Which one of the following is a second order reaction ?
`H_2 + Br_2 -> 2HBr`
`NH_4NO_3 -> N_2 + 3H_2O`
`H_2 + Cl_2 stackrel(sunlight)(------>)` 2HCl
`CH_3COOCH_3 + NaOH -> CH_3COONa + H_2O`
Sir how to determine order of a reaction just by seeing the equation ?