Question

Find the pH of each mixture of acids.

Part A

7.0×10⁻² M in HNO3 and 0.165 M in HC7H5O2

Part B

1.5×10⁻² M in HBr and 2.0×10⁻² M in HClO4

Part C

9.5×10⁻² M in HF and 0.230 M in HC6H5O

Part D

0.110 M in formic acid and 4.5×10⁻² M in hypochlorous acid

Answer 1

Part A

[H+] in HNO3 = 7.0 x 10^-2 M

[H+] in HC7H5O2 = sqrt (Ka x C)

                             = sqrt (6.3 x 10^-5 x 0.165)

                             = 3.224 x 10^-3 M

[H+] = 0.07 + 0.003224 = 0.073 M

pH = -log (0.073)

pH = 1.14

Part B

[H+] = 0.015 + 0.020 = 0.035 M

pH = -log (0.035)

pH = 1.46

Part C

9.5×10⁻² M in HF and 0.230 M in HC6H5O

[H+] = sqrt (6.3 x 10^-4 x 0.095 + 1.3 x 10^-10 x 0.230)

        = 2.15 x 10^-3 M

pH = -log (2.15 x 10^-3)

pH = 2.67

Part D

0.110 M in formic acid and 4.5×10⁻² M in hypochlorous acid

[H+] = 4.45 x 10^-3 M

pH = 2.35