MCQ
A certain weak base has a dissociation constant $2 \times 10^{-5}$. The equilibrium  constant for its neutralisation reaction with strong acid is
  • A
    $2 \times 10^{-5}$
  • B
    $5 \times 10^{10}$
  • C
    $2 \times 10^{-9}$
  • $2 \times 10^{9}$

Answer

Correct option: D.
$2 \times 10^{9}$
d
$\mathrm{K}_{\mathrm{h}}=\frac{\mathrm{k}_{\mathrm{w}}}{\mathrm{k}_{\mathrm{b}}}=\frac{10^{-14}}{2 \times 10^{-5}}=\frac{1}{2} \times 10^{-9}$

$\therefore \mathrm{K}_{\mathrm{N}}=\frac{1}{\mathrm{K}_{\mathrm{h}}}=\frac{1}{\left(1 / 2 \times 10^{-9}\right)}=2 \times 10^{9}$

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