Question

80.0 mL of 0.30 M NaOH and 80.0 mL of 0.30 M HCl are mixed together. What is the approximate pH

Answer 1

Answer:

• Neutral

Explanation:

The number of moles of solute is equal to product of the molar concentration (molarity) and the volume (in liters) of solution.

Since the volumes and the molar concentrations of the NaOH and HCl solutions mixed are equal, each one of them contributes the same number of moles of solute.

Since every mol of NaOH produces one mol of OH⁻ ions and every mol of HCl produces one mol of H⁺ ion, the number of moles of OH ⁻ and H⁺ in solution are equal.

Thus, OH⁻ and H⁺ ions will be neutralized by the reaction:

• OH⁻ (aq) + H⁺ (aq) ⇄ H₂O (l)

Which is strongly shifted to the right and has neutral pH.

Hence, you conclude that the approximate pH of the solution is neutral.