Question

If compound A reacts with $B$ following first order kinetics with rate constant $2.011 \times 10^{-3} s ^{-1}$ The time taken by $A$ (in seconds) to reduce from $7\, g$ to $2\, g$ will be ______ (Nearest Integer) $[\log 5=0.698, \log 7=0.845, \log 2=0.301]$

Answer 1

The correct answer is 623.

at constant volume
t=K2.303​log[A]t​[A]0​​
=2⋅011×10−32.303​log27​
=2⋅011×10−32⋅303×0⋅544​
=622.989
≈623