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Q.
If the $pH$ of a mixture of $10\, mL$ of $0.1 \,M\, NH_4OH$ and
$10\, mL$ of $1\, M \,NH_4Cl$ solution is $8$, the $pK_b$ value of $NH_4OH$ is the n closest to
KVPYKVPY 2009Equilibrium
Solution:
Given, $pH$ of a mixture = $8$
Concentration of $NH_4OH = 0.1\, M$
Concentration of $NH_4 Cl = 1 \,M$
$pOH = 14 - pH$
$pOH=14-8=6$
$\therefore PK_{b}=pOH+\log\frac{\left[NH_{4}Cl\right]}{\left[NH_{4}OH\right]}$
$6+\log\frac{\left[1\right]}{\left[0.1\right]}$
$=6+\log 10$
$=6+1=7$