Question

Calculate the pH that results when the following solutions are mixed

1. 35 mL of 0.20 M formic acid 𝐻𝐶𝑂𝑂𝐻, 𝐾𝑎 = 1.77 × 10−4
2. 55 mL of 0.10 M sodium formate 𝐻𝐶𝑂𝑂𝑁𝑎
3. 110 mL of water

Answer 1

Use the HH equation.
1. 35 mL of 0.20 M formic acid 𝐻𝐶𝑂𝑂𝐻, 𝐾𝑎 = 1.77 × 10−4
2. 55 mL of 0.10 M sodium formate 𝐻𝐶𝑂𝑂𝑁𝑎
3. 110 mL of water
Total volume is 200 mL.
(HCOOH) = 0.20 M x (35/200) = ?
(HCOONa) = 0.10 M x (55/200).
Convert Ka to pKa.Substitute into the HH equation. Solve for pH.
Note that HCOOH is the acid and HCOONa is the base.
Post your work if you get stuck.

Answer 2

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Answer 3

Calculate the pH that results when the following solutions are mixed
1. 35 mL of 0.20 M formic acid 𝐻𝐶𝑂𝑂𝐻, 𝐾𝑎 = 1.77 × 10−4
2. 55 mL of 0.10 M sodium formate 𝐻𝐶𝑂𝑂𝑁𝑎
3. 110 mL of water