A first order reaction has a specific reaction rate of 10– 2 sec–1. How much time will it take for 20g of the reactant to reduce to 5 g? (NEET 2017)

Half-life for a first order reaction, 1/2 0.693 t k So, 1/2 2 0.693sec 10 t Also, for the reduction of 20 g or reactant to 5 g, two half lives will be required. For 20 g of the reactant to reduce to 5g, time taken, 2 0.693 2 sec 138.6sec 10 t x .