Chemical Reactions/Organic Chemistry

Chapter 4.1

1. What is the Law of Conservation of Mass?

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2. Why must we balance chemical reactions?

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3. Are we allowed to change the subscript numbers in a chemical formula to balance the reaction?

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4. What is a diatomic molecule and which molecules are diatomic?

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5. Balance the following chemical reactions

a) ___FeCl3 + __MgO ---> __Fe2O3 + ___MgCl2

b) __HCl(aq) + ___MnO2(s) ---> ___MnCl2(aq) + __Cl2(g) + __H2O(ℓ)

c) ___P4 + ___O2 ---> ___P2O3

d) ___Fe2O3(s) + __C(s) ---> ___Fe(s) + ___CO2(g)

e) ___Li + ___H3PO4 ---> ___H2 + ___Li3PO4

f) ___ZnS + ___O2 ---> ___ZnO + ___SO2

6. Write the following formula equations and balance them.

a) Propanol (C3H7OH) reacts with excess oxygen to form carbon dioxide and water.

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b) Butane (C4H10) reacts with limited oxygen to form carbon monoxide and water.

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c) Octane (C8H18) reacts with very limited oxygen to form charcoal and water.

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d) Acetylene (C2H2) reacts with excess oxygen to form carbon dioxide and water.

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e) Acetone (C3H6O) reacts with oxygen to form carbon dioxide and water.

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f) Toluene (C6H5CH3) reacts with oxygen to form carbon dioxide and water.

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7. Identify if the following reactions are balanced and obey the Law of Conservation of Mass.

State whether they are balanced and if they are not balanced then fix them so that they are

balanced.

a) S8 + 6O2 --> 8SO3

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b) 4Fe + 3O2 + 2H2O --> 3Fe2O3 + H2O

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c) 3H2 + 2O2 3H2O

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8. Write balanced chemical equations to represent each of these chemical reactions.

a) The Haber process is an important chemical reaction where gaseous ammonia is produced by

reacting hydrogen gas with nitrogen gas.

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b) Magnesium hydroxide is an ingredient in common antacids. It reacts with dilute hydrochloric acid in

the stomach to produce a solution of magnesium chloride and water.

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c) Zinc metal reacts with dilute sulfuric acid to form dilute zinc sulfate and hydrogen gas.

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Chapter 4.2 Reactivity

9. Explain what a spontaneous reaction is and give a few examples of spontaneous reactions.

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10. What is an ionic equation? What are spectator ions in an ionic equation?

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11. Use the reaction between Tin and hydrochloric acid to and write the balance formula equation, the

ionic equation and net ionic equations plus identify the spectator ion.

a. Formula Eq_______________________________________________________________

b. Ionic Eq:_______________________________________________________________________

c. Spectator ion____________

d. Net ionic equation________________________________________________________________

e. State any observations you would expect to see during this reaction.

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12. Explain the difference between Single displacement versus double displacement or replacement

reactions. Give examples of each.

i. Single displacement general formula.

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ii. Single displacement reaction example

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iii. Double displacement general formula.

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iv. Double displacement reaction example

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Acid Metal Reactions and Single Displacement Reactions

13. Using the activity series, predict and balance the formula equation for the following single displacement

reactions. Use abbreviations to indicate the appropriate phase of reactants and products. For those that do

not react, write no reaction.

a. A piece of calcium is dropped into a container of water.

b. An aluminum strip is immersed in a solution of nitric acid.

c. Zinc pellets are added to a sulfuric acid solution.

d. Magnesium turnings are added to a solution of lead (II) acetate.

e. Calcium metal is added to a solution of nitric acid.

f. A pea-sized piece of lithium is added to hydrochloric acid.

14. Write the net ionic equation and observations for the following single displacement reactions.

a) Calcium metal with water

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Observations

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b) Magnesium with phosphoric acid

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Observations

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c) Nickel and nitric acid

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Observations

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d) Iron and oxygen

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Observations

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Watch Videos:

Exothermic Reaction: http://www.youtube.com/watch?v=6zg1it_fVlk Endothermic Reaction: http://www.youtube.com/watch?v=5RJLvQXce4A

1. Describe what an exothermic reaction is.

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Give one example of an exothermic reaction:

2. Describe what an endothermic reaction is.

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Give one example of an endothermic reaction:

3. What is the Law of Conservation of Energy?

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4. Taking into consideration the Law of Conservation of Energy, where does the heat come from during an

exothermic reaction?

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5. When continually adding heat to enable an endothermic reaction to occur, where does all the heat energy

go if it is not destroyed?

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6. Bonds hold _____________________energy.

7. Temperature is a measure of _____________________energy.

8. The more energy a bond holds the less____________________that bond is.

9. During an exothermic reaction, high energy bonds in the reactants break and energy is

___________________. The bonds in the products will have ___________ energy stored in

them when compared to the bonds in the products. The products will be ____________stable

than the bonds in the reactants.

10. a) Write the formula equation for the burning of methane which you know is an exothermic reaction

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b) Draw a diagram that shows what is described in question 9.

Use the reaction of burning methane in an oxygen atmosphere.

Potential

Energy

(kJ)

11. During an endothermic reaction, ________ energy bonds in the reactants break and energy is

___________________as higher energy bonds in the products are formed. The products will

be ____________stable than the bonds in the reactants.

12. Draw a diagram that shows what is described in question 11. Use the reaction of epson salts (MgSO4)

dissolving in water.

Potential

Energy

(kJ)

1. The energy diagram shown below is for the decomposition of hydrogen chloride.

2 HCl (g) H2 (g) + Cl2 (g) HCl

a) Is this reaction exothermic or endothermic?________________

b) Is heat energy is ________________during this reaction. H2 (g) + Cl2 (g)

c) The surrounding air will become_________________.

2. Complete the gaps in the two paragraphs, selecting from the words in the word bank below.

Word Bank:

released absorbed increased decreased produced

kinetic potential greater less

For an endothermic reation, the potential energy stored in the bonds of the reactants is _____________________

than the potential energy of the products in the reacting system. Heat energy is ________________ from the

surroundings and changed into ________________________energy during the reaction. The temperature of the

surroundings will ______________________.

For an exothermic reation, the potential energy stored in the bonds of the reactants is _____________________

than the potential energy of the products in the reacting system. Heat energy is ________________ by the

system and the _______________energy of the molecules in the surroundings will _______________. The

temperature of the surroundings will ______________________.

1. Explain what Enthalpy is.

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2. Explain what heat of reaction is.

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3. Explain what an Enthaply change is and what symbol is used Enthalpy change.

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Enthalpy (H) & enthalpy change (H )

Enthalpy is the “heat content” of a substance.

or - the total KE & PE of a substance at const. pressure.

Chemists are interested in enthalpy changes (H ) because it can be a source of energy or a way to cool a

system.

How Equations can be written to identify whether they are exo or endothermic.

A) Using ΔH

H2 + S ---> H2S H = - 20 KJ ( - H means exothermic)

6C + 3H2 ---> C6H6 H = + 83 KJ ( + H means endothermic)

B) Thermochemical equations:

The “heat term” can be placed right into the equation. No “H” is shown beside the equation!

When the “heat term” is shown on left side of arrow - endothermic (“it uses up heat like a reactant”)

CH3OH + 201KJ C(s) + 2H2(g) + ½ O2(g) ∆H is________

When the “heat term” is shown on right side of arrow -exothermic ( “it gives off heat like a product”)

S(g) + O2(g) ---> SO2(g) + 296 kJ ∆H is________

Enthalpy (H) H + H

H 2

H

Reaction Proceeds

Heat is released to surroundings.

Exothermic H is negative (-)

Enthalpy (H)

O + O

H

Reaction Proceeds

Heat is absorbed from the surroundings.

Endothermic H is positive (+) 2 O

shown

beside

Practice:

1. Write the following reaction in ΔH notation. 2. Write the following reaction in Standard Notation.

A + B + 200 kJ → C H2 + I2 → 2 HI ΔH = -250 kJ

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3. Write in Standard Notation.

2NI3 + 3BaCl2 → 2NCl3 + 3BaI2 ΔH = 175 kJ

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4. Write in ΔH notation.

2AlBr3 + 3BaF2 → 2AlF3 + 3BaBr2 + 276 kJ

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Problems 1) The thermochemical equation for respiration is:

C6H12O6 + O2 CO2 + H2O + 2803 kJ

a) Rewrite the equation in ΔH notation.

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b) Is the reaction endo or exothermic?___________________

Organic Chemistry 1) Write the balanced chemical equation for the combustion of ethane in excess oxygen.

[3 marks]

2) Draw the structure of 2,3-dibromobut-2-ene. [1 mark]

3) Draw all three structural isomers of pentane. [3 mark]

4) Name the following molecules using the IUPAC naming conventions. [4 marks]

a)

b)

Answer: .

Answer: .

c)

d)

5) Write the balanced equation for the complete combustion of benzene. [3 marks]

6) Explain how bromine water can be used to determine if a liquid is an alkane or an alkene. Include an

explanation of what occurs and why. [4 marks]

Answer: .

Answer: .

7) Chlorine (Cl2) is reacted with three liquids – hexane, hex-2-ene and benzene. [3 marks]

a) Draw the structural formula for the products made when chlorine is reacted with hexane in the

presence of UV light.

b) Draw the structural formula for the product made when chlorine is reacted with

hex-2-ene.

c) Draw the structural formula for the products made when chlorine is reacted with benzene in the

presence of an aluminium chloride (AlCl3) catalyst.

8) List the general molecular formulas for non-cyclic alkanes, non-cyclic alkenes and benzene.

[3 marks]

Non-cyclic alkane: .

Non-cyclic alkene: .

Benzene: .

9) Explain why alkanes and alkenes have similar physical properties but have very different chemical

properties. [3 marks]

10) Describe some common uses for three different hydrocarbons and include a brief explanation of which

chemical property makes this use possible. [3 marks]

11) Write the structural formula for the product formed with hept-2-ene is mixed with hydrogen gas in the

presence of a catalyst. . [1 mark]

12) Explain why benzene is extremely stable. Include a diagram in your explanation. [2 marks]