The ph of an aqueous solution is 4.32. what is the [oh–]?

2.10 x 10^-10 M. Ans

pH + pOH = 14
Where, pOH is the power of hydroxide ion concentration and pH is the power of concetration of the H+ ion.
Now, pOH = 14 - 4.32
= 9.68
Now, the concentration of [H+] is 10-7 M, then pH is 7 and for [OH-] = 10-7 M, the pOH is also 7.

Now, pOH = -log[OH-]
[OH-] = 10^- pOH
= 10^-9.68
= 2.10 x 10^-10 M