Q.

The rate constant for a first order reaction is 4.606×10-3 s-1. The time required to reduce 2.0 g of the reactant to 0.2 g is              [2020]

1 100 s  
2 200 s  
3 500 s  
4 1000 s    

Ans.

(3)

For a first order reaction,  

k=2.303tlog[R]0[R]

t=2.3034.606×10-3s-1log(20.2)=2.303×1034.606=500 s