CHM 22 Test 2Take-homeKey
Spring 2012
Student Name ____________________ Section ______
Page 1 of 4
Multiple Choice (2 points each)
1. The Law of Definite Composition states that
A. a compound always contains one element physically combined in variable proportions by
mass.
B. a compound always contains one element chemically combined in a definite proportion
by mass.
C. a compound always contains two or more elements physically combined in variable
proportions by mass.
D. a compound always contains two or more elements chemically combined in a definite
proportion by mass.
Answer: D; Difficulty: easy; Reference: Section 5.3
2. Which pair of formulas illustrates the Law of Multiple Proportions?
A. CH3Cl and CH3OH
B. H2O and HOH
C. CuCl2 and CuBr
D. H2O and H2O2
Answer: D; Difficulty: easy; Reference: Section 5.3
3. Let Z represent atomic number, A represent mass number, and N represent the number of
neutrons in an atom. Which of the following is correct?
A. N = A + Z
B. Z = A + N
C. N = A - Z
D. A = N - Z
Answer: C; Difficulty: easy; Reference: Section 5.8
4. The elements in group 6A form ions with a charge of
A. +6
B. +2
C. -6
D. -2
Answer:D; Difficulty: easy; Reference: Section 6.2
5. What is the formula for the compound that forms between the elements calcium and fluorine?
A. CaF
B. CaF2
C. Ca2F
D. Ca2F2
Answer:B; Difficulty: easy; Reference: Section 6.4
6. How many moles are present in 3.01 1023 molecules of CH4?
A. 48.0
B. 0.500
C. 8.00
D. 2.00
Answer: B; Difficulty: easy; Reference: Section 7.1
CHM 22 Test 2Take-homeKey
Spring 2012
Student Name ____________________ Section ______
Page 2 of 4
7. What is the molar mass of KClO3?
A. 90.55g
B. 122.55g
C. 161.45g
D. 6.02 1023 g
Answer: B; Difficulty: easy; Reference: Section 7.2
8. What is the percent by mass of carbon in carbon dioxide?
A. 3.66%
B. 366%
C. 27.28%
D. 42.9%
Answer: C; Difficulty: easy; Reference: Section 7.3
9. The following reaction: Mg + FeO MgO + Fe, is an example of
A. combination.
B. cecomposition.
C. single-displacement.
D. double-displacement.
Answer: C; Difficulty: easy; Reference: Section 8.4
10. The following reaction: NaOH + HCl NaCl + H2O, is an example of
A. combination.
B. decomposition.
C. single-displacement.
D. double-displacement.
Answer: D; Difficulty: easy; Reference: Section 8.4
11. The following reaction: K + NaBr KBr + Na, is an example of
A. combination.
B. decomposition.
C. single-displacement.
D. double-displacement.
Answer: C; Difficulty: easy; Reference: Section 8.4
12. The reaction: N2 + O2 + 182.6 kJ 2NO, is
A. endothermic.
B. exothermic.
C. isothermic.
D. protothermic.
Answer: A; Difficulty: easy; Reference: Section 8.5
13. In the expression, 3CaBr2,
A. 2 and 3 are subscripts
B. 2 and 3 are coefficients
C. 2 is a subscript and 3 is a coefficient
D. 3 is a subscript and 2 is a coefficient
Answer: C; Difficulty: easy; Reference: Section 8.1
CHM 22 Test 2Take-homeKey
Spring 2012
Student Name ____________________ Section ______
Page 3 of 4
14. Given the reaction: 4NH3 + 3O2 2N2 + 6H2O. How many moles of N2 are produced when
1.0 mole of NH3 is consumed?
A. 0.50
B. 1.0
C. 2.0
D. 4.0
Answer: A; Difficulty: easy; Reference: Section 8.3
15. A combustion reaction will always involve the release of
A. sound.
B. heat.
C. oxygen gas.
D. steam.
Answer: B; Difficulty: easy; Reference: Section 8.4
Write out your answers to the following questions in the space provided. Write neatly and
legibly. (4 points each)
16. How are the different isotopes of an element alike; how are they different?
Answer: All isotopes of an element always have the same number of protons or atomic number.
The difference between various isotopes of an element is that they have different numbers of
neutrons and different mass numbers.;Difficulty: easy; Reference: Section 5.8
17. A compound is composed of 24.27% carbon, 4.08% hydrogen, and 71.65% chlorine. The
compound has a molar mass of 98.96g.
A. What is the empirical formula of the compound?
B. What is the molecular formula of the compound?
Answer: A. The empirical formula is CH2Cl; B. The molecular formula is C2H4Cl2; Difficulty:
medium; Reference: Section 7.6
18. Change these word equations into balanced chemical equations.
A. Carbon plus oxygen yields carbon monoxide.
B. Sodium chlorate decomposes to form sodium chloride and oxygen.
C. Phosphoric acid and potassium hydroxide yields potassium phosphate and water.
D. Fluorine and potassium bromide yields potassium fluoride and bromine.
CHM 22 Test 2Take-homeKey
Spring 2012
Student Name ____________________ Section ______
Page 4 of 4
Answer: A. 2C + O2 2CO; B. 2NaClO3 2NaCl + 3O2; C. H3PO4 + 3KOH
3HOH; D. F2 + 2KBr 2KF + Br2; Difficulty: medium; Reference: Section 8.2
K3PO4 +
19. The following questions refer to a reaction in which sodium and water react to produce
sodium hydroxide and hydrogen gas.
A. Write a balanced chemical equation for the reaction.
B. When one mole of hydrogen is produced, how many moles of sodium are consumed?
C. When one mole of hydrogen is produced, how many moles of water are consumed?
D. When one mole of hydrogen is produced, how many moles of sodium hydroxide are
produced?
Answer: A. 2Na + 2HOH 2NaOH + H2; B. 2 moles of sodium are consumed; C. 2 moles of
water are consumed; D. 2 moles of sodium hydroxide are produced; Difficulty: medium;
Reference: Section 8.2
20. The following questions refer to a reaction in which calcium bromide and silver nitrate
react to produce calcium nitrate and silver bromide.
A. Write a balanced chemical equation for the reaction.
B. When one mole of calcium bromide is consumed, how many moles of silver nitrate are
consumed?
C. When one mole of calcium bromide is consumed, how many moles of calcium nitrate are
produced?
D. When one mole of calcium bromide is consumed, how many moles of silver bromide are
produced?
Answer: A. CaBr2 + 2AgNO3 Ca(NO3)2 + 2AgBr; B. 2 moles of silver nitrate are consumed;
C. 1 mole of calcium nitrate is produced; D. 2 moles of silver bromide are produced; Difficulty:
medium; Reference: Section 8.2