Ch3 Practice Test

MULTIPLE CHOICE

Section 3.1 Balancing Chemical Equations

1. What is the sum of the coefficients when the following equation is balanced using the lowest, whole numbered coefficients?

_____ B₂O₃(s) + _____ HF(l) ---> ____ BF₃(g) + _____ H₂O(l)
a) 8
b) 11
c) 15
d) none of these

2. Aluminum metal reacts with iron(II) sulfide to form aluminum sulfide and iron metal. What is the coefficient for aluminum when the equation is balanced using the lowest, whole-numbered coefficients?
a) 1
b) 2
c) 3
d) 4

Section 3.3 Avogadro's Number and the Mole

3. How many grams does a single chlorine molecule, Cl₂, weigh?
a) 5.887 x 10^-23 g
b) 1.177 x 10^-22g
c) 35.45 g
d) 70.90 g

4. How many molecules are there in 5.00 g of FeSO₄?
a) 5.46 x 10^-26 molecules
b) 1.98 x 10²²molecules
c) 1.83 x 10²⁵ molecules
d) 4.58 x 10²⁶ molecules

5. What is the identity of substance X if 0.380 mol of X weighs 17.5 g?
a) NO₂
b) NO₃
c) N₂O
d) N₂O₄

Section 3.4 Stoichiometry: Chemical Arithmetic

6. Dinitrogen monoxide gas decomposes to form nitrogen gas and oxygen gas. How many grams of oxygen are formed when 5.00 g of dinitrogen monoxide decomposes?
a) 0.909 g
b) 1.82 g
c) 3.64 g
d) 7.27 g

Section 3.5 Yields of Chemical Reactions

7. If the percent yield is 75% and 45 g of NO₂ are used in the following reaction, how many grams of nitric acid are produced?

3 NO₂(g) + H₂O(l) ---> 2 HNO₃(aq) + NO(g)
a) 30.8 g
b) 41.1 g
c) 54.8 g
d) 69.3 g

Section 3.6 Reactions with Limiting Amounts of Reactants

8. Which substance is the limiting reagent when 2.0 g of sulfur reacts with 3.0 g of oxygen and 4.0 g of sodium hydroxide according to the following reaction:

2 S(s) + 3 O₂(g) + 4 NaOH(aq) ---> 2 Na₂SO₄(aq) + 2 H₂O(l)
a) S
b) O₂
c) NaOH
d) all react equally

Section 3.7 Concentrations of Reactants in Solution: Molarity

9. A solution is 0.540 M NaOH. What volume contains 15.5 g of NaOH?
a) 0.202 L
b) 0.718 L
c) 1.15 L
d) 1.40 L

10. What is the concentration of an AlCl₃ solution if 150. mL of solution contains 250. mg of Cl^- ion?
a) 1.57 x 10^-2M
b) 3.75 x 10^-4 M
c) 4.70 x 10^-4 M
d) 1.41 x 10^-3 M

Section 3.8 Diluting Concentrated Solutions

11. A student prepared a stock solution by dissolving 20.0 g of KOH in enough water to make 150. mL of solution. He took 15.0 mL of the diluted solution and added another 50.0 mL of deionized water. What is the concentration of the final solution?
a) 0.548 M
b) 0.713 M
c) 1.03 M
d) 1.66 M

Section 3.11 Percent Composition and Empirical Formulas

12. What is the empirical formula for perfluoropropane if the compound contains 81% fluorine and 19% carbon by mass?
a) CF₃
b) C₂F₈
c) C₃F₈
d) C₁₉F₈₁

Section 3.12 Determining Empirical Formulas: Elemental Analysis

13. Combustion analysis of 1.500 g unknown compound containing only carbon and hydrogen produced 4.554 g of CO₂ and 2.322 g of H₂O. What is the empirical formula of the compound?
a) CH₂
b) C₂H₅
c) C₄H₁₀
d) C₅H₂

ANSWERS