A 1.00 l buffer solution is 0.250 m in hf and 0.250 m in naf. Calculate the ph of the solution after the addition of 100.0 ml of 1.00 m hcl. The ka for hf is 3.5 * 10-4.

Question

Chemistry

Hugo Burns

9 June, 02:32

A 1.00 l buffer solution is 0.250 m in hf and 0.250 m in naf. Calculate the ph of the solution after the addition of 100.0 ml of 1.00 m hcl. The ka for hf is 3.5 * 10-4.

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Answers (1)

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Leilani Roach · Answer 1

pH = 3.09

Explanation:

Solve this problem using the Henderson-Hasselbach formula after calculating the changes in the buffer following the addition of HCl. The addition of the acid consumes the conjugate base in a one to one reaction. The moles present are calculated by multiplying the molarity by the volume in liters.

R: HF ⇆ H⁺ + F⁻

I: 0.250 mol 0.250 mol

C: + 0.100 mol - 0.100 mol

E: 0.350 mol 0.150 mol

pH = pKa + log ((F⁻) / (HF))

pH = - log (3.5 x 10 ⁻⁴) + log (0.15 / 0.35)

pH = 3.46 + (-0.37) = 3.09

Note: Here we do not need to calculate the change in concentrations since the volume appears in the ratio and cancel themselves.