Question

A drop $\left(0.05\,mL\right)$ of a solution contains $3.0\times 10^{- 6}$ moles of $H^{+}$ Ions. If the rate constant of disappearance of $H^{+}$ ion is $1.0\times 10^{7} \,mol\,litre^{- 1}sec^{- 1},$ the time taken for $H^{+}$ ions in the drop to disappear is $p\times 10^{- q}.$ Calculate the value of $q-p$ .
Give the nearest integer as the answer.

Answer 1

Concentration of drop $=\frac{\text { mole }}{\text { volume in mL }} \times 1000$
$=\frac{3 \times 10^{-6}}{0.05} \times 1000=0.06$ mole litre ${ }^{-1}$
Rate of disappearence $=\frac{\text { conc.change }}{\text { time }} 1 \times 10^{7}= \frac{0.06}{\text { time }}$
Time $=6 \times 10^{-9}$ Sec So, $q-p=3$