Solution to PS 1 #4

a) Since HCl is a strong acid, 10^-5 N HCl yields 10^-5 M H⁺. So the pH= -log (10^-5) = 5

b) Since HCl is a strong acid, 3 x 10^-6 N HCl yields 3 x 10^-6M H⁺. So the pH= -log (3 x 10^-6) = 5.5

c) Watch out! Most of the H⁺ in this case comes from the H₂O. In this case the [H⁺]=1.01 x 10^-7 M. So the pH= -log (1.01 x 10^-7) = 7.0

d) H₂SO₄ is a strong acid that dissociates giving 2 H⁺ for each H₂SO₄ molecule. So 7 mM H₂SO₄ gives a [H⁺] = 14 mM= 1.4 x 10^-2 M. So the pH= -log(1.4 x 10^-2) = 1.9

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