Universal indicator is made up of several dyes. The reversible reaction for one dye, $\text{IndOH}$, is shown. $\text{IndOH}(aq) + \text{H}^+(aq) \rightleftharpoons \text{Ind}^+(aq) + \text{H}_2\text{O}(l)$ A few drops of universal indicator solution are placed into $50\,\text{cm}^3$ of water. Then a few drops of dilute hydrochloric acid are added to this mixture. Which row shows what occurs when the acid is added?
- ApH decreases | colour shifts towards colour X
- BpH decreases | colour shifts towards colour Y
- CpH increases | colour shifts towards colour X
- DpH increases | colour shifts towards colour Y