1. Week A balanced chemical equation has equal numbers of atoms of each type on both sides of the equation. This illustrates the principle of
Conservation of energy C. Action and reaction
Conservation of mass D. Natural selection
2. Consider the following chemical equation: 3HfCl3 + Al  3HfCl2 + AlCl3 What are the reactants in this equation?
HfCl3 and AlCl3
HfCl3 and Al
HfCl2 and Al
Al and AlCl3

2. 3. An unbalanced chemical equation is shown below
3. An unbalanced chemical equation is shown below. __ H3BO3  __ B2O3 + __ H2O What are the coefficients of the balanced equation?
2: 1: 3 c. 3: 1: 2
2: 2: 3 d. 3: 2: 2
4. Aluminum oxide decomposes to produce aluminum plus oxygen gas. Identify the balanced equation for this decomposition reaction.
Al2O3  2Al + 3O
Al2O3  2Al + 3O2
2Al2O3  4Al + 3O2
4Al + 3O2  2Al2O3

3. 6. The formula for dinitrogen tetraoxide is
5. Rust forms by the reaction of iron with oxygen to produce iron oxide. An 88 g iron nail rusted. The rusted nail (iron oxide) had a mass of 102 g. Identify the mass of oxygen that reacted in the rusting of the nail
14 g
88 g
102 g
200 g
6. The formula for dinitrogen tetraoxide is
N3O3 NO
N2O2
N2O4

4. 7. What are the coefficients that will balance the skeleton equation below? AlCl3 + NaOH  Al(OH) 3 + NaCl
1,3,1,3 c. 1,1,1,3
3,1,3,1 d. 1,3,3,1
8. Which of the following is a balanced equation representing the decomposition of lead(IV) oxide?
a. PbO2  Pb + 2O
b. PbO2  Pb + O2
c. Pb2O  2Pb + O
d. PbO  Pb + O2

5. 15 grams C. 45 grams 30 grams D. 74 grams
9. During science lab, Mr. V's students tested the reactivity of various metals in sulfuric acid. When zinc was added to sulfuric acid, bubbles were produced, a sure sign that a chemical reaction had taken place. Based on the law of conservation of matter, if 30 grams of zinc are added to 45 grams of sulfuric acid to produce just 1 gram of hydrogen gas, how much zinc sulfate would also be produced? The formula for the chemical reaction is as follows: Zn + H2SO4 ZnSO4 + H2
15 grams C. 45 grams
30 grams D. 74 grams
10. Classify the following reaction:
CaCO3 (s)  CaO (s) + CO2 (g)
Neutralization
Synthesis
Displacement
Decomposition