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

#[OH^-]# ion concentration .

1 Answer
Apr 23, 2018

#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")#