Question

A solution of an acid has $ [{{H}^{+}}]=2\times {{10}^{-5}}. $ Find out the concentration of $ O{{H}^{-}} $ ions.

• A. $ 5\times {{10}^{-10}}N $
• B. $ 4\times {{10}^{-10}}N $
• C. $ 2\times {{10}^{-5}}N $
• D. $ 9\times {{10}^{-4}}N $

Answer 1

Answer: (A)

$ [{{H}^{+}}]\,[O{{H}^{-}}]={{K}_{w}} $ $ 2\times {{10}^{-5}}\times [O{{H}^{-}}]=1\times {{10}^{-14}} $ $ [O{{H}^{-}}]=\frac{1\times {{10}^{-14}}}{2\times {{10}^{-5}}} $ $ =0.5\times {{10}^{-9}} $ $ =5\times {{10}^{-10}} $