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)

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