Stoichiometry Exercise

Is a branch of chemistry that deals with the quantitative relationships that exist between the reactants and products in chemical reactions. In a balanced chemical reaction, the relations among quantities of reactants and products typically form a ratio of whole numbers. For example, in a reaction that forms ammonia (NH₃), exactly one molecule of nitrogen (N₂) reacts withc)  three molecules of hydrogen (H₂) to produce two molecules of NH₃:

N₂ + 3H₂ → 2NH₃

Example 1 : Ca(s) + 2HCl(aq) ----> CaCl2(aq) + H2(g)

a) How many atoms of Ca are needed to produce 1 molecule og Hydrogen?
Ans : Base on the equation : 1 mole of Ca/1 mole of Hydrogen = 1

b) How many moles of HCl are needed to produce 0.452 moles of CaCl2?

Ans : 0.452Ca x 2 moles of HCl/1 mole of Ca = 0.904mol

c) How many grams of Ca will react with 1.05moles of HCl?

Ans : 1.05moles of HCl x 1mole of Ca/2Hcl = 0.525moles of Ca

d) How many grams of CaCl2 will be formed when 2.00g of hydrogen is formed?

Ans : 2.00g/2 moles of H2 x 1 mole of CaCl2/1 mole of H x (40.1 + 35.5 x 2)g = 111.1gCaCl2

e) How many moles of of HCl are needed to form 6.12grams of CaCl2?

Ans : 6.12g of CaCl2/(40.1 + 35.5 x 2)mol of CaCl2 x 2 moles of HCl/1 mole of CaCl2 = 0.11 mol of HCl