Ch 2 Practice Problems
1. According to the law of definite proportions,
A) if the same two elements form two different compounds, they do so in the same ratio.
B) it is not possible for the same two elements to form more than one compound.
C) the ratio of the masses of the elements in a compound is always the same.
D) the total mass after a chemical change is the same as before the change.
2. Which of the following pairs of compounds can be used to illustrate the law of multiple proportions?
A) NH
3
and NCl
3
B) ZnO and ZnCl
2
C) H
2
O and HI
D) NO and NO
2
E) CH
4
and CO
2
3. How many of the following did Dalton not discuss in his atomic theory? I. isotopes II. ions III. protons IV. neutrons V. electrons
A) 1
B) 2
C) 3
D) 4
E) 5
4. When 3.0 L of hydrogen gas (H
2
) reacts with 1.0 L of nitrogen gas (N
2
), 2.0 L of gaseous product is formed.
All volumes of gases are measured at the same temperature and pressure. What is the formula of the product?
A) N
3
H
B) NH
3
C) NH
4
D) NH
E) N
2
H
3
5. Which one of the following statements about atomic structure is false?
A) The electrons occupy a very large volume compared to the nucleus.
B) Almost all of the mass of the atom is concentrated in the nucleus.
C) The protons and neutrons in the nucleus are very tightly packed.
D) The number of protons and the number of neutrons are always the same in the neutral atom.
6. Which of the experiments listed below did not provide the information stated about the nature of the atom?
A) The Rutherford experiment proved that the Thomson "plum pudding" model of the atom was essentially correct.
B) The Rutherford experiment determined the charge on the nucleus.
C) Millikan's oil-drop experiment showed that the charge on any particle was a simple multiple of the charge on the electron.
D) The cathode-ray tube proved that electrons have a negative charge.
7. Which of the following atomic symbols is incorrect?
A)
B)
C)
D)
E)
20
10
Ne
32
16
S
28
14
Si
40
20
Ca
12
8
C
8. The element rhenium (Re) exists as two stable isotopes and 18 unstable isotopes. Rhenium-185 has in its nucleus
A) 75 protons, 75 neutrons.
B) 75 protons, 130 neutrons.
C) 130 protons, 75 neutrons.
D) 75 protons, 110 neutrons.
E) not enough information is given.
9. Which of the following statements is(are) true?

I. O and F have the same number of neutrons.
II. C and N are isotopes of each other because their mass numbers are the same.
III. O 2– has the same number of electrons as Ne.
A) I only
B) II only
C) III only
D) I and II only
E) I and III only
10. Which among the following represent a set of isotopes? Atomic nuclei containing
I. 20 protons and 20 neutrons.
II. 21 protons and 19 neutrons.
III. 22 neutrons and 18 protons.
IV. 20 protons and 22 neutrons.
V. 21 protons and 20 neutrons.
A) I, II, III
B) III, IV
C) I, V
D) I, IV and II, V
E) No isotopes are indicated.
11. How many protons, neutrons, and electrons does the atom 33 S have?
A) 16 protons, 16 neutrons, 33 electrons
B) 17 protons, 17 neutrons, 16 electrons
C) 16 protons, 16 neutrons, 16 electrons
D) 17 protons, 16 neutrons, 17 electrons
E) 16 protons, 17 neutrons, 16 electrons
12. An ion is formed
I. by either adding protons to or subtracting protons from the atom.
II.
III. by either adding electrons to or subtracting electrons from the atom. by either adding neutrons to or subtracting neutrons from the atom.
A) Only I is true.
B) Only II is true.
C) Only III is true.
D) All of the statements are true.
E) Two of the statements are true.
13. Which is the symbol for the isotope of nitrogen that has 7 protons and 8 neutrons?
A) 7
8
N
B)
C)
D)
8
7
N
15
7
N
7
15
N

14. Which of the following represents a pair of isotopes?
A)
B)
C)
14
6
C, 14
7
N
1
1
H, 2
1
H
14
7
N, 15
8
O
D) C, C
60
E) 31
15
P, 31
15
P 3-
15. Which of the following statements is(are) true?
I. The number of protons is the same for all neutral atoms of an element.
II.
III.
The number of electrons is the same for all neutral atoms of an element.
The number of neutrons is the same for all neutral atoms of an element.
A) I, II, and III are all true.
B) Only I and II are true.
C) Only II and III are true.
D) Only I and III are true.
E) I, II, and III are all false.
16. The ion 14 N 3 has
A) 7 protons, 7 neutrons, 7 electrons
B) 7 protons, 7 neutrons, 4 electrons
C) 7 protons, 7 neutrons, 3 electrons
D) 7 protons, 7 neutrons, 10 electrons
E) 7 protons, 14 neutrons, 7 electrons
17. The ion 127 I has
A) 53 protons, 74 neutrons, 54 electrons
B) 53 protons, 74 neutrons, 53 electrons
C) 53 protons, 74 neutrons, 52 electrons
D) 53 protons, 127 neutrons, 54 electrons
E) 53 protons, 53 neutrons, 53 electrons
18. An element's most stable ion forms an ionic compound with chlorine having the formula XCl
2
. If the mass number of the ion is 40 and it has 18 electrons, what is the element and how many neutrons does it have?
A) Ar, 22 neutrons
B) Ar, 24 neutrons
C) S, 24 neutrons
D) Ca, 20 neutrons
E) K, 19 neutrons
19. Which element does not belong to the family or classification indicated?
A) I, halogen
B) Kr, noble gas
C) Co, transition metal
D) K, alkali metal
E) As, lanthanides
20. Which are alkaline earth halides?
A) NaI, KBr, LiF
B) CaF
2
, MgBr
2
, SrI
2
C) PbI
2
, PbBr
2
, CdF
2
D) MgO, MgS, CaO
E) Al
2
O
3
, In
2
O
3
, Ga
2
S
3
21. Select the group of symbols that would correctly complete the following statements, respectively.
___ is the heaviest noble gas.

___ is the transition metal that has 24 electrons as a 3+ ion.
___ is the halogen in the third period.
___ is the alkaline earth metal that has 18 electrons as a stable ion.
A) Rn, Cr, Br, Ca
B) Ra, Co, Cl, K
C) Rn, Co, Cl, Ca
D) Ra, Sc, Br, K
22. ______ form ions with a 2+ charge when they react with nonmetals.
A) Alkali metals
B) Alkaline earth metals
C) Halogens
D) Noble gases
E) None of these choices
23. Which of the following formulas is not correct?
A) MgSO
3
B) Ba(NO
3
)
2
C) NaS
D) KCl
E) NH
4
I
24. Which of the following is not the correct chemical formula for the compound named?
A)
NaOH sodium hydroxide
B)
Fe
3
SO
4
C)
HCl iron(III) sulfate hydrogen chloride
D)
CaBr
2
E)
Mg
3
N
2 calcium bromide magnesium nitride
25. Which of the following is not the correct name for the formula given?
A)
Fe
2
O
3 iron(III) oxide
B)
PBr
5 phosphorus pentabromide
C)
CoO cobalt(II) oxide

D)
CaSO
4
E)
HClO calcium sulfite hypochlorous acid
26. Which is not the correct chemical formula for the compound named?
A) lithium phosphate Li
3
PO
4
B) copper(II) oxide
C) magnesium carbonate
CuO
MgCO
3
D) ammonium sulfide
E) barium nitrate
NH
4
S
Ba(NO
3
)
2
27. What is the correct formula for aluminum carbonate?
A) AlCO
3
B) Al
2
(CO
3
)
3
C) Al
3
(CO
3
)
2
D) Al
2
CO
3
E) Al
3
CO
3
28. Which of the following is not the correct chemical formula for the compound named?
A)
Li
2
O lithium oxide
B)
Fe
3
PO
4
C)
HF iron(III) phosphate hydrogen fluoride
D)
BaCl
2
E)
Mg
3
N
2 barium chloride magnesium oxide

29. Which formula is not correct?
A) NH
4
C
2
H
3
O
2
B) CaO
C) Ba(NO
3
)
2
D) ZnBr
E) NaF
30. What is the correct formula for chromium(VI) oxide?
A) CrO
6
B) Cr
6
O
C) CrO
3
D) Cr
2
O
3
E) CrO
2
31. Which of the following is not the correct name for the formula given?
A)
Fe
2
O
3 iron(III) oxide
B)
PCl
5
C)
CoO phosphorus pentachoride cobalt(II) oxide
D)
BaSO
3
E)
HClO barium sulfate hypochlorous acid
32. Which of the following is not the correct chemical formula for the compound named?
A)
Al(OH)
2 aluminum hydroxide
B)
LiSCN
C)
Fe
2
O
3
D)
BaS
E)
Mg(C
2
H
3
O
2
)
2 lithium thiocyanate iron(III) oxide barium sulfide magnesium acetate

33. Which is the correct formula for copper(I) sulfide?
A) CuS
B) Cu
2
S
C) CuS
2
D) Cu
2
S
2
E) Cu
2
S
3
34. Complete the following table.
Symbol Number of
Protons
Number of
Neutrons
Number of
Electrons
Net Charge
206
82
Pb
3+ 31
52
38
75 54
54
25
Mn
2+ 29 2+
35. Complete the following table.
Symbol
Number of protons
Number of neutrons
Number of electrons
Atomic number
Mass number
Net charge
Name the following compounds:
36. Al
2
(SO
4
)
3
37. NH
4
NO
3
38. NaH
39. K
2
Cr
2
O
7
40. CCl
4
41. AgCl
42. CaSO
4
43. HNO
3
44. N
2
O
3
45. SnI
2
Write the formula for:
56 Fe 2+
35
45
1-

46. sodium dichromate
47. iron(III) oxide
48. dinitrogen trioxide
49. cobalt(II) chloride
50. aluminum hydroxide
51. hydrosulfuric acid
52. sulfurous acid
53. nitric acid
54. phosphoric acid
55. acetic acid
56. Write the chemical formulas for the following compounds or ions. a) nitrate ion _________________ b) aluminum oxide c) ammonium ion d) perchloric acid
_________________
_________________
_________________ e) copper(II) bromide _________________
57. Write the names of the following compounds: a) FeSO
4
__________________________________________ b) NaC
2
H
3
O
2
__________________________________________
__________________________________________ c) KNO
2 d) Ca(OH)
2
__________________________________________ e) NiCO
3
__________________________________________

Answers
1. C 11. E 21. C 31. D
2. D 12. B 22. B 32. A
3. E 13. C 23. C 33. B
4. B 14. B 24. B
5. D 15. B 25. D
6. A 16. D 26. D
7. E 17. A 27. B
8. D 18. D 28. B
9. C 19. E 29. D
10. D 20. B 30. C
34.
Symbol Number of Number of Number of
Protons Neutrons Electrons
Net Charge
206
82
Pb
82 124 82 0
69
31
Ga 3+ 31 38 28 3+
127
52
Te
252 75 54 2–
54
25
Mn 2+ 25 29 23 2+
35.
Symbol 56 Fe 2+
Number of protons
Number of neutrons
Number of electrons
Atomic number
Mass number
Net charge
36. aluminum sulfate
37. ammonium nitrate
38. sodium hydride
39. potassium dichromate
40. carbon tetrachloride
41. silver chloride
42. calcium sulfate
26
30
24
26
56
2+
80 Br-
35
45
36
35
80
1-

43. nitric acid
44. dinitrogen trioxide
45. tin(II) iodide
46. Na
2
Cr
2
O
7
47. Fe
2
O
3
48. N
2
O
3
49. CoCl
2
50. Al(OH)
3
51. H
2
S
52. H
2
SO
3
53. HNO
3
54. H
3
PO
4
55. HC
2
H
3
O
2
56. a. NO
3
–
b. Al
2
O
3
c. NH
4
+ d. HClO
4
e. CuBr
2
57. a. iron(II) sulfate b. sodium acetate c. potassium nitrite d. calcium hydroxide e. nickel(II) carbonate