Answer to Question #316118 in Chemistry for Lucas

Question

Calculate the hydroxide ion concentration at 25 in a solution whose pH is 5.78. (kW=1*10_14moldm at25)

Answer 1

Solution:

hydroxide ion = [OH^−]

pH = −log[H₃O⁺]

Therefore,

[H₃O⁺] = 10^−pH = 10^−5.78 = 1.66×10^−6

[H₃O⁺] = 1.66×10^−6 M

K_w = [H₃O⁺] × [OH^−]

Therefore,

[OH^−] = K_w / [H₃O⁺] = (1.0×10^−14) / (1.66×10^−6) = 6.02×10^−9

[OH^−] = 6.02×10^−9 M

Answer: The hydroxide ion (OH^−) concentration is 6.02×10^−9 M