Q&A for How to Do Stoichiometry

Chloric acid's molar mass is 84.5 g/mol, so 17.5 grams is (17.5 g)/(84.5 g/mol) = 0.207 mol. The reaction is Ca + 2HClO3 --> H2 + Ca(ClO3)2 This shows that for every 2 moles of chloric acid, 1 mol of hydrogen forms. Thus, 0.207 moles chloric acid leads to 0.207/2 = 0.1036 moles hydrogen. The molar mass of hydrogen gas is 2.02 g/mol, so 0.1036 mol hydrogen is (0.1036 mol)*(2.02 g/mol) = 0.2088 grams hydrogen.

MgCl2 + 2HF --> MgF2 + 2HCl. 6.75 mol MgCl2 x (2 mol HCl/1 mol MgCl2) = 13.5 mol HCl.

Molar mass/L is 1 mole. The volume occupied by 1 mole of a substance at a given T and P is molar volume. Therefore, molar mass(M) divided by density will give you the molar volume of a liquid.

To determine a limiting reagent, follow all of the steps until you get to the ratio section. First, find the ratios of the reactants, then use the moles of each reactant and cross multiply to find how much of each reactant is required. The one that is less is the limiting reagent.