Question

Why would solution IV be considered the most concentrated base out of the four substances?

Answer 1

You determine which solution is the most concentrated base by comparing their hydroxide ion concentrations, [OH−]. The solution with the largest [OH−] is the most concentrated base.

Quick ways to get [OH−]:

- If you know pH: pOH = 14.00 − pH (at 25 °C), then [OH−] = 10^(−pOH).
- If you know pOH directly: [OH−] = 10^(−pOH).
- If you know [H+]: use Kw = [H+][OH−] = 1.0×10^(−14) (at 25 °C) so [OH−] = Kw / [H+].

So solution IV is considered the most concentrated base because it has the highest pH (or lowest pOH) of the four, which corresponds to the largest [OH−].

Note: “most concentrated base” means largest hydroxide concentration, not necessarily the strongest base (Kb); a concentrated weak base can give more [OH−] than a very dilute strong base. If you give the pH or other data for the four solutions I–IV I can compute the [OH−] values and show the comparison.