2. A student mixed the following reactants, using the general procedure for the experiment: 10.0 mL of 0.10 M KI, 10.0 mL of 0.0010 M Na2S2O3, 20.0 mL of 0.040 M KBrO3, and 10.0 mL of 0.10 M HCl. It took about 75 seconds for the mixture to turn blue. Calculate the concentrations of each reactant in the mixture after all solutions are mixed.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%