JEE MAIN - Chemistry (2022 - 25th July Morning Shift - No. 4)
$$20 \mathrm{~mL}$$ of $$0.1\, \mathrm{M} \,\mathrm{NH}_{4} \mathrm{OH}$$ is mixed with $$40 \mathrm{~mL}$$ of $$0.05 \mathrm{M} \mathrm{HCl}$$. The $$\mathrm{pH}$$ of the mixture is nearest to :
(Given : $$\mathrm{K}_{\mathrm{b}}\left(\mathrm{NH}_{4} \mathrm{OH}\right)=1 \times 10^{-5}, \log 2=0.30, \log 3=0.48, \log 5=0.69, \log 7=0.84, \log 11= 1.04)$$
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Explanation
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$\left[\mathrm{NH}_4^{+}\right]=\frac{2 \mathrm{mmole}}{60 \mathrm{ml}}=\frac{1}{30} \mathrm{M}$
$\mathrm{pH}=\frac{\mathrm{pK}_{\mathrm{w}}-\mathrm{pK}_{\mathrm{b}}-\log \mathrm{C}}{2}=\frac{14-5+1.48}{2}=5.24$
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