A 2.98-g sample of NaOH(s) is added to enough water to make 300.0 mL of solution at 25°C. What is the pH of this solution?

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Quizplus · Accepted Answer

The molar mass of NaOH is approximately 40 g/mol, so 2.98 g of NaOH is 2.98 g / 40 g/mol = 0.0745 mol. When dissolved in 300 mL (or 0.3 L) of water, the concentration of NaOH is 0.0745 mol / 0.3 L = 0.2483 M. NaOH is a strong base that completely dissociates in water, so the concentration of OH- ions is also 0.2483 M. The pOH of the solution can be calculated using the formula pOH = -log[OH-], which gives pOH = -log(0.2483) ≈ 0.605. Since pH + pOH = 14 for aqueous solutions at 25°C, the pH of the solution is 14 - 0.605 = 13.395, which rounds to 13.40.

A 298-G Sample of NaOH(s) Is Added to Enough Water to to Make