Question

Why is Carbon monoxide passed through washer bottle containing caustic potash solution?​

Answer 1

This is done to remove the impurity Carbon Dioxide gas.

Caustic Potash or Concentrated Potassium Hydroxide solution is a very good absorber of Carbon dioxide gas, hence on bubbling impure Carbon Monoxide in it, Carbon Dioxide gas is removed and pure Carbon Monoxide is obtained.

Carbon Dioxide Reacts with KOH as follows:

2KOH + CO2 ---------> K2CO3 + H2O