19.4 mL of 0.75M hydrochloric acid is used to titrate 24.3mL of sodium hydroxide. Write the balanced equation. What is the molarity of sodium hydroxide? Find the pH of sodium hydroxide.

Question

1. Identify the acid and the base in the reaction

Answer 1

The balanced equation is as follows:

HCl(aq) + NaOH(aq) -> HOH(aq) + NaCl(aq)

First we have to find the moles of NaOH using HCl:

19.4 mL = 0.0194 L * (0.75 mol/L) * (1 mol NaOH/ 1 mol HCL) = 0.01455 mol NaOH.

To find the molarity of NaOH, we will divide the mol of NaOH by the volume of NaOH:

0.01455 mol NaOH/0.0243 L = 0.60 M

As you may know, pH is simply the concentration of Hydrogen ions in a solution and is give by the formula , pH = - log([H^+]). We can use a similar equation to find the concentration of Hydroxide ions in a solution which is given by the formula, pOH = -log([OH^-]).

The ion product constant for water, which is Kw = 1.0 x 10^-14 = [H⁺][OH^-].

By taking the negative logarithm of all concentrations and substituting in the definitions of pH and pOH, we have Kw = pH + pOH = 14. We will use this equation to solve for pH

pOH = -log([OH]) = - log(0.60) = 0.22

pH = 14 - pOH = 14 - 0.22 = 13.78

The pH of NaOH is 13.78.