Question

For each strong acid solutions, determine [H3O+],[OH−], and pH. (So, there should be three answers for each question).

1. 0.22 M HCl

2. 1.8×10⁻² M HNO3

3. a solution that is 6.1×10⁻² M in HBr and 1.9×10⁻² M in HNO3

4. a solution that is 0.755% HNO3 by mass (Assume a density of 1.01 g/mL for the solution.)

Answer 1

1) As HCl is a strong acid - there are , [H₃O⁺] = 0.22 M, [OH^-] = Kw/ [H₃O⁺] = (1.0*10^-14/0.22) = 4.54e-14 M,

pH = -log  [H₃O⁺] = - log(0.22) = 0.65

2)

As HNO is a strong acid - there are , [H₃O⁺] = 1.8*10^-2 M, [OH^-] = Kw/ [H₃O⁺] = (1.0*10^-14/1.8*10^-22 M) = 5.55e-13 M,

pH = -log  [H₃O⁺] = - log(1.8*10^-2 M) = 1.77

3) Total [H₃O⁺] = 6.1*10^-2 + 1.9*10^-2 = 8*10^-2 M, [OH^-] = 1.25*10^-13 M. pH = - log [H₃O⁺] = -log (8*10^-2 )

   = 1.09

4) Number of mols of HNO₃ = 0.755 g / 63 g/mol = 0.0119 mol

Thus - Molarity = 0.0119 mol / 0.1 L = 0.119 M