Question

What is the concentration of `OH^-` ions in pure water at 20 degrees Celsius?

`[OH^-]` ion concentration .

Answer 1

`sf(8.25xx10^(-8)color(white)(x)"mol/l")`

Explanation:

Pure water dissociates:

`sf(H_2OrightleftharpoonsH^(+)+OH^(-))`

`sf(K_w=[H^(+)][OH^(-)]=0.681xx10^(-14))` at `sf(20^@C)`

Since `sf([H^+]=[OH^(-)])` we can say:

`sf([OH^(-)]=sqrt(0.681xx10^(-14))=8.25xx10^(-8)color(white)(x)"mol/l")`