How to Calculate pH of a Solution

What is the pH of a solution?

A student combines 0.20 mole of NaOH and 0.25 mole of HCl in water to make 2.0 liters of solution. The pH of this solution is 0.60. How can we calculate the pH of the solution?

Calculating pH of the Solution

The pH of a solution indicates its acidic or basic nature. In this case, the student has created a solution by mixing NaOH and HCl. The reaction between NaOH and HCl results in the formation of salt (NaCl) and water (H2O).

When NaOH and HCl react, they do so in a 1:1 ratio, which means all the HCl is neutralized by NaOH, leaving only NaCl and H2O in the solution. To find the pH of the solution, we need to calculate the concentration of H+ ions present.

The amount of H+ ions from HCl can be calculated by multiplying the molarity of HCl (0.25 mol/L) by the volume of the solution (2.0 L). This calculation gives us 0.50 moles of H+. Since this amount of H+ ions is in 2.0 liters of solution, the concentration of H+ ions is 0.25 M.

To determine the pH of the solution, we can use the formula pH = -log[H+]. By plugging in the calculated concentration of H+ ions (0.25 M), we get:

pH = -log(0.25) = 0.60

Therefore, the pH of the solution created by combining 0.20 mole of NaOH and 0.25 mole of HCl in 2.0 liters of water is 0.60.