Download 1. Balance the following equation. What is the sum of the coefficients

1. Balance the following equation. What is the sum of the coefficients of the reactants and
products?
1
Fe2O3(s)
a) 5
b) 6
+ _3__ C(s) →
c) 7
2
Fe(s) + _3__ CO(g)
d) 8
e) 9
2. Which of the following equations represents an acid-base neutralization reaction?
a) H2SO4 + Zn → ZnSO4 + H2
b) NaOH + HClO3 → NaClO3 + H2O
c) K2SO4 + Ba(OH)2 → BaSO4 + 2KOH
d) HCl + AgNO3 → HNO3 + AgCl
e) WO3 + 3 H2 → W + 3 H2O
3. What is the oxidation number for nitrogen in KNO2?
a) -1
b) -3
c) +3
d) +5
+1 + #N +2(-2) = 0
#N = +3
e) -5
4. Identify the oxidizing agent in the following oxidation-reduction reaction.
Ag+ reduced to Ag
Cu reducing agent
2 AgNO3(aq) + Cu(s) →
Cu(NO3)2(aq) + 2 Ag(s)
Cu oxidized to Cu2+
(+1)
(0)
(+2)
(0)
Ag+ oxidizing agent
a) Ag+
b) NO3-
d) Cu2+
c) Cu
e) Ag
5. To three significant figures, what is the percent of sulfur in Al2(SO4)3?
(F.W. Al2(SO4)3 = 342.17 amu)
a) 28.1
b) 84.2
c) 45.3
d) 38.9
e) 9.37
3 sulfur atoms
Al2(SO4)3
3 x 32.07 amu x 100 = 28.1
342.17 amu
6. A hospital patient is given a solution containing 9.00 x 10-9 g of iodine-131 (isotopic
weight: 131). How many atoms of iodine are present? Avogadro’s Number = 6.02 x 1023
a)
b)
c)
d)
e)
6.68 x 1017
1.36 x 108
1.36 x 109
4.14 x 1013
4.14 x 1015
9.00 x 10-9g x 1 mol x 6.02x1023 atoms
131 g
1 mol
1
7. In which of the following pairings of masses does the first listed mass contain more moles of
substance than the second listed mass?
calculate molar masses, then moles of each
a) 18.02 g H2O and 18.02 g NH3
b) 38.5 g CH4 and 38.5 g CO2
c) 44.01 g CO2 and 44.01 g CO
d) more than one correct response
e) no correct response
8. In the following reaction, how many grams of H2O are produced if 6.13 g of N2H4 react?
N2H4 + 3O2 → 2NO2 + 2H2O
M.W. = 18.02
a) 6.89 g
b) 3.45 g
c) 12.3 g
d) 1.72 g
e) 8.96 g
M.W. 32.06
6.13 g x 1 mol x 2 mol H2O x 18.02 g
32.06 g
1 mol N2H4 1 mol
9. How many moles of carbon monoxide will be produced from the reaction of 4.5 moles of
SiO2 and 4.5 moles of carbon? (Hint: one reagent is limiting)
a)
b)
c)
d)
e)
1.5
3.0
4.5
6.0
9.0
+ 3C
→
SiC + 2 CO
SiO2
4.5 moles
4.5 moles
1
3
limiting reagent has lowest mole to coefficient ratio
4.5 moles C x 2 mol CO / 3 mol C = 3.0 mol CO
10. How many moles of nitrate ions are in 78.45 g of Cu(NO3)2? F.W. 187.57 amu
Atomic weights: Cu = 63.55, O = 16.00, N = 14.01
a)
b)
c)
d)
e)
0.2091
0.4182
0.8365
1.673
3.346
78.45 g Cu(NO3)2 x
1 mol Cu(NO3)2
187.57 g Cu(NO3)2
x
2 mol NO3
1 mol Cu(NO3)2
11. The mineral zircon contains 49.8% Zr, 15.3% Si and 34.9% O. What is the empirical
formula? (Atomic weights: Zr = 91.2, Si = 28.1, O = 16.0)
a)
b)
c)
d)
e)
ZrSiO2
ZrSi2O4
Zr2SiO5
ZrSiO4
ZrSiO3
49.8 g Zr = 0.55 mol
15.3 g Si = 0.54 mol
34.9 g O = 2.18 mol
2
0.55/0.54 = 1
0.54/0.54 = 1
2.18/0.54 = 4
12. When a student reacted 17.5 g of MnO2 with excess aluminum and obtained 11.2 g of Al2O3,
what was the % yield? (F.W. MnO2 = 86.9 g/mol; F.W. Al2O3 = 102 g/mol)
3 MnO2 + 4 Al → 2 Al2O3 + 3 Mn
a)
b)
c)
d)
e)
54.5
62.3
78.7
81.8
92.6
17.5 g MnO2 x 1 mol x 2 Al2O3 x 102 g = 13.7 g
86.9 g
3 MnO2
1 mol
theoretical yield
actual yield 11.2 g
x 100
theoretical yield 13.7 g
=
81.8 % yield
13. Which of the following statements concerning evaporation is correct?
a) Molecules with energies below average are those that escape from the liquid.
b) Evaporation is an exothermic process.
c) Increasing the surface area of the liquid decreases the rate of evaporation.
d) Increasing the temperature of the liquid decreases the rate of evaporation.
e) Evaporation causes the temperature of the liquid to decrease.
14. Which conversion of units for pressure is CORRECT?
a)
b)
c)
d)
e)
2.28 x 103mm Hg = 3.51 atm
152 torr = 0.217 atm
114 mm Hg = 0.150 atm
0.0600 atm = 45.6 cm Hg
830 torr = 830 cm Hg
15. Which of the following is an indicator of STRONG intermolecular forces in liquids?
a) Low Heat of Vaporization
b) Low Boiling Point
c) Low Surface Tension
d) Low Vapor Pressure is an indication of Strong intermolecular forces in liquids.
e) None of the above.
16. The pressure on a 14.4 L sample of oxygen at 748 mm Hg is increased to 1.31 x 103 mm Hg
at constant temperature. What will be the new volume in L?
a)
b)
c)
d)
e)
8.22
17.5
12.4
25.2
6.30
V1P1 = V2P2
14.4 L x 748 mm Hg = V2 x 1.31 x 103 mm Hg
3
17. Gas evolved in the fermentation of sugar in wine making occupies a volume of 0.75 L at
20oC at 720 mm Hg. What volume (L) would the gas occupy at 39oC and 1.00 atm?
a)
b)
c)
d)
e)
0.76
0.80
0.73
0.67
0.85
V1P1/T1 = V2P2/T2
0.75 L x 720 mm Hg =
(20 + 273) K
V2 x 760 mm Hg
(39 + 273) K
18. What is the density of chlorine in g/L at STP?
1 mol of any gas = 22.4 L at STP
mass = 2 x 35.45 g/mol Cl2 = 3.2 g/L density
volume
22.4 L/mol
a) 0.80
b) 3.2 c) 1.6 d) 6.4 e) 18.2
19. Which of the following molecules exhibits hydrogen-bonding in the pure liquid?
••
a) CH4
b) Br2
c) NH3 d) H2
e) CH3CH2CH3
All of these molecules, except for NH3, are nonpolar and exhibit only London Forces.
20. Assume 453.6 g of dry ice (solid CO2) is placed in an evacuated 50.0 L closed tank. What
will be the pressure in the tank in atmospheres at a temperature of 45oC? Assume that all
the CO2 has been converted into gas. M.W. CO2 = 44.01; the universal gas constant is
0.0821 L atm mole-1 K-1
n = 453.6 g x 1 mol/44.01 g = 10.31 mol
a) 7.25
b) 6.10
P x V = nRT
c) 10.8
P x 50 L = 10.31 mol x 0.0821 L atm mole-1 K-1 x (45 + 273)K
d) 9.15
e) 5.38
21. Which of the following is NOT a distinguishing characteristic of a gas?
a)
b)
c)
d)
e)
Indefinite shape.
Indefinite volume.
Low density.
Small compressibility.
Moderate thermal expansion.
22. Arrange the following molecules according to increasing strength of intermolecular
CH3CH2OH
CH3CH2CH3
CH4
H2O
attractive forces: NH3
a)
b)
c)
d)
e)
NH3 < CH3CH2OH < CH3CH2CH3 < CH4 < H2O
CH4 < CH3CH2CH3 < NH3 < CH3CH2OH < H2O
NH3 < CH4 < CH3CH2CH3 < CH3CH2OH < H2O
CH3CH2CH3 < CH4 < CH3CH2OH < NH3 < H2O
CH4 < CH3CH2CH3 < NH3 < H2O < CH3CH2OH
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23. What is the partial pressure of oxygen (in atm) a scuba diver experiences at a depth of 75 ft?
Assume that 20 % of the compressed air she is breathing is oxygen and that the pressure of
the water is equal to 1 atm for every 33 ft of depth.
a)
b)
c)
d)
e)
1.2
0.45
0.95
0.65
0.20
Total PT =
Pwater
+
Pair
PT = 75 ft x 1 atm + 1 atm (air) = 3.27 atm
33 ft
20 % of air = PO2 = 3.27 atm x 0.20 = 0.65 atm
24. Which of the following is an exothermic process?
a)
b)
c)
d)
e)
Evaporation
Melting
Sublimation
Boiling
Freezing
25. The compounds CF4 and CCl4 are tetrahedral molecules. Neither is polar. What is the
reason for the large difference in their boiling points of -129oC (CF4) and 76.8oC (CCl4)?
a) CCl4 has higher London Forces due to its larger size and greater number of
electrons; i.e. it has a greater polarizability than CF4.
b) CCl4 has more Hydrogen Bonding.
c) CCl4 has stronger Dipole-Dipole Forces.
d) CF4 has higher London Forces.
e) CF4 has more Hydrogen Bonding.
26. Which of the following statements is NOT correct?
a)
b)
c)
d)
e)
Most solids become more soluble in water with increasing temperature.
Gases become more soluble in water with increasing temperature.
The solubility of a gas increases with increasing pressure.
A supersaturated solution is an unstable solution.
When salts dissolve in water, entropy increases.
27. Based on the generalization of “like dissolves like”, and the solubility rules listed on
page 6, which of the following substances will NOT dissolve in water?
a) KNO3
ionic & soluble
b) CH3CH2OH
polar, H-bonding
c) CH3CH2CH2CH2CH3
d) CaCl2
nonpolar
ionic & soluble
e) NH3
polar, H-bonding
28. For which of the following will the solubility in water increase with increasing pressure?
The solubility for gases increases with increasing pressure.
a) NaCl
b) CCl4
c) alcohol
d) MgCl2
5
e) O2
29. When an aqueous solution of sodium phosphate is mixed with an aqueous solution of iron
(III) nitrate a precipitate is formed. Consult the solubility rules below and identify the
spectator ions for this reaction?
FePO4 (s) is insoluble; precipitation drives the reaction.
a) Na+ and PO43b) Fe3+ and PO43c) Na+ and NO3Na+ and NO3- are soluble and do not react = spectator ions
3+
d) Fe and NO3
e) none are spectator ions
30. Based on the solubility rules below, what will happen when aqueous solutions of CsBr and
Ba(NO3)2 are mixed together?
a)
b)
c)
d)
e)
Barium bromide will precipitate.
Cesium nitrate will precipitate.
Barium nitrate will precipitate.
Cesium bromide will precipitate.
No reaction occurs because all combinations of these ions are soluble.
Solubility Rules of Common Ionic Compounds
•
•
•
•
•
•
•
All ionic compounds of Li, Na, K, Rb, Ce, and ammonium ions are soluble.
All nitrates, chlorates, and perchlorates are soluble.
The chlorides, bromides, and iodides of most metals are soluble. Principal exceptions
are those of lead, silver, and mercury (I). Barium & cesium bromide are soluble (not an
exception).
All sulfates are soluble except those of strontium, barium, lead, and mercury (I).
All carbonates, chromates, and phosphates are insoluble except those of lithium,
sodium, potassium, rubidium, cesium, and ammonium.
The hydroxides of Li+, Na+, K+, Rb+, Ce+ are soluble. The hydroxides of Ca2+, Sr2+, and Ba2+
are moderately soluble. The rest of the hydroxides are insoluble.
The sulfides of all metals are insoluble except those of Li+, Na+, K+, Rb+, Ce+ and NH4+
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