propane for £21.25

7 m3

of propane for £28.75


Starters for 10 – Transition skills 0.2.8 Moles and mass One mole of a substance is equal to 6.02 × 1023 atoms, ions or particles of that substance. This number is called the Avogadro constant.

The value of the Avogadro constant was chosen so that the relative formula mass of a substance weighed out in grams is known to contain exactly 6.02 × 1023 particles. We call this mass its molar mass.

We can use the equation below when calculating an amount in moles:

amount of substance (mol) = mass (g)

molar mass (g mol–1)

Use the equation above to help you answer the following questions.

1. Calculate the amount of substance, in moles, in: (3 marks) a. 32 g of methane, CH4 (molar mass, 16.0 g mol–1) b. 175 g of calcium carbonate, CaCO3 c. 200 mg of aspirin, C9H8O4 2. Calculate the mass in grams of: (3 marks) a. 20 moles of glucose molecules (molar mass, 180 g mol–1) b. 5.00 × 10–3 moles of copper ions, Cu2+ c. 42.0 moles of hydrated copper sulfate, CuSO4•5H2O 3. a. 3.09 g of a transition metal carbonate was known to contain 0.0250 mol. i. Determine the molar mass of the transition metal carbonate. (1 mark) ii. Choose the most likely identity for the transition metal carbonate from the list below:

CoCO3 CuCO3 ZnCO3 (1 mark)

b. 4.26 g of a sample of chromium carbonate was known to contain 0.015 mol. Which of the following is the correct formula for the chromium carbonate? (2 marks)

CrCO3 Cr2(CO3)3 Cr(CO3)3

BONUS QUESTION

If you had 1 mole of pennies which you could share with every person on earth how much could you give each person? Approximate world population = 7 500 000 000.

Stating the amount of substance in moles is just the same as describing a quantity of eggs in dozens. You could say you had 24 or 2 dozen eggs.

How is a mole similar to a dozen?

This resource “new name”, is a derivative of “Starters for ten – Transition skills answers” by The Royal Society of Chemistry used under CC-BY-NC-SA 4.0. “new name” is licensed under CC-BY-NC-SA 4.0 by “name of user”.

Starters for 10 – Transition skills 0.2.9 Moles and concentration

To calculate the concentration of a solution we use the equation:

concentration (mol dm–3) = amount of substance

(mol) volume (dm3)

Use the equation to help you complete each of the statements in the questions below.

1. a. 1.5 mol of NaCl dissolved in 0.25 dm3 of water produces a solution with a concentration

of .................................. mol dm–3. (1 mark)

b. 250 cm3 of a solution of HCl(aq) with a concentration of 0.0150 mol dm–3 contains

..................................... moles. (1 mark)

c. A solution with a concentration of 0.85 mol dm–3 that contains 0.125 mol has a volume of

........................................ dm3. (1 mark) 2. In this question you will need to convert between an amount in moles and a mass as well as

using the equation above.

Space for working is given beneath each question.

a. 5.0 g of NaHCO3 dissolved in 100 cm3 of water produces a solution with a concentration

of ............................ mol dm–3. (2 marks)

b. 25.0 cm3 of a solution of NaOH(aq) with a concentration of 3.8 mol dm–3 contains

.............................. g of NaOH. (2 marks)

c. The volume of a solution of cobalt(II) chloride, CoCl2, with a concentration of 1.3 mol dm–3

that contains 2.5 g of CoCl2 is ....................... cm3. (3 marks)


Starters for 10 – Transition skills 0.3.1 Laboratory equipment

Practical work is a key aspect in the work of a chemist.

To help you plan effective practical work it is important that you are familiar with the common laboratory equipment available to you.

1. For each of the pieces of glassware shown in the images below, state their name and give a possible volume(s).

a. Name: b. Name:

..............................................................................................................

Possible volume(s): Possible volume(s):

..............................................................................................................

c. Name: d. Name:

..............................................................................................................


..............................................................................................................

e. Name: f. Name:

..............................................................................................................


..............................................................................................................

(6 marks)

2. Name the common laboratory equipment in the images below. (4 marks)

a. b. c.

..........................................................................................................................................

d.


Starters for 10 – Transition skills 0.3.2 Recording results

1. A student is looking at endothermic processes. He adds 2.0 g of ammonium nitrate to 50 cm3

of water and measures the temperature change. He repeats the experiment three times.

His results are shown in the table below.

Temperature at start

Temperature at end

Temperature change

Run 1 21.0 –1.1 22.1

Run 2 20 –2 22

Run 3 20.2 2 18.2

Mean 22.05

Annotate the table to suggest five ways in which the table layout and the recording and analysis of his results could be improved. (5 marks)

2. For each of the experiments described below, design a table to record the results.

Experiment 1: Simon is investigating mass changes during chemical reactions. He investigates the change in mass when magnesium ribbon is oxidised to form magnesium oxide:

magnesium + oxygen ® magnesium oxide

He records the mass of an empty crucible. He places a 10 cm strip of magnesium ribbon in the crucible and records the new mass of the crucible. He heats the crucible strongly until all the magnesium ribbon has reacted to form magnesium oxide. He allows the crucible to cool before recording the mass of the crucible and magnesium oxide.

Experiment 2: Nadiya is investigating how the rate of a reaction is affected by concentration. She investigates the reaction between magnesium ribbon and hydrochloric acid.

magnesium + hydrochloric acid ® magnesium chloride + hydrogen

She places 25 cm3 of hydrochloric acid with a concentration of 0.5 mol dm–3 into a conical flask and fits a gas syringe. She adds a 3.0 cm strip of magnesium ribbon and measures the volume of hydrogen gas produced every 20 s for 3 minutes.

She repeats the experiment with hydrochloric acid with concentrations of 1.0 mol dm–3 and then 1.5 mol dm–3. (5 marks)

Starters for 10 – Transition skills


0.3.3 Drawing scatter graphs

When you want to find a correlation between two variables it is helpful to draw a scatter graph.

Key points to remember when drawing scatter graphs include:

• The independent variable (the variable that is changed) goes on the x-axis and the dependent variable (the variable you measured) goes on the y-axis.

• The plotted points must cover more than half the graph paper.

• The axes scales don’t need to start at zero.

• A straight line or smooth curve of best fit is drawn through the points to show any correlation.

Karina is investigating the relationship between the volume of a gas and its temperature. She injects 0.2 cm3 of liquid pentane (b.p. 36.1 °C) into a gas syringe submerged in a water bath at 40 °C. After 5 minutes she measures the volume of gas in the syringe. She repeats the experiment three times with the water bath at 40 °C.

She then repeats the experiment for temperatures of 50, 60, 70 and 80 °C.

Her results are shown in the table below:

Temperature / °C Volume of gas / cm3

Run 1 Run 2 Run 3 Mean

40 40.8 43.1 42.7 42.2

50 46.1 46.2 46.9 46.4

60 54.7 48.1 48.3 48.2

70 49.1 49.6 49.5 49.4

80 51.0 47.3 51.0 51.0

1. Plot a scatter graph of the volume of the gas against the temperature. (6 marks)

2. Add error bars to show the range of readings used to calculate the mean volume of the gas at each temperature. (2 marks)

3. Draw in a line of best fit. (1 mark)

4. Describe the correlation observed. (1 mark)


Other useful resources

Studying A levels require note taking. Cornell notes is a good technique to use. See the link below

http://coe.jmu.edu/learningtoolbox/cornellnotes.html

This Head Start book is perfect for helping you get off to a flying start in A-Level Chemistry… and it’s suitable for all exam boards! It recaps all the crucial topics you’ll need to remember from GCSE, with crystal-clear study notes and examples, plus practice questions to test your understanding. What’s more, we’ve included introductions to some of the most important A-Level topics. Brilliant for preparation work over the summer before you start at sixth form!

This book can also be bought as a standalone Online Edition

https://www.cgpbooks.co.uk/search-results?searchtext=head%2Bstart%2B&searchmode=anyword&active_tab=product

Calculations in AS/A Level Chemistry (Paperback) Jim Clark

ISBN-10: 0582411270

If you struggle with the calculations side of chemistry, this is the book for you. Covers all the possible calculations you are ever likely to come across. Brought to you by the same guy who wrote the excellent chemguide.co.uk website.


Research activities Use your online searching abilities to see if you can find out as much about the topic as you can. Remember it you are a prospective A level chemist, you should aim to push your knowledge.

You can make a 1-page summary for each one you research using Cornell notes:

http://coe.jmu.edu/learningtoolbox/cornellnotes.html

Task 1: The chemistry of fireworks

What are the component parts of fireworks? What chemical compounds cause fireworks to explode? What chemical compounds are responsible for the colour of fireworks?

Task 2: Why is copper sulfate blue?

Copper compounds like many of the transition metal compounds have got vivid and distinctive colours – but why?

Task 3: Aspirin

What was the history of the discovery of aspirin, how do we manufacture aspirin in a modern chemical process?

Task 4: The hole in the ozone layer

Why did we get a hole in the ozone layer? What chemicals were responsible for it? Why were we producing so many of these chemicals? What is the chemistry behind the ozone destruction?

Task 5: ITO and the future of touch screen devices

ITO – indium tin oxide is the main component of touch screen in phones and tablets. The element indium is a rare element and we are rapidly running out of it. Chemists are desperately trying to find a more readily available replacement for it. What advances have chemists made in finding a replacement for it?


Starters for 10 Transition skills answers

0.1 Basic chemistry competencies

0.1.1. Balancing equations

Accept multiples or appropriate fractions, 1 mark each.

1. 2C + …..O2 2CO

2. …..2Ba + ….2H2O 2Ba(OH)2 + …..H2

3. …..C2H6 + 3.5O2 2CO2 + 3H2O

4. 2HCl + …..Mg(OH)2 …..MgCl2 + 2H2O

5. …..N2 + …..O2 2NO

6. 2Fe2O3 + …3C 4Fe + 3CO2

7. …..CH3CH2OH + 2[O] …..CH3COOH + …..H2O

8. 2HNO3 + …..CuO …..Cu(NO3)2 + H2O

9. …..Al3+ + 3e– …..Al

10. 2Fe(H2O)63+ + 3CO3

2– 2Fe(OH)3(H2O)3 + 3CO2 + 3H2O

0.1.2. Constructing ionic formulae

1.

a. Mg2+ O2– = MgO (1 mark)

b. Na+ SO42– = Na2SO4 (1 mark)

c. Ca2+ OH– = Ca(OH)2 (1 mark)

d. Al3+ O2– = Al2O3 (1 mark)

e. Cu+ O2– = Cu2O (1 mark)


2.

a. SO42– (1 mark)

b. NO3– (1 mark)

c. PO43– (1 mark)

d. HCOO– (1 mark)

e. CO32– (1 mark)

0.1.3. Writing equations from text

1 mark each, accept multiples for all except question 9.

1. 3Si + 2N2 Si3N4

2. H2SO4 + 2NaOH Na2SO4 + 2H2O

3. B + 1.5Cl2 BCl3

4. N2 + O2 2NO

5. C2H5OH + 3O2 2CO2 + 3H2O

6. SiO2 + C + 2Cl2 SiCl4 + CO2

7. Fe2O3 + 3CO 2Fe + 3CO2

8. CH4 + 2O2 CO2 + 2H2O

9. 0.5Cl2 + 1.5F2 ClF3

10. 2NO2 + H2O + 0.5O2

2HNO3


0.2 Basic mathematical competencies

0.2.1. Rearranging equations

1.

a. 𝑐 = $%%%'(

(1 mark)

b. 𝑣 = $%%%')

(1 mark)

2.

a. 𝑚 = 𝑑 × 𝑣 (1 mark)

b. 𝑑 = *+$%!"

(+$%!# = *

(+$%!"

1 mark for both parts of the fraction correct, 1 mark for cancelling down the × 10–6 to × 10–3. (2 marks)

3.

a. 𝑝 = ,- (1 mark)

b. 𝑣 = ,-*

1 mark for substitution of p = mv into the first equation and 1 mark for successful rearrangement.

(2 marks)

4.

𝑣 = + ./%.1*

or 𝑣 = +2./*

1 mark for first rearrangement moving 0.5 m underneath the KE, 1 mark for dealing with the v2 by addition of the square root. (2 marks)

0.2.2. BODMAS

1. a. 28

b. 40

c. 8

d. 45

e. 6

f. 40


2. a. 180 (1 mark)

b. 5352 (1 mark)

c. 180 (1 mark)

Evaluation: Pressing equals after each operation leads to BODMAS errors. (1 mark)

0.2.3. Quantity calculus

1. g cm–3 (1 mark)

2. mol dm–3 (1 mark)

3. g cm–3 (1 mark)

4. mol dm–3 s–1 (1 mark)

5. N m–2 (1 mark)

6. a. mol2 dm–6 (1 mark)

b. mol–1 dm3 s–1 (1 mark)

c. kPa–0.5 (1 mark)

d. mol2 dm–6 (1 mark)

e. mol dm–3 (1 mark)


0.2.4. Expressing large and small numbers

1. a. 1.06 × 106 (1 mark)

b. 1.06 × 10–3 (1 mark)

c. 2.222 × 102 (1 mark)

2. 1 mark for sensible choice of × 10x power, in this case × 10–2 or × 10–3 is most sensible. 0.5 marks for each number correctly converted.

3. a. 104 (1 mark)

b. 1014 (1 mark)

c. 0.5 × 10–11 or 5 × 10–12 (1 mark)

d. 2.4 × 102 (1 mark)

0.2.5. Significant figures, decimal places and rounding

Significant figures

Decimal places

1 3.131 88 6 5

2 1000 1 0

3 0.000 65 2 5

4 1006 4 0

5 560.0 4 1

6 0.000 480 3 6

(0.5 mark for each correct answer)

7. a. i. 0.0758 (1 mark) ii. 0.08 (1 mark) b. i. 231 (1 mark) ii. 231.46 (1 mark)


0.2.6. Unit conversions 1 – Length, mass and time

1. 12 mm (1 mark)

2. 72.00 m (1 mark)

3. 270 s (1 mark)

4. 154 s (1 mark)

5. 2 h 25 min (1 mark)

6. 15.5 t (1 mark)

7. 26.5 g (1 mark)

8. 75 mg/tablet = 0.075 g/tablet 1 g ÷ 0.075 g/tablet = 13.3 tablets Minimum number of tablets needed = 14 (1

mark)

9. 30 g/min (1 mark)

NOTE In this example, as you are converting 1/the unit, you need to do the inverse of what is described in the diagram eg instead of ÷ 60, × 60.

10. 10.44 kg/h = 10 440 g/h = 174 g/min = 2.9 g/s (1 mark)

0.2.7. Unit conversions 2 – Volume

1. drinks bottle, 1 dm3; sugar cube, 1 cm3; washing machine, 1 m3 (1 mark)

2. To convert a volume in cm3 into a volume in dm3, divide by 1000. (½ mark) To convert a volume in cm3 into a volume in m3, divide by 1 000 000. (½ mark)

3. a. 1.6 dm3 (1 mark)

b. 5.5 × 10–4 m3 (1 mark)

c. 1350 cm3 (1 mark)

d. 375 000 000 cm3 (1 mark)


e. 0.006 54 m3 (1 mark)

4. (1 mark) (1 mark) (1

mark)

Therefore ‘c’ is the best value for money.

0.2.8. Moles and mass

1. a. 32.0 g ÷ 16.0 g mol–1 = 2 mol (1 mark) b. 175 g ÷ 100.1 g mol–1 = 1.75 mol (1 mark) c. 0.2 g ÷ 180.0 g mol–1 = 0.0011 mol (1 mark)

2. a 20 mol × 180 g mol–1 = 3 600 g (1 mark) b 5.00 × 10–3 mol × 63.5 g mol–1 = 0.318 g (1 mark) c 42.0 mol × 249.6 g mol–1 = 10 500 g (1 mark)

3. a. i. 3.09 g ÷ 0.0250 mol = 123.6 g mol–1 (1 mark)

ii. CuCO3 (1 mark)

b. molar mass of chromium carbonate = 4.26 g ÷ 0.015 mol = 284 g mol–1 (1 mark)

Cr2(CO3) (1 mark)

BONUS QUESTION

£ per m3 p per cm3 p per dm3

Cylinder ‘a’ 7.27 or 7.27 × 10–4 or 0.727 Cylinder ‘b’ 7.87 7.87 × 10–4 0.787 Cylinder ‘c’ 4.11 4.11 × 10–4 0.411


6.02 × 1023 p ÷ 7 500 000 000 people = 8.03 × 1013 p per person or 803 000 million pounds per person!

0.2.9. Moles and concentration

1. a. 1.5 mol ÷ 0.25 dm3 = 6.0 mol dm–3 (1 mark) b. 0.25 dm3 × 0.0150 mol dm–3 = 3.75 × 10–3 mol (1 mark) c. 0.125 mol ÷ 0.85 mol dm–3 = 0.15 dm3 (1 mark)

2. a. 5.0 g ÷ 84.0 g mol–1 = 0.0595 mol (1 mark) 0.0595 mol ÷ 0.100 dm3 = 0.60 mol dm–3 (1 mark) b. 0.025 dm3 × 3.8 mol dm–3 = 0.095 mol (1 mark) 0.095 mol × 40.0 g mol–1 = 3.8 g (1 mark) c. 2.5 g ÷ 129.9 g mol–1 = 0.0192 mol (1 mark) 0.0192 mol ÷ 1.3 mol dm–3 = 0.015 dm3 (1 mark) 0.0148 dm3 = 15 cm3 (to 2 sig. fig.) (1 mark)

0.3 Basic practical competencies

0.3.1. Laboratory equipment


1. For each part (a)–(e) give ½ mark for the correct name and ½ mark for one or more correct possible volumes depending on what is available in your laboratory.

a. conical flask 100 cm3 / 250 cm3 b. beaker 100 cm3 / 250 cm3

c. volumetric flask 100 cm3 / 200 cm3 / 250 cm3 d. test tube or boiling tube 10 cm3 or 25 cm3 e. burette 50 cm3 f. pipette various sizes although 20 cm3 or 25 cm3 are the most common at school level 2. a. (gas) syringe (1 mark) b. evaporating basin (1 mark) c. crucible (1 mark) d. pestle and mortar (the mortar is the bowl) (1 mark)

0.3.2. Recording results

1. Improvements: (1 mark for each improvement identified)

• Units for temperature should be included in the table headings. • All results should be recorded to the same number of decimal places (the resolution of the

thermometer used), in this case 1 d.p. • The temperature changes are negative and so should be recorded as such, eg –22.1, or the

heading should be changed to ‘Temperature decrease’ or similar. • The temperature change for Run 3 is anomalous and so should be circled, or similar, to show

this. It is correctly not included in the calculation of the mean. • The mean temperature change should be stated to the same number of significant figures as

the values from which it is calculated.

2. Experiment 1: (2 marks)


Mass / g

Crucible empty

Crucible + magnesium ribbon

Crucible + magnesium oxide

1 mark – Units given in table heading 1 mark – Clear description of item of which the mass is being

recorded Use teacher discretion to award marks for other suitable tables

Experiment 2: (3 marks)

Time / s

Volume of hydrogen gas produced / cm3

0.5 mol dm–3 HCl(aq)



0

20

40

60

80

100

120

140

160

180

1 mark – Columns clearly labelled with units 1 mark – Dependent variable (volume of hydrogen gas) across columns Independent variable (time) down rows 1 mark – Time starts at 0 and is in seconds throughout table (ie not 1 min

20 s)

0.3.3. Drawing scatter graphs

1. Graph plotted with marks allocated as follows:


• Temperature on the x-axis, volume on the y-axis. (1 mark)

• Suitable scales are chosen so that the plotted points cover more than half the graph paper (ie axes do not start at 0). (1 mark)

• Axes labelled with value and unit. (1 mark)

• Points are plotted accurately with a neat pencil cross and within ±1 square. All points plotted accurately 3 marks 4 points plotted accurately 2 marks 3 points plotted accurately 1 mark

2. Error bars are added to each plotted point (except 80 °C, 51.0 cm3) (1 mark)

Anomalous values circled in table not included in error bars (1 mark)

3. Suitable line of best fit drawn (1 mark)

4. As the temperature increases the volume of the gas increases (or suitable similar comparative statement) (1 mark)

Documents

Preparing to Study A Level Chemistry 2020 · This resource “Preparing to Study A Level Chemistry”, is a derivative of “Starters for ten – Transition skills 0.2” by The Royal