Answer to Question #167782 in Chemistry for Mace Delos Santos

Question

What is the [H₃O^-] and [OH^-] ion concentration respectively in a solution that contains 0.155 M HNO₃?

Answer 1

Solution:

HNO₃ + H₂O → H₃O⁺ + NO₃^-

After complete dissociation: C_M(HNO₃) = [H₃O⁺] = [NO₃^-]

So concentration of [H₃O⁺] = 0.155 M

[H₃O⁺] = 0.155 M

For any aqueous solution at 25^∘C:

K_w = [H₃O⁺] × [OH^-] = 1×10^-14

Hence,

[OH^-] = K_w / [H₃O⁺]

[OH^-] = (1×10^-14) / (0.155) = 6.45×10^-14

[OH^-] = 6.45×10^-14 M

Answer: [H₃O⁺] = 0.155 M; [OH^-] = 6.45×10^-14 M.