Question

Determine the pH of each of the following solutions.

a.

8.09×10⁻² M HClO4

Express your answer to three decimal places.

b.

a solution that is 4.4×10⁻² M in HClO4 and 5.2×10⁻² M in HCl

Express your answer to two decimal places.

c.

a solution that is 1.04% HCl by mass (Assume a density of 1.01 g/mL for the solution.)

Express your answer to three decimal places.

Thank you!!

Answer 1

a)

HClO₄ is a strong acid, hence

[H+] = 8.09 x 10^-2 M

pH = -log[H+] = -log[8.09 x 10^-2] = 1.09

Answer: pH = 1.09

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b)

HClO₄ & HCl both are strong acids, so [H+] are additive

[H+] = 4.4 × 10⁻² M + 5.2 × 10⁻² M = 9.6 x 10^-2 M

pH = -log[H+] = -log[9.6 x 10^-2] = 1.02

Answer: pH = 1.02

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c)

1 liter = 1010 g

HCl = 1.04 %

(1.04/100) x 1010 = 10.504 g HCl

moles HCl = 10.504 g / 36.4609 g/mol = 0.28808943279 mol

[H+] = 0.28808943279 M

pH = -log[H+] = -log[0.28808943279] = 0.540

Answer: pH = 0.540 -----------------------> use exact this number including zero to fulfill 3 sf

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