# Sample Questions - Chemical Calculations

## Department of Chemistry

### Sample Questions - Chemical Calculations

FIRST YEAR CHEMISTRY

Assessment Test

Sample Questions, Chemical Calculations

1. Find the mass percentage of iron in Fe 2 O 3 . Atomic weights: Fe 55.8, O 16.0.

2. What is the molar mass of SrCl2 . 6H2O? Include the correct units in your answer. Atomic weights: Sr 87.6, Cl 35.5, H 1.01, O 16.0.

3. How many moles of oxygen are required to react with 12.0 grams of carbon to produce carbon monoxide? Atomic weights: C 12.0, O 16.0. The balanced equation is

2 C + O2   --> 2 CO

4. How many moles of NaOH are required to react with the SO2   produced by the oxidation of 0.500 moles of FeS2? The balanced equations are

4 FeS2   + 11 O2   --> 2 Fe2O3   + 8 SO2

SO2   + 2 NaOH --> Na2SO3   + H2O

5. A compound of sulfur and fluorine contains 29.7% S and 70.3% F (percentages are by mass). What is the empirical formula of the compound?

6. (a) How many grams of AlCl3   can be produced when 0.100 moles of aluminum reacts with excess chlorine? Atomic weights: Al 27.0, Cl 35.5. The balanced equation is

2 Al + 3 Cl2   --> 2 AlCl3 (b) What is the % yield of this reaction if 12.5 grams of AlCl3   are actually obtained? 7. What is the molarity of a copper(II) chloride solution if 10.0 grams of CuCl 2   are dissolved in water to give 250.0 mL of solution? The molar mass of CuCl 2   is 134.5 g/mol.

8. What is the molarity of a sodium hydroxide solution if 50.0 mL of the solution requires 38.6 mL of 0.0976 M HCl for titration?

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Last revised: Aug. 16th, 2006 by A. van der Est

Dept. of Chemistry
Brock University
1812 Sir Isaac Brock Way
St. Catharines, ON