Question

A 50.0 mL sample of 0.040 M HCl is titrated with 0.040 M NaOH. What is the pH of the solution after 30.0 mL of NaOH have been added to the acid?

a. 3.85
b. 2.96
c. 2.00
d. 2.49

Answer 1

To calculate the pH of the solution after adding NaOH to HCl, we need to calculate the moles of HCl and NaOH and then convert the concentration into pH using the formula pH = -log[H+]. In this case, the pH is approximately 2.96.

Step-by-step explanation:

In this question, we are given a 50.0 mL sample of 0.040 M HCl and we are titrating it with 0.040 M NaOH. We need to determine the pH of the solution after 30.0 mL of NaOH have been added to the acid.

We can use the formula pH = -log[H+], where [H+] is the concentration of H+ ions in the solution. In this titration, NaOH reacts with HCl in a 1:1 ratio to form water (H2O) and NaCl.

First, we need to calculate the moles of HCl in the 50.0 mL sample using the formula moles = concentration × volume. Then, we can calculate the moles of NaOH in the 30.0 mL solution. Since NaOH and HCl react in a 1:1 ratio, the moles of HCl consumed will be equal to the moles of NaOH added. Finally, we can calculate the concentration of H+ ions in the solution using the formula concentration = moles/volume and then convert it to pH using the formula pH = -log[H+].

Using these calculations, we find that the pH of the solution after adding 30.0 mL of NaOH is approximately 2.96.