The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, K 2 O . Type of enthalpy change Value of enthalpy change/ kJ mol - 1 first ionisation energy of potassium + 418 first electron affinity of oxygen - 141 second electron affinity of oxygen + 798 enthalpy change of formation of K 2 O - 361 enthalpy change of atomisation of potassium + 89 enthalpy change of atomisation of oxygen + 249 Copy the incomplete Born-Haber cycle shown below. On the lines A to E of your copy of the Born-Haber cycle, write the correct symbols relating to potassium and oxygen.

The given Born-Haber cycle is completed by giving the correct symbols relating to potassium and oxygen for steps A to E given below: (i) Step A is a result of enthalpy change of atomisation of K . (ii) Step B is a result of enthalpy change of ionisation of K . (iii) Step C is a result of enthalpy change of atomisation of 1 2 O 2 . (iv) Step D is a result of enthalpy change required for the first electron affinity of O . (v) Step E is a result of enthalpy change required for the second electron affinity of O .

The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, K 2 O . Type of enthalpy change Value of enthalpy change/ kJ mol - 1 first ionisation energy of potassium + 418 first electron affinity of oxygen - 141 second electron affinity of oxygen + 798 enthalpy change of formation of K 2 O - 361 enthalpy change of atomisation of potassium + 89 enthalpy change of atomisation of oxygen + 249 Use the data in the table above to calculate the lattice energy of potassium oxide.

The Born-Haber cycle for K 2 O is given below: (i) Step A is a result of enthalpy change of atomisation of K . (ii) Step B is a result of enthalpy change of ionisation of K . (iii) Step C is a result of enthalpy change of atomisation of 1 2 O 2 . (iv) Step D is a result of enthalpy change required for the first electron affinity of O . (v) Step E is a result of enthalpy change required for the second electron affinity of O . ∆ H latt ⊝ = ∆ H f ⊝ - 2 ∆ H at ⊝ [ K ] + 2 IE 1 [ K ] + ∆ H at ⊝ [ O ] + EA 1 [ O ] + EA 2 [ O ] = - 361 - 2 89 + 2 418 + 249 + ( - 141 ) + 418 = - 361 - 1540 = - 1901 kJ mol - 1

The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, K 2 O . Type of enthalpy change Value of enthalpy change/ kJ mol - 1 first ionisation energy of potassium + 418 first electron affinity of oxygen - 141 second electron affinity of oxygen + 798 enthalpy change of formation of K 2 O - 361 enthalpy change of atomisation of potassium + 89 enthalpy change of atomisation of oxygen + 249 Explain why the second electron affinity of oxygen has a positive value.

The addition of first electron to the neutral oxygen atom makes it negatively charged. As the electron is negatively charged, there will be repulsion between the ion and the electron making second electron affinity endothermic, hence the positive value.

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AS and A Level

IMPORTANT

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Draw an enthalpy cycle as an energy level diagram showing the relationship between lattice energy, enthalpy change of solution and enthalpy change of hydration for barium sulfate. $∆ H_{sol}^{⊝} [{BaSO}_{4}]$ is very endothermic.

Important Questions on Lattice Energy

MEDIUM

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>Question>Q 17

Explain why magnesium sulfate is more soluble than barium sulfate by referring to the relative values of the lattice energies and enthalpy changes of hydration.

MEDIUM

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>EXAM-STYLE QUESTIONS>Q 1

The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, $K_{2} O$ .

Type of enthalpy change	Value of enthalpy change/ $kJ {mol}^{- 1}$
first ionisation energy of potassium	$+ 418$
first electron affinity of oxygen	$- 141$
second electron affinity of oxygen	$+ 798$
enthalpy change of formation of $K_{2} O$	$- 361$
enthalpy change of atomisation of potassium	$+ 89$
enthalpy change of atomisation of oxygen	$+ 249$

Copy the incomplete Born-Haber cycle shown below. On the lines A to E of your copy of the Born-Haber cycle, write the correct symbols relating to potassium and oxygen.

Question Image

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>EXAM-STYLE QUESTIONS>Q 1

The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, $K_{2} O$ .

Type of enthalpy change	Value of enthalpy change/ $kJ {mol}^{- 1}$
first ionisation energy of potassium	$+ 418$
first electron affinity of oxygen	$- 141$
second electron affinity of oxygen	$+ 798$
enthalpy change of formation of $K_{2} O$	$- 361$
enthalpy change of atomisation of potassium	$+ 89$
enthalpy change of atomisation of oxygen	$+ 249$

Use the data in the table above to calculate the lattice energy of potassium oxide.

MEDIUM

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>EXAM-STYLE QUESTIONS>Q 1

Describe how, and explain why, the lattice energy of sodium oxide differs from that of potassium sulfide,

K_{2} S

MEDIUM

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>EXAM-STYLE QUESTIONS>Q 1

The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, $K_{2} O$ .

Type of enthalpy change	Value of enthalpy change/ $kJ {mol}^{- 1}$
first ionisation energy of potassium	$+ 418$
first electron affinity of oxygen	$- 141$
second electron affinity of oxygen	$+ 798$
enthalpy change of formation of $K_{2} O$	$- 361$
enthalpy change of atomisation of potassium	$+ 89$
enthalpy change of atomisation of oxygen	$+ 249$

Explain why the second electron affinity of oxygen has a positive value.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>EXAM-STYLE QUESTIONS>Q 2

Define the term first ionisation energy.

EASY

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>EXAM-STYLE QUESTIONS>Q 2

Define the term enthalpy change of atomisation.

MEDIUM

AS and A Level

IMPORTANT

Chemistry for Cambridge International AS & A Level Coursebook with Digital Access (2 Years)>Chapter 19 - Lattice Energy>EXAM-STYLE QUESTIONS>Q 2

Draw and label a Born-Haber cycle to calculate the lattice energy of sodium chloride.

Draw an enthalpy cycle as an energy level diagram showing the relationship between lattice energy, enthalpy change of solution and enthalpy change of hydration for barium sulfate. ∆Hsol⊝ [BaSO4] is very endothermic.

Important Questions on Lattice Energy

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Draw an enthalpy cycle as an energy level diagram showing the relationship between lattice energy, enthalpy change of solution and enthalpy change of hydration for barium sulfate. $∆ H_{sol}^{⊝} [{BaSO}_{4}]$ is very endothermic.