Did the test solution react with the supernatant from the test tube that had the largest amount of precipitate? what can you infer about the molar ratio of this reaction?

Answer: -

The test solution reacted with the supernatant from the test tube. In trial number 3 there was the largest amount of precipitate.

An amount of 0.019 g of precipitate was found. In trial 3, 3 mL CuSO₄ and 3 mL Na₂S was taken. Thus they were at a 1: 1 ratio.

From the fact that the most amount of precipitate was formed when the two reactants were at 1:1 ratio implies that at that ratio, all of the reactants reacted.

Thus the mole ratio of the reaction is 1 : 1.