1. Which combination of ionic charge and ionic radius give the largest lattice enthalpy for an ionic compound?
Ionic charge
high
high
low
low
A.
B.
C.
D.
2.
3.
4.
Ionic radius
large
small
small
large
Which reaction has a positive entropy change, ∆Sο?
A.
H2O(g) → H2O(l)
C.
2SO2(g) + O2(g) → 2SO3(g)
B.
CaCO3(s) → CaO(s)+ CO2(g)
D.
N2(g) + 3H2(g) → 2NH3(g)
Some chlorine gas is placed in a flask of fixed volume at room temperature. Which change will cause a
decrease in entropy?
A.
adding a small amount of hydrogen
C.
adding a small amount of chlorine
B.
cooling the flask
D.
exposing the flask to sunlight
The lattice enthalpy values for lithium fluoride and calcium fluoride are shown below.
LiF(s)
CaF2(s)
∆Hο = +1022 kJ mol−1
∆Hο = +2602 kJ mol−1
Which of the following statements help(s) to explain why the value for lithium fluoride is less than that for
calcium fluoride?
5.
I.
The ionic radius of lithium is less than that of calcium.
II.
The ionic charge of lithium is less than that of calcium.
A.
I only
C.
II only
B.
I and II
D.
Neither I nor II
Which reaction occurs with the largest increase in entropy?
A.
Pb(NO3)2(s) + 2KI(s) → PbI2(s) + 2KNO3(s)
B.
CaCO3(s) → CaO(s) + CO2(g)
C.
3H2(g) + N2(g) → 2NH3(g)
D.
H2(g) + I2(g) → 2HI(g)
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6.
What is ∆H for the reaction below in kJ?
CS2(g) + 3O2(g)  CO2(g) + 2SO2(g)
[∆Hf / kJ mol–1: CS2(g) 110, CO2(g) – 390, SO2(g) – 290]
A.
−570
C.
−790
B.
−860
D.
−1080
7.
Write all of the reactions for the formation of solid potassium oxide, K2O(s), from its elements in
their standard states. The lattice energy of K2O(s) is 2238 kJ/mol. Use these data along
with data in Appendix C and Figure 7.10 to calculate the “second electron affinity” of
oxygen corresponding to the reaction O-(g) + e-  O2-(g).
8.
The standard enthalpy change of formation of Al2O3(s) is −1669 kJ mol−1 and the standard enthalpy change
of formation of Fe2O3(s) is −822 kJ mol−1.
(i)
Use these values to calculate ∆Hο for the following reaction.
Fe2O3(s) + 2Al(s) → 2Fe(s) + Al2O3(s)
State whether the reaction is exothermic or endothermic.
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(ii) Draw an enthalpy level diagram to represent this reaction. State the conditions under which
standard enthalpy changes are measured.
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(iii)
Estimate, without doing a calculation, the magnitude of the entropy change for this reaction. Explain
your answer.
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9.
Define the term standard enthalpy of formation, and write the equation for the standard enthalpy of
formation of ethanol, C2H5OH(l).
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10.
C2H6(g) ↔ C2H2(g) + 2 H2(g)
Substance
C2H2(g)
H2(g)
C2H6(g)
S°(J mol-1 K-1)
200.9
130.7
--------
H°f (kJ mol-1)
226.7
0
-84.7
If the value of the standard entropy change, S°, for the reaction is 232.7 J mol-1 K-1, calculate the standard
molar entropy, S°, of C2H6 gas.
11. Using the standard enthalpies of combustion, Table 12, calculate the determine the enthalpy of reaction
of octane (C8H18) from its elements at standard conditions.
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