Calculate the pH of a solution formed by mixing 150.0 mL of 0.10 M HC₇H₅O₂ with 100.0 mL of 0.30 M NaC₇H₅O₂.The K_a for HC₇H₅O₂ is 6.5 × 10^-5. A) 4.19 B) 9.69 C) 4.49 D) 4.31 E) 10.51

Question

Quizplus · Accepted Answer

First, we need to calculate the moles of each species present in the solution.

Moles of HCS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0:

0.10 mol/L * 0.150 L = 0.015 mol

Moles of NaCS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0:

0.30 mol/L * 0.100 L = 0.030 mol

Now, we need to determine which species will act as the acid and which as the base in this solution. Since HCS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0 is a weak acid, it will donate a proton to water and act as the acid. NaCS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0 will accept the proton and act as the base.

HCS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0 + H2O --> H3O+ + CS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0

Using the Ka expression for HCS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0, we can solve for the concentration of H3O+ and thus the pH:

Ka = [H3O+][CS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0] / [HCS1U1B17S1U1B0HS1U1B15S1U1B0OS1U1B12S1U1B0]

6.5 × 10S1U1P1-5 = x^2 / (0.015 - x)

Assuming x << 0.015, we can simplify this to:

6.5 × 10S1U1P1-5 = x^2 / 0.015

x = 2.02 × 10S1U1P1-4

pH = -log[H3O+] = -log(2.02 × 10S1U1P1-4) = 4.49

Therefore, the answer is (C).

Calculate the PH of a Solution Formed by Mixing 150