Answers:
Mole
1. How many moles of PbSO4 are in 108.1 g of the compound?
.3564 mol PbSO4
%comp
2. A sample of iron oxide has a mass of 1.596 g. On analysis, it was found to contain 1.116 g of iron and 0.48 g
of oxygen, Find the percentage composition of this compound.
69.92% Fe
30.% O
Empirical formula
3. A compound was analyzed and was found to contain 9.8 g of nitrogen, 0.7 g of hydrogen, and 33.6 g of
oxygen. What is the empirical formula of the compound?
HNO3
Molecular formula
4. A certain sugar has a chemical composition of 40% carbon, 6.6 % hydrogen, and 53.3 % oxygen. The molar
mass is 180 g/mol. What is the molecular formula?
C6H12O6
Mass Stoichiometry
5. Oxygen is produced by the reaction of sodium peroxide and water
2Na2O2 (s) + 2H2O (I)------->O2 (g) + 4NaOH(aq)
a. calculate mass of Na2O2 needed to form 6.20g of oxygen. b. How many g of NaOH are produced when 6.20
g of O2 is formed?
a. 30.2 g Na2O2
b. 31.0g NaOH
Theoretical yield / limiting reactant / excess
6. Calculate the theoretical yield of each product, Identify the limiting reactant, and determine the amount of
excess reactant when 20.0 grams of HCI needed reacts with 20.0 grams of Zn?
37.8g ZnCl2
HCl
18.1g Zn
Limiting Reactant
7. Identify the limiting reactant when 6.33g of H2SO4 reacts with 5.92g of NaOH to produce Na 2SO4 and water.
H2SO4
% yield / limiting reactant
8. Determine the % yield for the reaction between 6.92g of K and 4.28g of O2 if 7.36 g of K 2O is produced.
88.3%
K
Molarity
11. What is the molarity of solution prepared by dissolving 5.68 grams of NaOH in enough water to make
400.mL of solution?
.355M NaOH
Molarity – find grams
12. How many grams of HCl are required to prepare 250.mL of a 0.158M solution?
1.44g HCl
Preparing solutions
13. Explain how you would make 800. ml of a 0.450M solution from concentration HCl (12M).
30.mL 12M HCl and 770. mL H2O
Solution Stoichiometry
14. It is found that 10.00cm3 of 0.200mol dm-3 aqueous sodium carbonate requires 25.00cm3 of hydrochloric acid
to just neutralise it. What is the concentration of the hydrochloric acid?
.16M HCl
Titration
15. A 25 mL sample of HCl was titrated to the endpoint with 15.0mL of 2.0 M NaOH. JWhat was the Molarity
of HCl
1.2 M HCl
16. 10.0mL of H2SO4 was exactly neutralized by 13.5mL of 1.0M KOH. What is the molarity of the H2SO4?
What is the Normality?
Back Titration Stoichiometry
17. 2.04g of an insoluble, dibasic organic acid were dissolved in 20.0cm3 of 2.00 mol dm-3 aqueous sodium
hydroxide. The excess alkali required 17.6cm3 of .50 mol dm-3 hydrochloric acid to neutralize it. What is the
molar mass of the acid?
131 g/mol