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 $7g$ to $2g$ will be ______ (Nearest Integer)
$[\log 5=0.698,\log 7=0.845,\log 2=0.301]$

Answer 1

Answer: 623

at constant volume
$t=\frac{2.303}{K}\log \frac{[A{]}_0}{[A{]}_t}$
$=\frac{2.303}{2\cdot 011\times 10^{-3}}\log \frac{7}{2}$
$=\frac{2\cdot 303\times 0\cdot 544}{2\cdot 011\times 10^{-3}}$
$=622.989$
$\approx 623$