What are the (a) H+ ion concentration, (b) pH, (c) OH- ion concentration, and (d) pOH of a 0.001 M solution of HCl?
To find the H+ ion concentration, we can use the equation that HCl completely ionizes in water to produce H+ ions. Since the concentration of HCl is 0.001 M, the concentration of H+ ions will also be 0.001 M.
(a) H+ ion concentration = 0.001 M
The pH is a measure of the acidity or alkalinity of a solution and is defined as the negative logarithm (base 10) of the H+ ion concentration. Therefore, we can use the formula:
pH = -log[H+]
(b) pH = -log(0.001) ≈ 3
The OH- ion concentration can be calculated using the fact that water molecules (H2O) will undergo autoionization, where a small fraction will dissociate into H+ and OH- ions. However, in the presence of strong acids like HCl, the concentration of H+ ions will be much greater compared to the autoionization of water, and we can approximate the OH- ion concentration to be zero.
(c) OH- ion concentration ≈ 0
The pOH is another measure of the acidity or alkalinity of a solution and is defined as the negative logarithm (base 10) of the OH- ion concentration. Since the OH- ion concentration is approximately zero, the pOH will be infinite.
(d) pOH ≈ ∞
To summarize:
(a) H+ ion concentration = 0.001 M
(b) pH ≈ 3
(c) OH- ion concentration ≈ 0
(d) pOH ≈ ∞