Unit 4: Chemical Quantities Review
Nov 2013
Instructions: This review is intended to prepare you for the problem solving
(application/communication) section of the test. You should be able to complete this section of the
test in 45 minutes.
Communication
Criteria
Formula provided
Significant digit rules obeyed
Never
0
0
Rarely
1
1
Sometimes
2
2
Frequently
3
3
Always
4
4
Units provided
0
1
2
3
4
1.
Copper (II) hydroxide, Cu(OH)2, is found in nature as the mineral spertiniite. Copper (II) hydroxide
can be reacted to produce copper metal, the material that makes everything from roofing
materials to wiring.
a) Calculate the percent composition of copper (II) hydroxide. [A 3]
b) What mass of copper can be produced from 1 tonne (1000 kg) of spertiniite? [ A 1]
2.
The combustion of 3.42 g of a compound known to contain only nitrogen and hydrogen gave
9.23 g of NO2 and 5.43 g of H2O. What is the empirical formula of this compound? [5 A]
3.
Using a mass spectrometer it was determined the molar mass of a certain hydrocarbon known
as “chrysene” is 228.3 g/mol. If the empirical formula of the compound was C3H2, what is the
molecular formula? [2 A]
4.
When 27.40 g of hydrated cobalt (II) chloride undergoes hydrate analysis, 14.94 g of anhydrous
CoCl2 are formed. Calculate the chemical formula of the hydrate. [3 A]
5.
In the textile industry, chlorine is used to bleach fabrics. Any of the toxic chlorine that remains
after the bleaching process is destroyed by reacting it with a sodium thiosulfate solution,
Na2S2O3 (aq). What mass of Na2S2O3 must be added to destroy 25 kg of chlorine, assuming
excess water is present. [3 A]
Na2S2O3 (aq) + 4Cl2(g) + 5H2O (l)  2NaHSO4(aq) + 8HCl (aq)
6.
A 56.5 g sample of magnesium hydroxide (Mg(OH)2 (s)) was reacted with 45.0 g of hydrochloric
acid (HCl (aq)) to form magnesium chloride and water.
a) Write the balanced chemical equation. [1 A]
b) Calculate the theoretical yield of MgCl2 produced in the reaction. [5 A]
c) How many grams of the excess reactant will remain after the reaction? [2 A]