Question

If 10.0 g of NaF and 15.0 g of HF are dissolved in water to make 2.0 L of solution, what is the pH of the resulting solution?

Answer 1

Answer:

2.68

Explanation:

Step 1: Calculate the molar concentrations of the solutes

We will use the following expression.

M = mass of solute / molar mass of solute × liters of solution

[HF] = 15.0 g / 20.01 g/mol × 2.0 L = 0.37 M

[NaF] = 10.0 g / 41.99 g/mol × 2.0 L = 0.12 M

Step 2: Calculate the pH of the solution

We have a buffer system formed by a weak acid (HF) and its conjugate base (F⁻ coming from NaF). We can calculate the pH of the solution using Henderson-Hasselbach equation.

pH = pKa + log [F⁻]/[HF]

pH = 3.17 + log (0.12 M/0.37 M)

pH = 2.68

Answer 2

The pH of the resulting solution is 2.68.

What is pH?

pH is potential hydrogen. It is the measurement of the acidity and basicity of any solution.

Step 1: Calculate the molar concentrations of the solutes

M = mass of solute / molar mass of solute × liters of solution

$\rm [HF] = \dfrac{15.0 g}{20.01 g/mol } \times 2.0 L = 0.37 M[NaF] = \dfrac{10.0 g}{ 41.99 g/mol} \times 2.0 L = 0.12 M$

Step 2: Calculate the pH of the solution

pH = pKa + log [F⁻]/[HF]

pH = 3.17 + log (0.12 M/0.37 M)

Thus, the pH of the resulting solution is 2.68

Learn more about pH

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