IBChemistry: HLDPTopic Questions15. Energetics/Thermochemistry (HL only)15.1 Energy Cycles

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First teaching 2014

Last exams 2024

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Energy Cycles (DP IB Chemistry: HL)

Topic Questions

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15.1 Energy Cycles

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15.1 Energy Cycles

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1
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What is the correct definition of lattice enthalpy? 

  • Enthalpy change when one mole of solid ionic compound is separated into its ions in their standard state 

  • Enthalpy change when one mole of electrons is removed from one mole of gaseous atoms

  • Enthalpy change when one mole of solid ionic compound is formed from its gaseous ions under standard conditions

  • Enthalpy change when one mole of a compound is formed from its elements

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2
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Which ionic compound has the smallest value for lattice enthalpy?

  • CaBr2

  • NaF

  • MgS

  • MgO

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3
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Which ions hydration enthalpy is the least exothermic?

  • Li+

  • Na+

  • Mg2+

  • Ca2+

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4
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Which steps are endothermic in the Born-Haber cycle for the formation of LiCl?

  1. ½Cl2 (g)  → Cl (g)  
  2. Cl (g) + e- → Cl- (g)
  3. Li (s)  → Li (g)

  • I and II only 

  • I and III only

  • II and III only 

  • I, II and III 

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51 mark

Which equation represents the second electron affinity of nitrogen? 

  • ½N2 (g) + 2e-  → N2- (g) 

  • N (g) + 2e-  → N2- (g) 

  • N2 (g) + 4e-  → 2N2- (g) 

  • N- (g) + e-  → N2- (g) 

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11 mark

Thermodynamic data for the components for magnesium oxide are

Name of enthalpy change

Energy change (kJ mol-1)

Enthalpy of formation of magnesium oxide

-602

Enthalpy of atomisation of magnesium

150

First and second ionisation energy of magnesium 

2188

Enthalpy of atomisation of oxygen

248

First and second electron affinity of oxygen

702

Which of the following is used to calculate the lattice enthalpy of magnesium oxide

  • -602 - 150 - 2188 - 248 + 702

  • -602 - 150 - 2188 - 248 - 702

  • -602 - 150 - 2188 -begin mathsize 14px style 248 over 2 end style- 702

  • -602 - 150 - 2188 - (2 x 248) - 702

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21 mark

Using the information in the table to answer the question 

Enthalpy Change

Value (kJ mol-1)

ΔHӨlatt CaF2

2651

ΔHӨhyd Ca2+

-1616

ΔHӨhyd F-

-504

 

Which of the following is the correct value for the enthalpy change of solution, ΔHӨsol, of calcium fluoride, CaF2?

  • +2651 + [(-1616) + (-504)]

  • +2651 - [(-1616) + (-504)]

  • +2651 + [(-1616) + (-1008)]

  • +2651 - [(-1616) + (-1008)]

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31 mark

Which of the following ionic compounds has the greatest lattice enthalpy?

  • Potassium chloride 

  • Calcium bromide

  • Beryllium oxide

  • Silver bromide

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41 mark

Which of the following changes is not endothermic?

  • K (g) → K+ (g) + e-

  • Cl (g) + e- → Cl - (g)

  • Ca (s) → Ca (g)

  • O- (g) + e- → O2- (g)

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51 mark

Which statements are correct for ionic compounds?

  1. Solubility in water depends on the relative magnitude of the lattice energy compared to the hydration energy
  2. Melting points of ionic compounds increase as the size of the cation increases
  3. The enthalpy of solution for calcium chloride is represented by CaCl2 (s) → CaCl2 (aq)

  • I and II only

  • I and III only

  • II and III only

  • I, II and III

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1
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Which of the following correctly explains the trend in enthalpy of hydration of the metal ions down Group 1?

  • The lone pair of the oxygen atom becomes more available for bonding 

  • The attraction between the ion and the delta negative oxygen atoms in the water decreases down the group

  • The attraction between the ion and the hydrogen ions in water decreases down the group

  • The attraction between the ion and the delta positive hydrogen atoms in water decreases down the group

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2
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Which ionic compound has the most endothermic lattice enthalpy?

  • SrCl2

  • CaO

  • SrO

  • CaCl2

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3
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Which expression represents the first electron affinity of iodine? 

Name of enthalpy change Enthalpy change / kJ mol-1
Enthalpy of atomisation of calcium  +178
1st ionisation energy of calcium  +590
2nd ionisation energy of calcium +1145
Enthalpy of atomisation of iodine +107
Lattice energy of calcium iodide -2074
Enthalpy of formation of calcium iodide  -534

  • -534 - 178 - 590 - 1145 - (2 x 107) - (-2074)

  • -534 - 178 - 590 - 1145 - 107 - (-2074)

  • fraction numerator negative 534 space minus space 178 space minus space 590 space minus space 1145 space minus space left parenthesis 2 space cross times space 107 right parenthesis space minus space left parenthesis negative 2074 right parenthesis over denominator 2 end fraction

  • fraction numerator plus 534 space minus space 178 space minus space 590 space minus space 1145 space minus space left parenthesis 2 space straight x space 107 right parenthesis space plus space 2074 over denominator 2 end fraction

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4
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Which equation represents the correct working to determine the lattice enthalpy of magnesium chloride, ΔHθlatt(MgCl2)? 

Enthalpy change  Representation 
ΔHθsol(MgCl2) x
ΔHθhyd(Mg2+) y
ΔHθhyd(Cl-) z

  • x - (y + z)

  • x + (y + z)

  • x + (y + 2z)

  • x - (y + 2z)

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5
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Which row of the table correctly represents the equations for the lattice enthalpy of substance W2X and the ionisation energy of atom W?

  Lattice enthalpy Ionisation energy 
A. 2W (s) + X2 (g) → W2X W (g) → W+ (g) + e-
B. W2X (s) → 2W+ (g) + X2- (g)  W (g) → W2+ (g) + 2e-
C. W2X (s) → 2W+ (g) + X2- (g)  W (g) → W+ (g) + e-
D. W2X (s) → 2W (g) + X (g)  W (g) → W2+ (g) + 2e-

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