Unit 1

STOICHIOMETRY
Note: For questions referring to solutions, assume
that the solvent is water unless otherwise stated.
1. When a 1.25–gram sample of limestone was
dissolved in acid, 0.44 gram of CO2 was generated.
CaCO3 + 2 H+ → Ca+2 + H2O + CO2
If the rock contained no carbonate other than
CaCO3, what is the mass percent of CaCO3 in the
limestone?
(A) 35%
(B) 44%
(C) 67%
(D) 80%
(E) 100%
2. It is known that SO2 (molar mass 64 grams) can
be removed from a stream of waste gases by
bubbling the gases through KOH solution.
SO2 + 2 KOH → K2SO3 + H2O
What is the maximum mass of SO2 that could be
removed by 1.000 x 103 liters of 0.25 M KOH
solution?
(A) 4.0 kg
(B) 8.0 kg
(C)16 kg
1
1
(D) 2.0 x 10 kg (E) 4.0 x 10 kg
3. What volume of 0.150–molar HCl is required to
neutralize 25.0 mL of 0.120–molar Ba(OH)2?
(A) 20.0 mL
(B) 30.0 mL
(C) 40.0 mL
(D) 60.0 mL
(E) 80.0 mL
4. If 87 grams of K2SO4 (molar mass 174 grams) is
dissolved in enough water to make 250 mL of
solution, what are the concentrations of the
potassium and the sulfate ions?
[K+]
[SO42–]
(A)
0.020 M
0.020 M
(B)
1.0 M
2.0 M
(C)
2.0 M
1 .0 M
(D)
2.0 M
2.0 M
(E)
4.0 M
2.0 M
5. In which of the following is the mass ratio of
ruthenium to oxygen closest to 3:1?
(A) RuO3
(B) RuO2
(C) RuO
(D) Ru2O
(E) Ru2O3
6. Samples of F2 gas and Xe gas are mixed in a
container of fixed volume. The initial partial
pressure of the F2 gas is 8.0 atmospheres and that
of the Xe gas is 1.7 atmospheres. When all of the
Xe gas reacted, forming a solid compound, the
pressure of the unreacted F2 gas was 4.6
atmospheres. The temperature remained constant.
What is the formula of the compound?
(A) XeF
(B) XeF3
(C) XeF4
(D) XeF6
(E) XeF8
7. How many moles of solid Ba(NO3)2 should be
added to 300. mL of 0.20–molar Fe(NO3)3 to
increase the concentration of the NO3– ion to 1.0–
molar? (Assume that the volume of the solution
remains constant.)
(A) 0.060 mole
(B) 0.12 mole (C) 0.24 mole
(D) 0.30 mole
(E) 0.40 mole
8. When a hydrate of K2CO3 (MW = 138) is
heated until all the water is removed, it loses 51.1
percent of its mass. The formula of the hydrate is
(A) K2CO3.10 H2O
(B) K2CO3.8 H2O
(C) K2CO3.6 H2O
(D) K2CO3.4 H2O
.
(E) K2CO3 2 H2O
9. 2 K + 2 H2O  2K+ + 2 OH– + H2
When 0.400 mole of potassium reacts with excess
water at standard temperature and pressure as
shown, the volume of hydrogen gas produced is
(A) 1.12 liters (B) 2.24 liters (C) 3.36 liters
(D) 4.48 liters (E) 6.72 liters
10. How many grams of calcium nitrate,
Ca(NO3)2, contains 24 grams of oxygen atoms?
(A) 164 grams (B) 96 grams (C) 62 grams
(D) 50 grams
(E) 41 grams
11. The mass of element Q found in 1.00 mole of
each of four different compounds is 38.0 grams,
57.0 grams, 76.0 grams, and 114 grams,
respectively. A possible atomic weight of Q is
(A) 12.7
(B) 19.0
(C) 27.5
(D) 38.0
(E) 57.0
12. How many mL of 12.0-molar HCl must be
diluted to obtain 1.0 L of 3.0-molar HCl?
(A) 40 mL
(B) 25 mL
(C) 250 mL
(D) 1,000 mL
(E) 4,000 mL
13. The weight of H2SO4 (molar mass = 98.1) in
50.0 mL of a 6.00-molar solution is
(A) 3.10 g
(B) 12.0 g
(C) 29.4 g
(D) 294 g
(E) 3.00 x 102 g
14. A sample of 9.00 grams of aluminum metal is
added to an excess of hydrochloric acid and reacts:
2 Al + 6 H+  2 Al+3 + 3 H2
The volume of hydrogen gas produced at standard
temperature and pressure is
(A) 22.4 L
(B) 11.2 L
(C) 7.46 L
(D) 5.60 L
(E) 3.74 L
15. When 7.0 x 101 mL of 3.0-molar Na2CO3 is
added to 3.0 x 101 mL of 1.0-molar NaHCO3 the
resulting concentration of Na+ is
(A) 2.0 M
(B) 2.4 M
(C) 4.0 M
(D) 4.5 M
(E) 7.0 M
16. A 27.0–gram sample of an unknown
hydrocarbon was burned in excess oxygen to form
88.0 grams of carbon dioxide and 27.0 grams of
water. What is a possible molecular formula of the
hydrocarbon?
(A) CH4
(B) C2H2
(C) C4H3
(D) C4H6
(E) C4H10
17. A compound is heated to produce a gas whose
molecular weight is to be determined. The gas is
collected by displacing water in a water–filled flask
inverted in a trough of water. Which of the
following is necessary to calculate the molecular
weight of the gas, but does NOT need to be
measured during the experiment?
(A) Mass of the compound used in the
experiment
(B) Temperature of the water in the trough
(C) Vapor pressure of the water
(D) Barometric pressure
(E) Volume of water displaced from the flask
18. A student wishes to prepare 2.00 liters of
0.100–molar KIO3 (molecular weight 214). The
proper procedure is to weigh out
(A)42.8 g of KIO3 and add 2.00 kg of H2O
(B)42.8 g of KIO3 and add H2O until the final
homogeneous solution has a volume of
2.00 liters
(C)21.4 g of KIO3 and add H2O until the final
homogeneous solution has a volume of
2.00 liters
(D)42.8 g of KIO3 and add 2.00 liters of H2O
(E)21.4 g of KIO3 and add 2.00 liters of H2O
19. A 20.0–mL sample of 0.200–molar K2CO3
solution is added to 30.0 mL of 0.400–molar
Ba(NO3)2 solution. Barium carbonate precipitates.
The concentration of barium ion, Ba2+, in solution
after reaction is
(A) 0.150 M
(B) 0.160 M
(C) 0.200 M
(D) 0.240 M
(E) 0.267 M
20. What number of moles of O2 is needed to
produce 14.2 grams of P4O10 from P? (The molar
mass of P4O10 = 284)
(A) 0.0500 mole
(B) 0.0625 mole
(C) 0.125 mole
(D) 0.250 mole
(E) 0.500 mole
21. 3 Ag(s) + 4 HNO3 
3 AgNO3 + NO(g) + 2 H2O
The reaction of silver metal and dilute nitric acid
proceeds according to the equation above. If 0.10
mole of powdered silver is added to 10.0 mL of
6.0–molar nitric acid, the number of moles of NO
gas that can be formed is
(A) 0.015 mole
(B) 0.020 mole
(C) 0.030 mole
(D) 0.045 mole
(E) 0.090 mole
22. The alkenes are compounds of carbon and
hydrogen with the general formula CnH2n. If 0.561
gram of any alkene is burned in excess oxygen,
what number of moles of H2O is formed?
(A) 0.0400 mole
(B) 0.0600 mole
(C) 0.0800 mole
(D) 0.400 mole
(E) 0.800 mole
23. A sample of a pure compound was found to
contain 1.201 g of carbon, 0.202 g of hydrogen,
and 7.090 g of chlorine. What is the empirical
formula of the compound?
(A) CHCl3
(B) CH2Cl
(C) CH2Cl2
(D) CH3Cl
(E) C2H2Cl
24. When 0.600 moles of BaCl2(aq) is mixed with
0.250 moles of K3AsO4(aq) they react:
3 BaCl2 + 2 K3AsO4  Ba3(AsO4)2 + 6 KCl
What is the maximum number of moles of solid
Ba3(AsO4)2 that could be formed?
(A) 0.125
(B) 0.200
(C) 0.250
(D) 0.375
(E) 0.500
25. If 0.600 mol of X is found to react completely
with 4.80 g of O2 gas, what is the empirical
formula of the resultant oxide?
(A) X2O
(B) XO2
(C) X4O
(D) XO4
(E) XO
26. H2(g) + 1/2 O2(g)  H2O(l) ° = –300 kJ
2 Na(s) + 1/2 O2(g)  Na2O(s) ° = –400 kJ
Na(s) + 1/2 O2(g) + ½ H2(g)  NaOH(s)
° = –450 kJ
Based on the information above, what is the
standard enthalpy change for the reaction below?
Na2O(s) + H2O(l)  2 NaOH(s)
(A) –1,150 kJ
(B) –950 kJ (C) –700 kJ
(D) –200 kJ
(E) +150 kJ (F) +250 kJ
27. CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(l)
H° = –890 kJ
Hfº H2O(l) = –280 kJ/mol
fº CO2(g) = –390 kJ/mol
What is the standard heat of formation of methane,
Hfº CH4(g), as calculated from the data above?
(A) 220 kJ/mol
(B) –220 kJ/mol
(C) 60 kJ/mol
(D) –60 kJ/mol
(E) 1560 kJ/mol
(F) –1560 kJ/mol
28. Which of these is NOT a state function?
(A) Pressure
(B) Heat
(C) Energy
(D) Entropy
(E) Free Energy

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