For a first order reaction, (A) -> product the concentration of A changes from 0.1 M to 0.025 M in40 min. The rate of reaction when the concentration of A is 0.01 M is

For the first order reaction, 2.303 0.1 log 40 0.025 2.303 2.303 log 4 log 2 20 20 2.303 (0.301) 20 K K K So the value of K = 0.0347 Rate = [ ] K A Put the value of K in the above equation: Rate = 2 4 1 0.0347 10 3.47 10 min M x x Hence the correct answer is option (b)