The lattice energy of magnesium bromide, MgBr 2 can be calculated using the enthalpy changes shown in the table. Type of enthalpy change Value / kJ mol - 1 first ionisation energy of magnesium + 736 second ionisation energy of magnesium + 1450 first electron affinity of bromine - 325 enthalpy change of formation of MgBr 2 - 524 enthalpy change of atomisation of magnesium + 150 enthalpy change of atomisation of bromine + 112 State the meaning of the term lattice energy.

The energy given out when ions of opposite charges come together to form a crystalline lattice is called the lattice energy, ∆ H latt ⊝ .

The lattice energy of magnesium bromide, MgBr 2 can be calculated using the enthalpy changes shown in the table. Type of enthalpy change Value / kJ mol - 1 first ionisation energy of magnesium + 736 second ionisation energy of magnesium + 1450 first electron affinity of bromine - 325 enthalpy change of formation of MgBr 2 - 524 enthalpy change of atomisation of magnesium + 150 enthalpy change of atomisation of bromine + 112 State the meaning of the term second ionisation energy.

Second ionization energy is the energy required to remove the most loosely bound electron from a 1 + ion of an element. Due to the positive charge on the ion, the electrons are bound more strongly to the nucleus making the second ionization energy of an element always higher than the first.

MEDIUM

AS and A Level

IMPORTANT

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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.

Important Questions on Lattice 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 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

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

Explain why the lattice energy of sodium chloride has a value that is lower than the lattice energy of lithium chloride.

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 3

The table shows the values for all but one of the enthalpy changes relevant to this cycle.

Enthalpy change	Value/ $kJ {mol}^{- 1}$
lattice energy	$- 2327$
enthalpy change of hydration of ${Mg}^{2 +}$ ion	$- 1920$
enthalpy change of hydration of $I^{-}$ ion	$- 314$

Use the values in the table to calculate the value for the enthalpy change of solution of magnesium iodide. (Only give the value without units)

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 4

The lattice energy of magnesium bromide, ${MgBr}_{2}$ can be calculated using the enthalpy changes shown in the table.

Type of enthalpy change	Value / $kJ {mol}^{- 1}$
first ionisation energy of magnesium	$+ 736$
second ionisation energy of magnesium	$+ 1450$
first electron affinity of bromine	$- 325$
enthalpy change of formation of ${MgBr}_{2}$	$- 524$
enthalpy change of atomisation of magnesium	$+ 150$
enthalpy change of atomisation of bromine	$+ 112$

State the meaning of the term lattice 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 4

The lattice energy of magnesium bromide, ${MgBr}_{2}$ can be calculated using the enthalpy changes shown in the table.

Type of enthalpy change	Value / $kJ {mol}^{- 1}$
first ionisation energy of magnesium	$+ 736$
second ionisation energy of magnesium	$+ 1450$
first electron affinity of bromine	$- 325$
enthalpy change of formation of ${MgBr}_{2}$	$- 524$
enthalpy change of atomisation of magnesium	$+ 150$
enthalpy change of atomisation of bromine	$+ 112$

State the meaning of the term second ionisation energy.

Important Questions on Lattice Energy

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