Chapter 15

Q. 15.5

The concentration of H_{3}O^{+} ions in a sample of lemon juice is 2.5\times 10^{-3}  M. Calculate the concentration of OH^{-} ions, and classify the solution as acidic, neutral, or basic.


When [H_{3}O^{+}] is known, the OH^{-} concentration can be found from the expression [OH^{-}] = K_{w}/[H_{3}O^{+}].

Known Unknown
K_{w}=1.0\times 10^{-14} [OH^{-}]
[H_{3}O^{+}]=2.5\times 10^{-3}  M


Verified Solution

[OH^{-}]=\frac{K_{w}}{[H_{3}O^{+}]}=\frac{1.0\times10^{-14}}{2.5\times10^{-3}}=4.0\times10^{-12}  M

Because  [H_{3}O^{+}]>[OH^{-}], the solution is acidic.