Question

If 40.00 mL of a 0.05 M solution of an unknown monobasic acid is titrated with a 0.10 M solution of NaOH, q(Ka(HA)=6.28×10⁻⁵)

a. Calculate the pH of a 0.05 M solution of an unknown monobasic acid.

Answer 1

To calculate the pH of a 0.05 M solution of an unknown monobasic acid, we use the equation Ka = [H₃O⁺] [A-] / [HA] and rearrange it to solve for [H₃O⁺]. Plugging in the values, we find a concentration of 6.28×10⁻⁵ M. Using the formula pH = -log[H₃O⁺], we calculate a pH of 4.2045.

Step-by-step explanation:

In order to calculate the pH of a 0.05 M solution of the unknown monobasic acid, we need to calculate the concentration of H3O+ ions. Since the acid is monobasic, it will only produce one H3O+ ion for every molecule of acid that dissociates.

Using the equation Ka = [H₃O⁺] [A-] / [HA], we can rearrange it to solve for [H₃O⁺].

Let's plug in the values:

Ka = 6.28×10⁻⁵

[HA] = 0.05 M

[A-] = 0.05 M (since the concentration of the conjugate base will be equal to the concentration of the acid)

Now we can solve for [H₃O⁺]:

6.28×10⁻⁵ = [H₃O⁺] (0.05) / 0.05

[H₃O⁺] = 6.28×10⁻⁵ M

Finally, we can calculate the pH using the equation pH = -log[H₃O⁺]:

pH = -log(6.28×10⁻⁵) = 4.2045