Assertion: Yellow coloured aqueous solution of sodium chromate changes to orange red when CO₂ under pressure is passed.

Reason: Orange colour of solution is due to conversion of chromate ions into dichromate ions.

Assertion and Reason both are correct statements and reason is the correct explanation for assertion.

CO₂ form acidic solution.

2CrO₄^2- + 2H⁺ → Cr₂O₇^2- + H₂O

(yellow)           (Orange red)