Question

 The rate of a gaseous reaction becomes half when volume of the vessel is doubled. What is the order of reaction ?

Answer 1

Suppose, order of reaction is n and the reaction is A (g) =>Products

 Rate = k[A]n                                                      ...(i)

 When volume is doubled, molar conc. becomes half and rate of reaction gets halved.

Dividing equation (i) by equation (ii),

 (2)1 = (2)ⁿ

 Or n = 1