Calculate the energy change for the reaction K (g) + Br (g) → K + (g) + Br - (g) given the following ionization energy (IE) and electron affinity (EA) values IE EA K: 419 kJ/mol 48 kJ/mol Br: 1140 kJ/mol 324 kJ/mol

95 KJ/mol

Explanation:

Ionization energy is the energy required to remove an electron from a gaseous element. This involves breaking of bonds as electron is lost hence its endothermic. and this energy is positive

Electron affinity is the energy necessary to add an electron to a gaseous element. This involves building of bonds as electron is gained. Hence reaction is exothermic and energy involved is negative.

From the reaction below

K (g) + Br (g) → K + (g) + Br - (g)

we shall consider the reactants;

K (g) → K + (g)

potassium looses an electron to become positively charged. hence this reaction involves ionization energy. IE (K) = 419kJ/mol

Br (g) → Br - (g)

Bromine gains an electron to become negatively charged. this involves formation of bond and this releases heat (exothermic). The energy for this comes as electron affinity. EA (Br) = - 324KJ/mol

Change is energy is thus calculated with the following formula;

ΔE = Ionization energy + Electron affinity

ΔE = IE (k) + EA (Br)

ΔE = 419 + (-324)

ΔE = 419-324

ΔE = 95KJ/mol