Answer to Question #43443 in Physical Chemistry for ashley

Question

If a solution is 0.001 M in NaOH, what is the pH?

a) 3

b) 4

c) 7

d) 11

Answer 1

NaOH completely dissociates in water solution:
NaOH --> Na⁺ + OH^-
Therefore, the concentration of OH- ions is equal to the concentration of the solution:
c(OH^-) = c(NaOH) = 0.001
According to water self-ionization equation,
K_w = c(H⁺)c(OH^-) = 10^-14
Hence,
c(H⁺) = K_w/c(OH^-) = 10^-14/10^-3 = 10^-11
pH = - lg c(H⁺) = 11
So, the correct option is (d): 11