Question

What happens to the pH of a solution when the solution is diluted 2 times?

Answer 1

In most cases dilution of a solution will decrease the concentration of hydroxide or hydronium ions in solution.

Hence, if the solution is acidic for instance with `"pH" = 2`,

`[H_3O^+] = 10^-2 M`

The solution is diluted to two liters from one liter,

`10^-2M * 1/(2L) = 5*10^-3M`
`therefore "pH" approx 2.30`

Moreover, the solution is diluted to three liters from two liters,

`5*10^-3M * 1/(3L) approx 1.7*10^-3M`
`therefore "pH" approx 2.78`

From the preceding quantitative analysis, we can say the acidity of the solution decreases, and the `"pH"` will increase. Likewise, we may conclude that a basic solution becomes less basic upon dilution.