Final answer:
Very little benzoic acid will dissolve in cold water during the procedure, and this can potentially be detected with litmus paper if the solution becomes slightly acidic, indicated by a color change from blue to red.
Step-by-step explanation:
In step 1 of the procedure, where 10 mL of cold water (20 °C) is used to dissolve the salt, it's important to understand the solubility of benzoic acid in water. At 25°C, a saturated solution of benzoic acid has about 5% of the acid dissociated into benzoate anions and hydrated protons, with the remaining 95% as hydrated neutral molecules. Since the solubility of benzoic acid in cold water (20 °C) will be even lower than at 25 °C, very little, if any, benzoic acid will dissolve in the water used in the procedure.
To detect if benzoic acid has dissolved in water, litmus paper can be used. Benzoic acid is a weak acid and if it dissolves, the solution will become slightly acidic. The litmus paper will show this by turning from blue to red, as blue litmus paper is used to detect acidity. However, due to the low solubility of benzoic acid in cold water, there might not be a significant enough change in pH value to be detected by litmus paper.