Q.

A first order reaction has a rate constant of 2.303×10-3 s-1. The time required for 40 g of this reactant to reduce to 10 g will be

[Given that log10 2 = 0.3010]                           [2019]

1 230.3 s  
2 301 s  
3 2000 s  
4 602 s  

Ans.

(4)

For a first order reaction, k=2.303tlog[A]0[A]t

2.303×10-3=2.303tlog4010

t=110-3log22=210-3log2=210-3×0.3010=602 s