The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, ${\mathrm{K}}_2\mathrm{O}$.

Type of enthalpy change	Value of enthalpy change/$\mathrm{kJ} {\mathrm{mol}}^{-1}$
first ionisation energy of potassium	$+418$
first electron affinity of oxygen	$-141$
second electron affinity of oxygen	$+798$
enthalpy change of formation of ${\mathrm{K}}_2\mathrm{O}$	$-361$
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 table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, ${\mathrm{K}}_2\mathrm{O}$.

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

The table shows the enthalpy changes needed to calculate the lattice energy of potassium oxide, ${\mathrm{K}}_2\mathrm{O}$.

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

Define the term first ionisation energy.

Define the term enthalpy change of atomisation.

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

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

Draw an energy cycle to show the dissolving of magnesium iodide in water.