Hydrated cobalt(II) chloride crystals are pink in colour. On heating, they lose water and produce blue anhydrous cobalt(II) chloride. $\text{hydrated cobalt(II) chloride} \rightleftharpoons \text{anhydrous cobalt(II) chloride} + \text{water}$. A few drops of vinegar were put onto anhydrous cobalt(II) chloride. The colour then changed from blue to pink. What does this colour change indicate about vinegar?
- AIt contains an acid.
- BIt contains water.
- CIt is an alkali.
- DIt is anhydrous.