Question

If equal volumes of $0.1 \,M \,HBr$ and $0.1\, M\, KOH$ are mixed, then which of the following is/are correct about the resulting solution ?
(1) $\left[ H _{3} O ^{+}\right]=1.0 \times 10^{-7}\, mol\, L ^{-1}$
(2) $\left[ OH ^{-}\right]=1.0 \times 10^{-7} \,mol\, L ^{-1}$
(3) $\left[ K ^{+}\right]=0.05\, mol\, L ^{-1}$
(4) $\left[ Br ^{-}\right]=0.10\, mol\, L ^{-1}$

• A. 1, 2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (A)

$HBr + KOH \rightarrow KBr + H _{2} O$
Volume of resulting solution will be doubled and the solution will be neutral.
Hence, $\left[K^{+}\right]=\left[B r^{-}\right]=\frac{0.1}{2}=0.05\, mol\, L^{-1}$
$\left[ H _{3} O ^{+}\right]=\left[ OH ^{-}\right]=10^{-7} \,mol\, L^{-1}$