1. For which of the following equations is the value of A H equivalent to the bond enthalpy for the carbon-oxygen bond in carbon monoxide?

CO(g) -> C(g) + 0(g)CO(g) * C(s) + O(g)C CO(g) > C(s) + 0 2(g)D CO(g) > C(g) + o 2(g)

2. The bond enthalpy of the bond between nitrogen and oxygen in nitrogen dioxide is 305 kj m ol1. If those of the bonds in the oxygen molecule and the nitrogen molecule are 496 kj mol1 and 944 kj m ol-1 respectively, what will be the enthalpy change for the reaction?

3. Given that the bond enthalpy ot the carbon-oxygen bonds in carbon monoxide and carbon dioxide are 1073 kj m o l '1 and 743 kj m o l '1 respectively, and that of the bond in the oxygen molecule is 496 kj m o l'1, calculate the enthalpy change for the combustion of one mole of carbon monoxide.

4. Given that the enthalpy change for the reaction

N 2(g) + 3Cl2 (g) 2N Cl3(g)-I6VAJ 2 ^ ~is +688 kj m ol ', calculate the bond enthalpy of the

N Cl bond, given that the bond enthalpies in the nitrogen molecule and the chlorine molecule are 944 kj m o l '1 and 242 kj mol-1 respectively.

N 2(g) + 2 0 2(g) -

(^ } +716 kJ m o l '1B +1135 kj m o l '1

^ +1326 kj m o l '1D +1631 kj m o l '1

2 NCL(g)5. Use bond enthalpy data to calculate tne entnalpy

change when cyclopropane reacts with hydrogen to form propane. The actual value found is -159 kj m o l '1. Give reasons why you th ink this differs from the value you have calculated. , 7 , nr v , , , n L - V n f c -[ISon&^entfialpies in kj mol H H 436]

: C- -C 348; CH 412;H L_i i / t w

Consider the halogens (Cl2, Br2, I2) - the bond enthalpies of the halogens given in the table below. Explain the trend in these. Based on the data in the table below, predict a value for the FF bond. Compare this to the literature value, and explain any discrepancy:

ClCl BrBr II

B.E. / kj mo! : 243 193 151

1. Below are four reactions, or series of reactions. W hich o f these would have an overall enthalpy change different from the others?

A NaOH (s) + HQ (aq) N a d (aq) + HjO (1)iJBj NaOH (s) + H20 (1) > NaOH (aq) and

NaOH (aq) + HQ (aq)---- > NaQ (aq) + H^O (1)C NaOH (s) + C 0 2 (g) N aH C 0 3 (s)

and NaHCOj (s) + HC1 (aq) ---- >NaCl (aq) + H 20 (1) + C 0 2 (g)

D HC1 (aq) + MgO (s)------> MgClj (aq) + F^O (1)and MgCl2 (aq) +,NaOH (s) ---->

NaCl (aq) + M g(OH)2 (s)

2. Given the enthalpy changes of the reactions below

2 H 2O z (aq) > 2 H 20 (1) + 0 2 (g)AH = - 2 0 0 kj m o l '1

2 H 2 (g) + 0 2 (g) 2H 20 (1)AH = - 6 0 0 k j m ol 1

what will be the enthalpy change for H 2 (g) + 0 2 (g) > h 2(-)2

a -200 kj mol-1-400 kj m o l'1 C -600 kj mol"'D -800 kj mol-13. Iron and chlorine react directly to form iron(III) chloride, not iron(II) chloride, so that it is not possible to directly measure the enthalpy change for the reaction

Fe (s) + C l2 (g) > FeCl2 (s)

The enthalpy changes for the form ation of iron(III) chloride from the reaction of chlorine with iron and with iron(II) chloride are given below. Use these to calculate the enthalpy change for the reaction of iron with chlorine to form iron(II) chloride.

2 Fe (s) + 3 Cl2 (g) > 2 FeCl3 (s)AH = -8 0 0 k j m ol-1

2 FeCl2 (s) + Cl2 (g) > 2 FeCl3 (s)AH = -1 2 0 k j m ol-1

-286 kj m o l'1 respectively. Use these data to calculate the enthalpy of hydrogenation of ethene (i.e. the reaction of ethene with hydrogen to form ethane).

f5. The decomposition o f calcium carbonate to calcium

oxide and carbon dioxide only "takes place at very high temperatures, m aking the direct m easurement o f the enthalpy change, AH for this reaction difficult. Both calcium carbonate and calcium oxide react readily with dilute hydrochloric acid at room temperature.

a) Describe an experiment to find out LqG-dlti-^ the enthalpy change of these reactions, describing what you would do and stating what m easurements you would make.

b) Which of these two experiments is likely to (_ give the more accurate result? Explain why?4

c) W hat further piece of data would you need ftso that you could use your results to find the enthalpy change for the decomposition of calcium carbonate? /* fi r #U*

d) Given this further information, describe how you would calculate the enthalpy change for

5 - 2_ p io

a) If the pot was made out of aluminium and it weighed 100 g, how m uch heat energy was required to heat the pot (the specific heat capacity of aluminium is 875 J kg"1 K"1)?

b) W hat is the total energy required to heat the pot and water?

c) W hen the water started to boil, the stove weighed 14.5 g less than it had initially. How many moles of butane (C4H )0) were used to heat the pot and water?

d) Use these data to calculate the enthalpy of reaction, in kj mol"1, of butane with air?

e) The accepted value for the enthalpy of combustion of butane is 2874 kj m o l'1. Explain why you think the two values are so different.

4- The enthalpies of combustion of ethene,v ehane and >> r1 hydrogen are -1390 kj m o l'1, -1550 kj m ol1 and

1. W hich one o f the following is not a standard state condition?

A A tem perature of 298 KB A pressure o f 101.3 kPaC All substances in the gaseous stateD Elements present as the standard

allotrope

2. The standard enthalpy change of form ation for hydrogen chloride is the enthalpy change for

A H 2 (g) + Cl2 (g) > 2 HC1 (g)B ViH2 (g) + >/2Cl2 (g) > HC1 (g)C H (g) + Cl (g) > HC1 (g)D H + (g) + C l' (g) HC1 (g)

3. Given the standard enthalpy of formation data:

NaHCOj (s): -948; Na2C 0 3 (s): -1131;C 0 2 (g): -395; H 20 (1): -286; all in kj m ol"1

what is the enthalpy change for the reaction

2 N aH C 03 (s) > Na2C 0 3 (s) + C 0 2 (g) + H 20 (1)

A +84 kj m o r 1B +864 kj mol-1C -864 k] m ol"1D -84 k] mol"1

4. Which one of the following is the reaction for whichthe enthalpy change is equal to the enthalpy change of combustion for ethyne?

A C2H 2 (g) + 2 Vi 0 2 (g) >2 C 0 2 (g) + H 20 (1)

B C2H2 (g) + 1 Vi 0 2 (g) >2 CO (g) + H ,0 (1)

C 2 C2H2 (g) + 5 0 2 (g)4 C 0 2 (g) + 2 H 20 (1)

D C2H 2 (g) + 2 Vi 0 2 (g) >2 C 0 2 (g) + H 20 (g)

5. What value wpuld ydu expect for the enthalpy change of the reaction

C H 3- O H (1) + CO (g) > CH 3 C O O H (1)

Given that & t f comb (CH3OH) = -715 kj mol"1, AH9comb (CO) = -283 kj m ol"1 and A H *comb (CH3COOH) - -876 kj mol"1?

A +161 kj m ol1B +122 k} mol"1C -122 kj mol1D -405 kj mol1

6. W hich one of the following enthalpy terms is not required to calculate the enthalpy of the nitrogen- fluorine bond in nitrogen trifluoride?

A The electron affinity of fluorine.B The fluorine-fluorine bond enthalpy.C The enthalpy of atomisation of nitrogen.D The enthalpy of formation of nitrogen

trifluoride.

7. Given the enthalpies of atomisation of phosphorus and hydrogen (+354 kj m ol1 and +218 kj mol1 respectively) and the phosphorus-hydrogen bond enthalpy (321 kj m ol ), calculate the approximate enthalpy of formation of a hypothetical com poundp h 5.

8. Write balanced equations for the following reactions and use standard enthalpy of formation data to calculate the standard enthalpy change associated with each:

a) Zinc and chlorine reacting to form zincchloride.

b) Hydrogen sulfide and sulfur dioxide reactingto form sulfur and water.

c) Lead(II) nitrate decomposing to lead(II)oxide, nitrogen dioxide and oxygen.

[Standard enthalpy o f formation data, in kj mol : ZnCl2 (s) -416; H,S (g) -21; S 0 2 (g) -297; H 20 ( l) -2 8 6 ; P b (N 0 3)2 (s) -449; PbO (s)-218; N 0 2 (g) +34.]

9. Depending on whether you consider the chlorine to be converted to the element or to hydrogen chloride, it is possible to write two different equations for the combustion of dichlorom ethane (CH2C12). Use enthalpy of formation data to calculate the enthalpy changes of these two reactions. If the experimental value is -578 kj mor1, what conclusions can you draw?

[Standard enthalpy o f form ation data, in kj m ol 1: CH2CL,(l)-121;H C l(g) -92;

|

C O , (g) -395; H20 (1) -286]

10. In the Apollo project, the engines of the lunar m odule mixed methylhydrazine (CH3N H N H 2) and dinitrogen tetroxide (N20 4), which Ignite spontaneously, as fuel for the rocket.

a) Write the m ost probable equation for .the reaction. (It forms com m on simple molecules).

b) Use enthalpy o f form ation data to calculate the enthalpy change for this reaction.

c) W hat factors, apart from the reaction being highly exothermic, would have m ade this combination of fuels suitable for this application?

[Standard enthalpy o f formation data, in kj m ol-1:CH3N H N H 2 (1)+13.0; N 20 4 (g)+9;H20 (g) -244; CO , (g) -395]

11. a) H ow couldyouattem pttom easuretheenthalpychange for the hypothetical isomerisation o f b u ta n -l-o l (C4H9OH) to ethoxyethane (C2H 5OC2H 5) experimentally?

b) Use bond energy data to calculate a value for this enthalpy change.

c) Use enthalpy o f form ation data to calculate a value for this enthalpy change.

d) W hich would you expect to give the best agreement with your experimental value?Why?

[Standard enthalpy of formation data, in kj m ol1:H20 (1) -286; C 0 2 (g) -395; C4H 9OH (1) -327; C2H 5O C2H 5 (1) -280.

Bond energies in kj mol1: CC 346; CH 413;H H 436; C - O 360; O H 464]

12. The enthalpy of combustion data for cyclohexene, cyclohexane and benzene in the gaseous state, in kj m o l'1, are -3752 ,-3924 and -3273.

a) Write balanced equations for the gas phasehydrogenation of cyclohexene to cyclohexane and for benzene to cyclohexane.

b) Use the data given, along with the enthalpy of form ation of water (-286 kj m ol1) to calculate the enthalpy change for these two reactions.

c) Explain the relationship that m ight have been expected between these two values.

d) Explain why this relationship is not in fact found.

/

1. The lattice enthalpy is dependent on two m ain factors, the size of the ions and the charge on the ions. W hich combination of these would lead to the greatest lattice enthalpy?

Size of io n s . .- - V- v. - .:

Charge on ionsA Large LargeB Large SmallC Small LargeD Small Small

2. W hich one of the following quantities is not directly involved in the B orn-H aber cycle?

A Ionisation energyB Lattice enthalpyC ElectronegativityD Enthalpy o f formation

3. W hich one of the following ionic solids would you expect to have the greatest lattice enthalpy?

A RbClB CaSC BaLD LiF

4. Calculate the lattice enthalpy of sodium chloride given the following data:

AH ol(NaCl) = - 4 kj m ol-1

A H hyd{N a+) = -406 k j m o l '1

AHhyd(Cl) = -364 kj m o k 1

A +774 kj mol"1B +766 kj m o l'1C +46 kj mol-1D +38 kj m o k 1

5. W hich one of the following enthalpy terms will always have a different sign to the others?

A Ionisation enthalpyB Enthalpy of hydrationC Lattice enthalpyD Enthalpy of atomisation

6. Use the data beloW, relating to the formation of barium chloride, to calculate a value of the electron affinity of the chlorine atom.

Enthalpy of atomisation of barium + 175 kj mol1

Enthalpy of atomisation of chlorine + 121 kj mol1

First ionisation energy of barium +502 kj mol1

Second ionisation energy of barium +966 kj mol1

Lattice enthalpy of barium chloride +2018 kj mol"1

Enthalpy of formation of barium chloride -860 kj mol1

Enthalpy of atomisation of calcium +193 kj mol1

FF bond enthalpy + 158 kj mol1

First ionisation energy of calcium +590 kj m ol-1

Electron affinity of fluorine -348 kj mol"1

The enthalpy of form ation of CaF2 is -1214 kj mol1. Use this to explain why it is not possible to produce CaF even if two moles of calcium are reacted with one mole of fluorine gas.

8. a) Use the data below to calculate an empirical value for the lattice enthalpy of silver bromide:

Enthalpy of atomisation of silver +285 kj mol1

Enthalpy of atomisation of brom ine+ 112kJm ol1 .

First ionisation energy o f silver+732 kj mol1

Electron affinity of bromine-342 kj mol1

Enthalpy of formation of silver bromide-100 kj mol1

b) If the electrostatic interactions in the lattice are sum m ed to give a theoretical ionisation energy, a value of +758 kj mol1 is found for the lattice enthalpy of silver bromide. Compare this to the value obtained in the first part of the question and com m ent on its significance

7. It would be theoretically possible for calcium to form a fluoride CaF containing Ca+ ions and the F ions in equal numbers. Assuming that the lattice enthalpy of the hypothetical compound is similar to that of NaF (+891 kj mol1), use a B orn- Haber cycle to calculate its enthalpy of formation using the data below.

The theoretical and experimentally determined lattice enthalpies for silver chloride are +833 kj mol1 and +905 kj mol1 respectively. Combine these, with the enthalpy of hydration of the com ponent ions^ H hyd (As +) = -464 kJ mol"! and = ~364kj mol1) to calculate two values for the enthalpy of solution of the compound. Use these to explain the fact that silver chloride is insoluble in water, yet sodium chloride is readily soluble, given that the entropy change for the formation of a solution is similar for both solid salts.

3 5 .Given th e follow ing data:

S (s) + 3 /2 0 2 (g) --> S 0 3(g) A H = -3 9 5 .2 k J2 S 0 2(g) + 0 2 (g) --> 2 S 0 3(g) A H = -1 9 8 .2 k j

Calculate th e A H fo r th e reaction S (s ) + 0 2 (g) > S 0 2(g)

37 . Given th e fo llow ing data:

H z(g) + t 0 2(g) - > H 20 ( l ) A H 0 = -2 8 5 .8 k JN 20 5(g) + H 20 ( l ) ~ > 2 H N 0 3(I) A H 0 = -7 6 .6 k Jt N 2(g) + 3 /2 0 2(g) + i H 2(g) - > H N 0 3 (I) A H 0 = -1 7 4 .1 k J

Calculate th e A H fo r th e reacY\on 2 N 2(g ) + 5 0 2(g) > 2N 20 sJ 39 . Given th e fo llow ing data:

i2 0 3(g) - > 3 0 2(g ) A H = -4 2 7 k J0 2(g) - > 2 0 (g ) A H = + 4 9 5 k J "N O (g ) + 0 3(g ) ~ > N 0 2(g) + 0 2(g) A H = -1 9 9 k J

Calculate th e A H 0 fo r th e reaction N O (g ) + 0 (g ) --> N 0 2 (g)# t . C\ _ . . I I A

41. Given th e follow ing data:

02(g) + H 2(g) > 2 0 H (g ) A H 0 = + 7 7 .9 k J0 2(g) > 2 0 (g ) A H = + 4 9 5 k J 'H 2(g) >2H (g ) A H = + 4 3 5 .9 k J

Calculate th e A H 0 fo r th e reaction 0 (g ) + H (g ) >O H (g)