1. A student carried out an experiment to determine the heat of displacement for the reaction between copper and silver nitrate solution. In this experiment, excess copper powder was added to 100 cm3 of silver nitrate solution 0.5 mol dm3. The heat of displacement in this experiment was 103 kJ mol1.[Specific heat capacity of the solution is 4.2 J g1C1, and the density of the solution is1 g cm3]   (a) What is meant by heat of displacement?   

 [1 mark]

   (b) Besides the data given above, state one other piece of data that is needed to calculate

the heat of displacement.       

[1 mark]   (c) State one precaution that must be taken while carrying out the experiment.       

[1 mark]   (d) (i) State one observation of the experiment.

   

 [1 mark]

(ii) State the reason for the observation in (d)(i).   

 [1 mark]

   (e) Based on the information from this experiment, calculate  (i) the number of moles of silver ions reacted.

 

 

 [1 mark]

(ii) the amount of heat released. 

 

 [1 mark]

(iii)the change in temperature.

 

 

 [1 mark]

   (f) Draw an energy level diagram for the reaction in this experiment. 

  

[1 mark]   (g) The experiment is repeated using 100 cm3 of 1.0 mol dm3 silver nitrate solution and

excess copper powder. Calculate the temperature change in this experiment. 

  

[2 marks]   

2. X is an alcohol, CnH2n+1OH. An experiment was carried out to determine the identity of X by burning a known mass of X in a spirit lamp. The heat produced is used to heat up 190 cm3 of water in a metal tin. It was found that the burning of 0.58 g of X raised the temperature of water by 18.5C.   

(a) State one observation during the experiment that clearly indicated that incomplete combustion of X had occurred.

       

[1 mark]   (b) Table below shows the amount of heat released when 1 mole of three different

alcohols are burnt completely.  Molecular formula

of alcoholRelative molecular

massHeat of combustion

(kJ mol1)Heat of combustion

(kJ g1)

CH3OH 32 728  

C2H5OH 46 1376  

C3H7OH 60 2016  

  Complete table above by calculating the heat released in kJ per gram for each alcohol. 

[2 marks]   (c) (i) Calculate the heat released in this experiment when X is burnt.

  [Specific heat capacity of water = 4.2 J g1C1; density of water = 1 g cm3]

 

 

 [2 marks]

(ii) Calculate the heat released when 1 g of X is burnt.

 

 

 [1 mark]

   (d) From your calculation in (b) and (c)(ii), suggest the identity of X. Explain your

answer.          

[3 marks]

   (e) Write a balanced equation for the reaction that occurred.    

[1 mark]   

3. A pupil carried out an experiment to determine the value of heat of displacement of copper. Zinc powder is added to copper(II) sulphate solution and the mixture is stirred thoroughly.The following data was obtained:

 Initial temperature of copper(II) sulphate solution, 1 = 28.8CHighest temperature of the mixture of products,2 = 45.6C  

(a) Complete the ionic equation for the reaction that occurred.  Zn + Cu2+

 [1 mark]

   (b) In this experiment, excess zinc is added to 64 cm3 of 0.8 mol dm3 copper(II) sulphate

solution.  Given that the specific heat capacity of the solution is 4.2 J g1C1 and the density of

the solution is 1.0 g cm3.  (i) Calculate the change of heat in the experiment.

  Use the formula, H = mc

 

 

 [2 marks]

(ii) Calculate the heat of displacement in the experiment.  The number of moles of copper(II) sulphate that reacted =

 

   Heat of displacement =

 

 

 [2 marks]

   (c) Draw the energy level diagram for reaction. 

  

[2 marks]   (d) It was found that the heat of displacement value in (b)(ii) is not the same as the actual

value.  Suggest one step that must be taken to get a more accurate value.    

[1 mark]   (e) Based on the experiment, what is meant by the heat of displacement?    

[1 mark]   (f) The pupil repeats the experiment, replacing the metal zinc with metal iron and metal

X. The following equations show the reactions and the values of heat of displacement of copper.

  Equation I:  Fe(s) + CuSO4(aq) FeSO4(aq) + Cu(s)     H = 150 kJ mol1

  Equation II:  X(s) + CuSO4(aq) XSO4(aq) + Cu(s)     H = 100 kJ mol1

  Suggest an answer for metal X.    

[1 mark]   

4. (a) (i) State two examples of exothermic reactions.

 [2 marks]

(ii) Draw the energy level diagram for one of the examples in (a)(i).

 [3 marks]

(iii)Explain what is meant by exothermic reaction using the energy level diagram that you have drawn.

 [2 marks]

   (b) Chemical reactions involve the breaking and formation of bonds. Explain how the

breaking and formation of bonds determines whether a reaction is endothermic or exothermic.

 [6 marks]

   (c) Explain why the heat released when one mole of sulphuric acid is neutralised by

excess sodium hydroxide solution is double the heat released when one mole of nitric acid is neutralised by excess sodium hydroxide solution.

 [7 marks]

   5. When aqueous lead(II) nitrate solution and aqueous sodium sulphate solution are mixed,

lead(II) sulphate precipitates. The heat of precipitation of lead(II) sulphate is 50 kJ mol1. (a) (i) What is the colour of lead(II) sulphate?

   

 [1 mark]

(ii) Write a balanced equation for the reaction occurred.   

 [1 mark]

   (b) 35 cm3 of 0.4 mol dm3 lead(II) nitrate solution is added to 35 cm3 of 0.4 mol dm3

sodium sulphate solution.  (i) Name two apparatus that are used in this experiment.

   

 [2 marks]

(ii) Calculate the number of moles of lead(II) ion.

 

 

 [1 mark]

(iii)Calculate the number of moles of sulphate ions.

 

 

 [1 mark]

(iv)Calculate the heat given off in this reaction.

 

 

 [2 marks]

   (c) What is the maximum rise in temperature of the mixture?  [Specific heat capacity of water = 4.2 J g1C1; density of water = 1 g cm3] 

  

[2 marks]   

6. (a) Heat of precipitation of silver chloride is given as = 67.2 kJ mol1. Explain the meaning of this statement.

 [2 marks]

   (b) Write a chemical equation for the formation of silver chloride precipitate and draw its

energy level diagram given that the heat of precipitation, = 67.2 kJ mol1. 

[3 marks]   (c)

 Materials: 0.5 mol dm3 sodium hydroxide solution, 0.5 mol dm3 hydrochloric acidApparatus: Measuring cylinder, thermometer, polystyrene cup

 

  Using the given materials and apparatus, describe an experiment to determine the heat of neutralisation between sodium hydroxide solution and hydrochloric acid.    

 [10 marks]

   (d) Heat released when one mole of sulphuric acid is neutralised by sodium hydroxide

solution is twice the amount of heat released when one mole of hydrochloric acid is neutralised by the same sodium hydroxide solution. Explain why.

 [5 marks]

   7. The diagram below shows the set-up of apparatus to determine the heat of reaction when

copper(II) sulphate pentahydrate, CuSO4.5H2O, dissolves in 100 cm3 of water. The water temperature decreased by 1.7C.

(a) (i) The mass of a test tube together with its content is weighed before the experiment. The empty test tube is then weighed after the experiment.

 

  Calculate the number of moles of copper(II) sulphate hydrate that had dissolved in the water.[Relative formula mass of CuSO4.5H2O = 250]

 

  

[2 marks](ii) Calculate the heat change for this reaction.  [Specific heat capacity of water = 4.2 J g1C1; density of water = 1 g cm3] 

  

[2 marks](iii)Calculate the heat change when 1 mole of CuSO4.5H2O dissolves in 1 dm3 of

water. 

  

[1 mark]   (b) Draw an energy level diagram for the dissolution of CuSO4.5H2O in water.

 

 

 [2 marks]

   (c) Explain the use of a polystyrene cup in this experiment.    

[1 mark]   

(d) Predict the change in temperature if the same amount of CuSO4.5H2O dissolves in 200 cm3 of water.

       

[1 mark]   

8. (a) (i) With your own choice of acids and alkalis, write an equation for the reaction between a strong monoprotic acid and strong alkali., and also a weak acid and a strong alkali.

 [4 marks]

(ii) The heat of neutralisation between a strong monoprotic acid and a strong alkali is different from the heat of neutralisation between a weak monoprotic acid and a strong alkali. Explain the difference.

 [5 marks]

   (b) Using your own choice of materials, describe how you would determine the heat of

displacement in the laboratory. Include the necessary steps of calculation in your answer.      

 [11 marks]

   9. (a) (i) Define heat of neutralisation.

 [1 mark]

(ii) Write four statements about the following thermochemical equation.    HCl(aq) + KOH(aq) KCl(aq) + H2O(l)          H = 57.6 kJ mol1  

 [4 marks]

   (b)

 The heat of neutralisation between a strong acid and a strong alkali is greater than that between a weak acid and a weak alkali.

 

  Describe an experiment to verify the above statement. Your answer should include the following

  • the list of material used• the list of apparatus used• the experimental procedure

•steps showing the calculation of heat of neutralisation (either between strong acid and strong alkali or between weak acid and weak alkali)

 [15 marks]

   10. (a) (i) Give two examples of chemical reactions which are exothermic and two examples

which are endothermic.

 [4 marks]

(ii) Explain exothermic and endothermic reactions in terms of chemical bonds. 

[6 marks]   (b) (i) Define heat of combustion of ethanol, C2H5OH.

 [2 marks]

(ii) An experiment was carried out to determine the heat of combustion of ethanol. A spirit lamp containing a known mass of ethanol is burnt to heat up the water in a copper tin. The table below shows the experimental results.

 

Volume of water in copper tin (cm3)100

Mass of spirit lamp before heating (g) 144.60

Mass of spirit lamp after heating (g) 144.22

Initial temperature of water (C) 28.1

Maximum temperature of water (C) 48.1

  Using the data in the table above, calculate the heat of combustion of ethanol.  [Specific heat capacity of water = 4.2 J g1C1; density of water = 1 g cm3;

Relative atomic mass: H = 1; C = 12; O = 16] 

[6 marks](iii)The actual heat of combustion of ethanol is kJ mol1. Explain the lower

value that was obtained in the experiment. 

[2 marks]   

Answers:  1.  

(a) The heat of displacement is the heat change when one mole of silver is displaced from its solution by copper metal.

(b) The change of the temperature of reaction.(c) Stir the solution throughout the reaction period/ use polystyrene cup.(d) (i) Grey precipitate formed/ the colourless solution turns blue.

(ii) Silver atoms are formed/ copper nitrate formed.(e) (i) Number of moles Ag+ ions

  = number of moles AgNO3 solution used

  =100 0.5

 = 0.050 mole1 000

(ii) 1 mole of Ag+ ions reacts to release 103 kJ of heat.  0.050 mole of Ag+ reacts to release

  =103 0.050

 1

  = 5.150 kJ heat  The heat released in the experiment is 5150 J.(iii)Heat released in the experiment = mc  Temperature change,

  =Heat released

 mc

  =5150 J

 100 g 4.2 J g1C1

  = 12.26 C(f)

(g) Number of moles AgNO3 = 100 1.0

 = 0.10 mole1 000

1 mole of AgNO3 reacts to release 103 kJ of heat. 0.10 mole of AgNO3 reacts to release 10.30 kJ of heat.Temperature change,

10.30  = 24.52 C

100  

  2.  (a) The bottom of the metal tin became black (sooty) / X burnt with a yellow flame.(b) Molecular formula of alcohol Heat of combustion (kJ g1)

CH3OH 22.75

C2H5OH 29.91

C3H7OH 33.60

(c) (i) Heat released when 0.580 g of X is burnt  = heat absorbed by water  = 190 1 4.2 18.5  = 14.763 kJ(ii) Heat released when 1 g of X is burnt

  =14.763

 0.580

  = 25.453 kJ(d) X is C2H5OH. The calculated value of heat of combustion in kJ per g lies between that of

CH3OH (22.750 kJ g1) and C2H5OH (29.913 kJ g1). Heat lost during the experiment has caused the experimental value (25.453 kJ) to be lower than the actual value, therefore, X is ethanol.

(e) C2H5OH + 3O2 2CO2 + 3H2O 

  3.  (a) Zn2+ + Cu(b) (i) H = 64 4.2 16.8 = 4515.84 J

(ii) The number of moles CuSO4 solution that reacts

  =0.80 64

 = 0.051 mole1 000

  Heat of displacement

  =mc

 

number of moles

  =4515.84

 0.051

  = 88545.88 J mole1

  = 88.55 kJ mole1

(c)

(d) Use a plastic cup or add in the zinc powder quickly.(e) The heat released when 1 mole of copper is displaced from its solution.(f) Tin

   4.  

(a) (i) • Burning of magnesium in air to form magnesium oxide

 [1 m]

• Reaction between hydrochloric acid and sodium hydroxide solution to form sodium chloride and water

 [1 m]

(ii)

 [3 m]

(iii)• Exothermic reaction is a reaction that gives out heat to the surroundings.

 [1 m]

• The energy content of the reactants is higher than that of the products.

 [1 m]

(b) • During a reaction, the bonds between the reactants need to be broken.

 [1 m]

• New bonds need to be formed during the formation of the products.

 [1 m]

• Breaking of bonds absorbs energy.

 [1 m]

• Formation of bonds releases energy.

 [1 m]

• If the energy absorbed during bond breaking is more than the energy released during bond formation, the reaction is endothermic.

 [1 m]

• If the energy absorbed during bond breaking is less than the energy released during bond formation, the reaction is exothermic.

 [1 m]

(c) • Nitric acid is a monoprotic acid.

 [1 m]

• 1 mole of nitric acid dissociates to form 1 mole of hydrogen ions.

 [1 m]

• 1 mole of hydroxide ions is required to neutralise 1 mole of hydrogen ions.

 [1 m]

• On the other hand, sulphuric acid is a diprotic acid.

 [1 m]

• 1 mole of sulphuric acid dissociates to form 2 moles of hydrogen ions.

 [1 m]

• 2 moles of hydroxide ions are required to neutralise 2 moles of hydrogen ions.

 [1 m]

• Therefore, the heat released is doubled.

 [1 m]

     5.  

(a) (i) White(ii) Pb(NO3)2 + Na2SO4 PbSO4 + 2NaNO3

(b) (i) Polystyrene cup and thermometer(ii) Number of moles of Pb2+

  =35 0.4

 

1 000  = 0.014 mol(iii)Number of moles of SO4

2

  = 35 0.4  1 000

  = 0.014 mol(iv)Heat released = 0.014 50 = 0.700 kJ

(c) Rise in temperature

=0.700

 (35 + 35) 1

= 2.38C 

  6.  (a) 67.2 kJ of heat energy is released when 1 mole of silver chloride is precipitated from its

aqueous solution.

[2 m](b) AgNO3 + HCl AgCl + HNO3

[1 m]

[2 m](c) • Measure 50.0 cm3 of 0.5 mol dm3 sodium hydroxide solution using a measuring

cylinder and pour it into a polystyrene cup. 

[1 m]• Record its initial temperature as T1. 

[1 m]• Measure 50.0 cm3 of 0.5 mol dm3 hydrochloric acid using a measuring cylinder. 

[1 m]• Record its initial temperature as T2. 

[1 m]• Add the hydrochloric acid to the sodium hydroxide solution in the polystyrene cup. 

[1 m]• Stir the mixture and record the highest temperature reached, T3. 

[1 m]• Temperature change,  

= T3 (T1 T2)

[1 m]2

• Heat change  = mc  = (50 + 50) J   = 0.42 J

 [1 m]

• Number of moles of H+ ions  = number of moles of OHions  = number of moles of H2O 

=0.5(50)

 1000

  = 0.025 mol 

[1 m]• Heat of neutralisation 

=0.42

 kJ mol10.025

 [1 m]

(d) • Hydrochloric acid is monoprotic.

 [1 m]

• 1 mole of hydrochloric acid produces 1 mole of hydrogen ions in water.  HCl H+ + Cl

 [1 m]

• Sulphuric acid is diprotic.

 [1 m]

• 1 mole of sulphuric acid produces 2 moles of hydrogen ions in water.  H2SO4 2H+ + SO4

 [1 m]

• The concentration of hydrogen ions in sulphuric acid is twice the concentration of hydrogen ions in hydrochloric acid.

 [1 m]

     7.  

(a) (i) Mass of CuSO4.5H2O dissolved  = 68.64 40.75  = 27.89 g  Number of mole of CuSO4.5H2O

  =27.89

 250

  = 0.11 mol(ii) Heat released  = 100 4.2 1.7  = 714.0 J or 0.714 kJ(iii)Heat change

  =0.714

 0.11

  = 6.49 kJ(b)

   (c) To minimise heat lost to the surrounding(d) 0.85C

   8.  

(a) (i) HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

 [2 m]

  CH3COOH(aq) + NaOH(aq) CH3COONa(aq) + H2O(l)

 [2 m]

(ii) • The heat of neutralisation is the heat produced when 1 mole of water is formed from the reaction between an acid and an alkali.

 [1 m]

• The heat of neutralisation between a strong acid and a strong alkali is higher than the heat of neutralisation between a weak acid and a strong alkali.

 [1 m]

• A strong acid such as hydrochloric acid dissociates completely in water. 

[1 m]• A weak acid such as ethanoic acid dissociates partially in water. 

[1 m]• Some of the heat given out during neutralisation is absorbed by the molecules of

the week acid to dissociate further. 

[1 m](b) Procedure:

1. 50 cm3 of 2.0 mol dm3 copper(II) sulphate solution is measured.

 [1 m]

2. The copper(II) sulphate solution is poured into a plastic cup.

 [1 m]

3. The initial temperature of the solution is recorded.

 [1 m]

4. Excess zinc powder (more than 1 g) is added quickly to the solution.

 [1 m]

5. The mixture is stirred throughout the experiment.

 [1 m]

6. The highest temperature of the mixture is recorded.

 [1 m]

Results:Initial temperature of solution = t1 CHighest temperature of mixture = t2 CTemperature change = t2 t1 = C

[1 m]Calculations:Number of moles of copper displaced

= 2.0 mol dm3 50

 dm3

1000= 0.1 mol

[1 m]Heat produced= 50 g 4.2 J g1C1 C= a kJ

[1 m]Heat of displacement

= a

 kJ mol10.1

[1 m]CuSO4(aq) + Zn(s) ZnSO4(aq) + Cu(s)

[1 m] 

  9.  

(a) (i) The amount of heat released when 1 mole of water is formed from 1 mole of hydrogen ions in aqueous acid with 1 mole of hydroxide ions in aqueous alkali.

 [1 m]

(ii) • Aqueous hydrochloric acid reacts with aqueous potassium hydroxide to produce aqueous potassium chloride and liquid water.

 [1 m]

• 1 mole of HCl reacts with 1 mole of KOH to form 1 mole of KCl and 1 mole of H2O.

 [1 m]

• 57.6 kJ of heat energy is released when 1 mole of water is formed from the reaction between aqueous hydrochloric acid and aqueous potassium hydroxide.

 [1 m]

• The total energy contents of HCl and KOH is more then that of KCl and H2O. 

[1 m](b) Apparatus:

polystyrene cup, thermometer and measuring cylinder.

[1 m]Materials:hydrochloric acid, aqueous ethanoic acid, sodium hydroxide solution and aqueous ammonia solution.

[1 m]Procedure:1. 50 cm3 of 1.0 mol dm3 sodium hydroxide solution is measured using a measuring

cylinder and poured into a polystyrene cup. 

[1 m]2. 50 cm3 of 1.0 mol dm3 hydrochloric acid solution is measured using a measuring

cylinder and poured into another polystyrene cup. 

[1 m]3. The initial temperature of the acid and alkali solutions are measured after 5 minutes. 

[1 m]4. The acid solution is quickly poured into the alkali solution. The mixture is stirred

continuously using the thermometer. 

[1 m]5. The maximum temperature reached is recorded.

 [1 m]

6. Steps 1 to 5 are repeated using ethanoic acid and aqueous ammonia. 

[1 m]  Results: 

SolutionHydrochloric

acidSodium

hydroxideEthanoic acid Ammonia

Initial temperature (C)

T1 T2 T3 T4

Average temperature (C)

 T1 + T2

 = T5

 2

 T3 + T4

 = T6

 2

Highest temperature

achieved (C)T7 T8

Increase in temperature (C)

T7 T5 = T9 T8 T6 = T10

 [2 m]

  Strong acid and strong alkali  Number of mole of HCl used 

=50 0.1  

1000    = 0.05 mol 

[1 m]  Number of mole of NaOH used 

=50 0.1  

1000    = 0.05 mol 

[1 m]  Heat released in the reaction  = (50 + 50) c T9

  = x J (where c is the specific heat capacity of the mixture) 

[1 m]  The heat released when 1 mole of water is formed 

=x

 0.05

  = 20x J = 0.02x kJ

 [1 m]

  Weak acid and weak alkali  Heat released in the reaction = y J  Heat released when 1 mole of water is formed = 0.02y kJ  0.02x > 0.02y  Heat of neutralisation between strong acid and strong alkali is greater than that

between weak acid and weak alkali. 

[1 m]   

10.  (a) (i) Exothermic reaction

  Neutralisation: HCl + NaOH NaOH + H2O

 [1 m]

  Combustion: C + O2 CO2

 [1 m]

  Endothermic reaction  Acid on carbonate: 2CH3COOH + Na2CO3 2CH3COONa + CO2 + H2O

 [1 m]

  Thermal decomposition: ZnCO3 ZnO + CO2

 [1 m]

(ii) In an endothermic reaction, the total energy absorbed to break chemical bonds in the reactants is more than the total released.In an exothermic reaction, the total energy absorbed to break chemical bonds in the reactants is less than the total energy released.

 [6 m]

(b)(i)

The heat energy released when 1 mole of ethanol is completely burnt in excess oxygen.

 [2 m]

(ii) Heat absorbed by water

 

= 100 (48.1 28.1) 4.2= 8400.00 J

 [1 m]

  Relative molecular mass of ethanol, C2H5O  = 12 2 + 1 5 + 16 + 1  = 46

 [1 m]

  Mass of ethanol burnt  = 144.60 144.22  = 0.38 g

 [1 m]

  Number of mole of ethanol

  =0.38

 46

  = 0.008

 [1 m]

  Heat released when 1 mole of ethanol is burnt

  =8.40

 0.008

  = 1050.00 kJ  The heat of combustion of ethanol is 1050.00 kJ mol1.(iii)Heat lost to the surrounding.

 [1 m]

  Incomplete combustion of ethanol.

 [1 m]