Question

Equal volumes of three acid solutions of pH 3, 4 and 5 are mixed in a vessel. What will be the $H^{+}$ ion concentration in the mixture?

• A. $1.11\times {10}^{-4}M$
• B. $3.7\times {10}^{-4}M$
• C. $3.7\times {10}^{-3}M$
• D. $1.11\times {10}^{-3}M$

Answer 1

The correct option is B $3.7\times {10}^{-4}M$

Molarity of the mixture:

$M=\frac{M_1{V}_1+M_2{V}_2+M_2{V}_3}{V}$

For I st solution $(pH=3)\left[H_3{O}^{+}\right]={10}^{-3}M$

For II nd solution $(pH=4)\left[H_3{O}^{+}\right]={10}^{-4}M$

For III rd solution $(pH=5)\left[H_3{O}^{+}\right]={10}^{-5}M$

Total $\left[H_3{O}^{+}\right]=\frac{{10}^{-3}+{10}^{-4}+{10}^{-5}}{3}$

$\left[H_3{O}^{+}\right]=0.00037$

$\left[H_3{O}^{+}\right]=3.7\times {10}^{-4}M$