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1.
Which statement about bonding is correct?
A.
Bond breaking is endothermic and requires energy.
B.
Bond breaking is endothermic and releases energy.
C.
Bond making is exothermic and requires energy.
D.
Bond making is endothermic and releases energy.
(Total 1 mark)
2.
Methanol is made in large quantities as it is used in the production of polymers and in fuels.
The enthalpy of combustion of methanol can be determined theoretically or experimentally.
CH3OH(l) + 1
(a)
1
O2(g) → CO2(g) + 2H2O(g)
2
Using the information from Table 10 of the Data Booklet, determine the theoretical
enthalpy of combustion of methanol.
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(3)
IB Questionbank Chemistry
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(b)
The enthalpy of combustion of methanol can also be determined experimentally in a
school laboratory. A burner containing methanol was weighed and used to heat water in a
test tube as illustrated below.
The following data were collected.
(i)
Initial mass of burner and methanol / g
80.557
Final mass of burner and methanol / g
80.034
Mass of water in test tube / g
20.000
Initial temperature of water / °C
21.5
Final temperature of water / °C
26.4
Calculate the amount, in mol, of methanol burned.
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(2)
IB Questionbank Chemistry
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(ii)
Calculate the heat absorbed, in kJ, by the water.
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(3)
(iii)
Determine the enthalpy change, in kJ mol–1, for the combustion of 1 mole of
methanol.
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(2)
(c)
The Data Booklet value for the enthalpy of combustion of methanol is –726 kJ mol–1.
Suggest why this value differs from the values calculated in parts (a) and (b).
(i)
Part (a)
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(1)
(ii)
Part (b)
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(1)
(Total 12 marks)
IB Questionbank Chemistry
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3.
Which processes have a negative enthalpy change?
I.
2CH3OH(l) + 3O2(g) → 2CO2(g) + 4H2O(l)
II.
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
III.
H2O(g) → H2O(l)
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II and III
(Total 1 mark)
4.
Which equation represents the bond enthalpy for the H–Br bond in hydrogen bromide?
A.
HBr(g) → H(g) + Br(g)
B.
HBr(g) → H(g) + Br(l)
C.
HBr(g) → H(g) +
1
Br2(1)
2
D.
HBr(g) → H(g) +
1
Br2(g)
2
(Total 1 mark)
5.
Propane can be formed by the hydrogenation of propene.
CH3CH=CH2(g) + H2(g) → CH3CH2CH3(g)
(i)
State the conditions necessary for the hydrogenation reaction to occur.
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(2)
IB Questionbank Chemistry
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(ii)
Enthalpy changes can be determined using average bond enthalpies. Define the term
average bond enthalpy.
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(2)
(iii)
Determine a value for the hydrogenation of propene using information from Table 10 of
the Data Booklet.
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(2)
(iv)
Explain why the enthalpy of hydrogenation of propene is an exothermic process.
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(1)
(Total 7 marks)
6.
Hydrazine is a valuable rocket fuel.
The equation for the reaction between hydrazine and oxygen is given below.
N2H4(g) + O2(g) → N2(g) + 2H2O(g)
Use the bond enthalpy values from Table 10 of the Data Booklet to determine the enthalpy
change for this reaction.
(Total 3 marks)
IB Questionbank Chemistry
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7.
A pure aluminium block with a mass of 10 g is heated so that its temperature increases from
20 °C to 50 °C . The specific heat capacity of aluminium is 8.99 × 10–1 J g–1 K–1. Which
expression gives the heat energy change in kJ?
A.
10 × 8.99 × 10–1 × 303
B.
10 × 8.99 × 10–1 × 30
C.
10  8.99  10 1  303
1000
D.
10  8.99  10 1  30
1000
(Total 1 mark)
8.
Which combination is correct for a chemical reaction that absorbs heat from the surroundings?
Type of reaction
ΔH at constant pressure
A.
Exothermic
Positive
B.
Exothermic
Negative
C.
Endothermic
Positive
D.
Endothermic
Negative
(Total 1 mark)
9.
When hydrogen peroxide decomposes, the temperature of the reaction mixture increases.
2H2O2(aq) → O2(g) + 2H2O(l)
What are the signs of ∆H, ∆S and ∆G for this reaction?
∆H
∆S
∆G
A.
–
–
–
B.
–
+
–
C.
+
+
–
D.
–
+
+
(Total 1 mark)
IB Questionbank Chemistry
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10.
Which equation corresponds to the lattice enthalpy for silver iodide, AgI?
A.
AgI(s) → Ag(s) + I(g)
B.
AgI(s) → Ag(s) +
C.
AgI(s) → Ag+(aq) + I–(aq)
D.
AgI(s) → Ag+(g) + I–(g)
1
I2(g)
2
(Total 1 mark)
11.
Some words used in chemistry can have a specific meaning which is different to their meaning
in everyday English.
State what the term spontaneous means when used in a chemistry context.
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(Total 1 mark)
12.
Propene can be hydrogenated in the presence of a nickel catalyst to form propane.
Use the data below to answer the questions that follow.
(i)
∆HOf / kJ mol–1
SO/ J K–1 mol–1
0
+ 131
C3H8(g)
– 104
+ 270
C3H6(g)
+ 20.4
+ 267
Compound
Formula
hydrogen
H2(g)
propane
propene
Outline why the value for the standard enthalpy change of formation of hydrogen is zero.
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(1)
IB Questionbank Chemistry
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(ii)
Calculate the standard enthalpy change for the hydrogenation of propene.
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(2)
(iii)
Calculate the standard entropy change for the hydrogenation of propene.
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(2)
(iv)
Determine the value of ∆GO for the hydrogenation of propene at 298 K.
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(2)
(v)
At 298 K the hydrogenation of propene is a spontaneous process. Determine the
temperature above which propane will spontaneously decompose into propene and
hydrogen.
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(2)
(Total 9 marks)
IB Questionbank Chemistry
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13.
What is the standard free energy change, ∆GO, in kJ, for the following reaction?
C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(g)
Compound
∆GfO / kJ mol–1
C2H5OH(l)
–175
CO2(g)
–394
H2O(g)
–229
O2(g)
A.
–1650
B.
–1300
C.
– 448
D.
+1300
0
(Total 1 mark)
14.
Which reaction has the most negative change in entropy?
A.
2SO2(g) + O2(g) → 2SO3(g)
B.
NH4Cl(s) → NH3(g) + HCl(g)
C.
PbCl2(s) → Pb2+(aq) + 2Cl–(aq)
D.
C(s) + O2(g) → CO2(g)
(Total 1 mark)
15.
Which step(s) is/are endothermic in the Born-Haber cycle for the formation of LiCl?
A.
½Cl2(g) → Cl(g) and Li(s) → Li(g)
B.
Cl(g) + e– → Cl–(g) and Li(g) → Li+(g) + e–
C.
Li+(g) + Cl–(g) → LiCl(s)
D.
½Cl2(g) → Cl(g) and Cl(g) + e– → Cl–(g)
(Total 1 mark)
16.
The lattice enthalpy of magnesium chloride can be calculated from the Born-Haber cycle shown
IB Questionbank Chemistry
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below.
(i)
Identify the enthalpy changes labelled by I and V in the cycle.
(2)
(ii)
Use the ionization energies given in the cycle above and further data from the Data
Booklet to calculate a value for the lattice enthalpy of magnesium chloride.
(4)
(iii)
The theoretically calculated value for the lattice enthalpy of magnesium chloride is
+2326 kJ. Explain the difference between the theoretically calculated value and the
experimental value.
(2)
(iv)
The experimental lattice enthalpy of magnesium oxide is given in Table 13 of the Data
Booklet. Explain why magnesium oxide has a higher lattice enthalpy than magnesium
chloride.
(2)
(Total 10 marks)
17.
Consider the following Born-Haber cycle:
IB Questionbank Chemistry
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The magnitudes for each of the enthalpy changes (a to e) are given in kJ mol–1 but their signs
(+ or –) have been omitted.
(i)
State the names for the enthalpy changes c and d.
(2)
(ii)
Deduce which two of the enthalpy changes a to e have negative signs.
(1)
(iii)
Determine the value for the enthalpy of formation of potassium bromide.
(2)
(iv)
Explain why the quantitative value for the lattice enthalpy of calcium bromide is larger
than the value for the lattice enthalpy of potassium bromide.
(2)
(Total 7 marks)
IB Questionbank Chemistry
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18.
Which ionic compound has the most endothermic lattice enthalpy?
A.
NaCl
B.
KCl
C.
NaF
D.
KF
(Total 1 mark)
19.
What are the signs of ∆Hο and ∆Sο for a reaction that is non-spontaneous at low temperature but
spontaneous at high temperature?
Hο
Sο
A.
–
–
B.
+
–
C.
–
+
D.
+
+
(Total 1 mark)
20.
(i)
Define the terms lattice enthalpy and electron affinity.
(2)
(ii)
Use the data in the following table and from the data booklet to construct the Born-Haber
cycle for sodium chloride, NaCl, and determine the lattice enthalpy of NaCl(s).
Na(s) +
1
Cl2(g) → NaCl(g)
2
Na(s) → Na(g)
∆Hο = –411 kJ mol–1
∆Hο = +108 kJ mol–1
(4)
(iii)
Describe the structure of sodium chloride.
(2)
(Total 8 marks)
IB Questionbank Chemistry
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