Question

Solution I has $pH=2.4$, Solution II has $pH=3.6$, Solution III has $pH=4.6$ Then $pH$ of resulting solution is:

• A. 5.5
• B. 1.54
• C. 3.02
• D. 2.84

Answer 1

The correct option is D 2.84

Solution 1: $pH=2.4\Rightarrow \left[H^{+}\right]={10}^{-2.4}=3.98\times {10}^{-3}M$

Solution 2: $pH=3.6\Rightarrow \left[H^{+}\right]={10}^{-3.6}=0.251\times {10}^{-3}M$

Solution 3: $pH=4.6\Rightarrow \left[H^{+}\right]={10}^{-4.6}=0.025\times {10}^{-3}M$

Total $\left[H^{+}\right]=\frac{(3.98+0.251+0.025)}{3}\times {10}^{-3}$

$=4.256\times {10}^{-3}M$

$\therefore pH=-\log \left[H^{+}\right]=-\log \left[\right(4.256\times {10}^{-3}\left)/3\right]$

$=-\log (1.42\times {10}^{-3})$

$pH$ of resulting solution= $2.84$ .