# A solution is formed by mixing 30 mL of 0.1 M H_3PO_4 , 60 mL of 0.15 M Na_3PO_4 and 20 mL of...

## Question:

A solution is formed by mixing 30 mL of 0.1 M {eq}H_3PO_4 {/eq}, 60 mL of 0.15 M {eq}Na_3PO_4 {/eq} and 20 mL of 0.1 M HCl. What is the pH of the resulting solution?

Phosphoric acid:

{eq}K1= 7.11 \times 10^{-3} \\ K2= 6.34 \times 10^{-8} \\ K3= 4.2 \times 10^{-13} {/eq}

## pH and Hydronium Ion Concentration

The pH is the measure of a solution's acidity or basicity, which has values ranging from 1 to 14. A pH value of 1 indicates a strongly acidic solution, 14 indicates a strongly basic solution, and 7 indicates a neutral solution. The pH is also the measure of the hydronium ion concentration present in the solution. It is given as the negative base 10 logarithms of the molar concentration of hydrogen ions as indicated by the formula below:

{eq}pH=-log_{10}[H^+] {/eq}

The simplest way of measuring the pH value of a solution is through litmus paper. A red litmus paper stays red if the solution is acidic, or turns blue if the solution is basic. Another way of measuring the pH is through a pH meter.