Question

What is the pH of a solution made by dissolving 0.1 moles of NaOH and 0.2 moles of HCl in 2 L of water?

Answer 1

pH = 1.30

Step-by-step explanation:

The reaction that would take place between HCl and NaOH is:

• HCl + NaOH → NaCl + H₂O

In this problem, the 0.1 moles of NaOH would react with 0.1 moles of HCl, leaving 0.1 moles of HCl unreacted.

These 0.1 HCl moles are dissolved in 2 liters, thus the concentration of H⁺ species is:

• [H⁺] = moles / volume

• [H⁺] = 0.1 mol / 2 L =0.05 M

Finally we calculate the pH:

• pH = -log[H⁺]

• pH = -log[0.05]

• pH = 1.30