Answer: 5.0 x 10-12 M
Explanation:
It is well known that; pH + pOH = 14.
pOH = - log [ OH-]
= - log [ 2.0 x 10 ∧-3]
= 3 - log 2
= 3 - 0.301 = 2.7 approximately.
recall that, pH + pOH = 14, therefore; pH = 14 - 2.7 = 11.3
pH = - log [ H3O+]
11.3 = - log [H3O+], take the antilog of 11.3, gives us;
[H3O+] = antilog of - 11.3, which gives 5.0 x 10-12 M
