Name:    Balancing & Stoichiometry

Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.

1.

The combustion of propane produces carbon dioxide and steam.

C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g)

All of the following statements concerning this reaction are correct EXCEPT
 a. three molecule of carbon dioxide are formed per one molecule of propane consumed. b. five molecules of oxygen are consumed per one molecule of propane consumed. c. four moles of steam are formed per five moles of oxygen consumed. d. the combined mass of reactants consumed equals the mass of products formed. e. three grams of carbon dioxide are formed per five grams of oxygen consumed.

2.

Ammonia is prepared by reacting nitrogen and hydrogen gases at high temperature according to the unbalanced chemical equation below.

__ N2(g) + __ H2(g) → __ NH3(g)

What are the respective coefficients when the equation is balanced with the smallest whole numbers?
 a. 1, 1, 1 b. 1, 3, 1 c. 1, 3, 2 d. 2, 1, 2 e. 2, 3, 2

3.

The products of the complete combustion of a hydrocarbon are carbon dioxide and water. Write a balanced chemical equation for the combustion of pentane, C5H12.
 a. C5H12(g) + 8 O2(g) → 5 CO2(g) + 6 H2O(g) b. C5H12(g) → 5 C(s) + 6 H2(g) c. C5H12(g) + 9 O2(g) → 4 CO2(g) + 5 H2O(g) d. C5H12(g) + 11 O2(g) → C5O10(g) + 6 H2O(g) e. C5H12(g) + 11 O2(g) → 5 CO2(g) + 12 H2O(g)

4.

Aluminum reacts with oxygen to produce aluminum oxide.

4 Al(s) + 3 O2(g) → 2 Al2O3(s)

If 5.0 moles of Al react with excess O2, how many moles of Al2O3 can be formed?
 a. 1.0 mol b. 2.0 mol c. 2.5 mol d. 5.0 mol e. 10.0 mol

5.

The complete combustion of 0.40 moles of butane gas, C4H10, will
 a. consume 0.40 mol O2 and produce 0.20 mol CO2. b. consume 0.80 mol O2 and produce 0.40 mol CO2. c. consume 1.3 mol O2 and produce 0.80 mol CO2. d. consume 2.6 mol O2 and produce 1.6 mol CO2. e. consume 5.2 mol O2 and produce 3.2 mol CO2.

6.

What mass of oxygen is consumed by the complete combustion of 23.0 grams of ethylene?

C2H4(g) + 3 O2(g) → 2 CO2(g) + 2 H2O(g)
 a. 8.75 g b. 26.2 g c. 60.5 g d. 69.0 g e. 78.7 g

7.

What is a correct method for determining how many grams of oxygen react with 1.00 gram of pentane?

C5H12(g) + 8 O2(g) → 5 CO2(g) + 6 H2O(g)
 a. 1.00 g C5H12 = b. 1.00 g C5H12 = c. 1.00 g C5H12 = d. 1.00 g C5H12 = e. 1.00 g C5H12 =

8.

What is a correct method for determining how many moles of calcium oxide are produced in the reaction of 10.0 g calcium with excess oxygen?

2 Ca(s) + O2(g) → 2 CaO(s)
 a. 10.0 g Ca = b. 10.0 g Ca = c. 10.0 g Ca = d. 10.0 g Ca = e. 10.0 g Ca =

9.

Polyethylene is a polymer consisting of only carbon and hydrogen. If 3.000 g of the polymer is burned in oxygen it produces 3.855 g H2O and 9.414 g CO2. What is the empirical formula for polyethylene?
 a. CH2 b. C2H c. C2H3 d. C5H8 e. C7H8

10.

Cyclohexene, a hydrocarbon, has a molar mass of 82.1 g/mole. If the combustion of 0.8300 g cyclohexene produces 0.9102 g H2O and 2.668 g CO2, what is the molecular formula of this compound?
 a. C3H5 b. C5H22 c. C6H10 d. C6H14 e. C7H10

11.

A reaction which forms a solid product is an example of a(n)________.
 a. oxidation-reduction reaction b. combustion reaction c. precipitation reaction d. gas evolution reaction e. none of the above

12.

Which of the following statements about balancing reactions is FALSE?
 a. If there is no coefficient or subscript, a one is implied. b. By adding a coefficient, we change the properties of the compound in a chemical reaction. c. Subscripts are multiplied by the coefficients to determine the number of atoms in a compound. d. Coefficients are added to compounds to ensure both sides of the reaction have equal numbers of each atom. e. All of the above statements are true.

13.

Before a chemical equation can be written, one must know
 a. the atomic mass of all the elements involved. b. the molar mass of all the compounds. c. the symbols and formulas of all reactants and products. d. the symbols and formulas of all reactants and products. e. none of the above.

14.

When the equation,  ___N2  +  ___H2  →  ___NH3 is balanced, the coefficient of hydrogen is
 a. 1 b. 2 c. 3 d. 4 e. none of the above

15.

What are the coefficients for the following reaction when it is properly balanced?

___CH4 + ___O2  →  ___CO2 + ___H2O
 a. 2, 1, 3, 1 b. 1, 3, 2, 1 c. 2, 3, 2, 2 d. 1, 2, 1, 2 e. none of the above

16.

How many moles of water are made from the reaction of 2.2 moles of oxygen gas?
Given the reaction:  2H2 + O2 → 2H2O
 a. 4.4 mol H2O b. 2.2 mol H2O c. 1.1 mol H2O d. 3.3 mol H2O e. not enough information

17.

How many moles of chlorine gas are needed to make 0.6 moles of sodium chloride?
Given the reaction:  2Na + Cl2 ? 2NaCl
 a. 0.6 mol NaCl b. 0.3 mol NaCl c. 1.2 mol NaCl d. 3.6 mol NaCl e. not enough information

18.

How many grams of water are made from the reaction of 16.0 grams of oxygen gas?
Given the reaction:  2H2 + O2 → 2H2O
 a. 9.00 g b. 16.0 g c. 18.0 g d. 36.0 g e. not enough information

19.

How many grams of chlorine gas are needed to make 117 grams of sodium chloride?
Given the reaction:  2Na + Cl2 → 2NaCl
 a. 35.5 g Cl2 b. 71.0 g Cl2 c. 48.2 g Cl2 d. 142 g Cl2 e. not enough information

20.

How many grams of sodium metal are needed to make 29.3 grams of sodium chloride?
Given the reaction:  2Na + Cl2 → 2NaCl
 a. 46.0 g Na b. 23.0 g Na c. 11.5 g Na d. 5.75 g Na e. not enough information