Four different aqueous solutions, W, X, Y, and Z, each with a concentration of 0.10 mol dm-3, are tested at 298 K. Their pH\text{pH}pH is measured, and their reaction with a few drops of acidified potassium manganate(VII) solution, KMnO4(aq)\text{KMnO}_4\text{(aq)}KMnO4(aq), is observed.
| Solution | pH\text{pH}pH | Observation with acidified KMnO4(aq)\text{KMnO}_4\text{(aq)}KMnO4(aq) |
|---|---|---|
| W | 1.0 | Purple solution remains purple |
| X | 2.4 | Purple solution decolourises |
| Y | 2.9 | Purple solution remains purple |
| Z | 7.0 | Purple solution remains purple |
Which solution is a weak acid that also acts as a reducing agent?
Solution W
Solution X
Solution Y
Solution Z