WAEC Chemistry 2019 Theory — Question 23

Model answer

To prepare hydrogen from water gas, the water gas (a mixture of CO and H2) is mixed with excess steam and passed over an iron oxide catalyst at 400–500°C. This produces more hydrogen while the carbon(II) oxide in the water gas is oxidized to carbon(IV) oxide: CO + H2 + H2O →(catalyst)→ CO2 + 2H2 The carbon(IV) oxide formed is removed by dissolving it in water under pressure (about 30 atmospheres); any unreacted CO is absorbed in an ammoniacal solution of copper(I) methanoate, leaving pure hydrogen gas.