Question

In the following solutions,the concentration of different acids are given,which mixture of the acid has highest pH:

• A. $\frac{M}{10}{H}_{2}S{O}_4,\frac{M}{20}HN{O}_3,\frac{M}{10}HCl{O}_4$
• B. $\frac{M}{20}{H}_{2}S{O}_4,\frac{M}{10}HN{O}_3,\frac{M}{20}HCl{O}_4$
• C. $\frac{M}{20}{H}_{2}S{O}_4,\frac{M}{10}HN{O}_3,\frac{M}{40}HCl{O}_4$
• D. $\frac{M}{20}{H}_{2}S{O}_4,\frac{M}{5}HN{O}_3,\frac{M}{5}HCl{O}_4$

Answer 1

The correct option is C $\frac{M}{20}{H}_{2}S{O}_4,\frac{M}{10}HN{O}_3,\frac{M}{40}HCl{O}_4$

As we know, $pH=-log\left[H^{+}\right]$

So higher the conc. of hydrogen ion, lower will be the pH.

Here, $\frac{M}{20}{H}_{2}S{O}_4,\frac{M}{10}HN{O}_3,\frac{M}{40}HCl{O}_4$

$\left[H^{+}\right]=2\times \frac{1}{20}+\frac{1}{10}+\frac{1}{40}$

has the lowest conc. of hydrogen ions so it will have highest pH.