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Chemistry Saturday Study Session 1, Class 1--Stoichiometry
1. A 27.0g sample of an unknown hydrocarbon was burned in excess oxygen to form 88.0g
of carbon dioxide and 27.0g of water. What is a possible molecular formula for the
hydrocarbon?
A. CH4
B. C2H2
C. C4H3
D. C4H6
2. When a hydrate of Na2CO3 (106g/mol) is heated until all the water is removed, it loses
54.3% of its mass. The formula of the hydrate is…
A. Na2CO3 · 7 H2O
B. Na2CO3 · 5 H2O
C. Na2CO3 · 3 H2O
D. Na2CO3 · H2O
BrO3- + 5Br- + 6H+ → 3Br2 + 3H2O
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Chemistry Saturday Study Session 1, Class 1--Stoichiometry
3. If 25.0mL 0.200M BrO3- is mixed with 30.0mL of 0.500M Br- solution that contains a
large excess of H+, the amount of Br2 formed, according to the equation above, is…
A. 9.00 x 10-3 mol
B. 1.35 x 10-3 mol
C. 1.50 x 10-2 mol
D. 1.62 x 10-2 mol
CS2(l) + 3O2(g) → CO2(g) + 2SO2(g)
4. What volume of O2(g) is required to react with excess CS2(s) to produce 4.0L of CO2(g)
at 0°C and 1atm?
A. 1/3 x 22.4L
B. 12L
C. 22.4L
D. 3 x 22.4L
5. A compound contains 1.10mol of K, 0.55mol of Te, and 1.65mol of O. What is the
empirical formula of this compound?
A. KTeO
B. KTe2O
C. K2TeO6
D. K2TeO3
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Chemistry Saturday Study Session 1, Class 1--Stoichiometry
4NH3 + 5O2 → 4NO + 6H2O
6. The balanced chemical equation for the reaction of ammonia and oxygen gas is given
above. Given the initial condition shown below…
…which of these answer choices best depicts the same container after the reaction goes to
completion?
A
B
C
D
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Chemistry Saturday Study Session 1, Class 1--Stoichiometry
NaOH(aq) + MgCl2(s) →
2NaCl(aq) + Mg(OH)2(s)
7. MgCl2 and NaOH react according to the equation shown above. A 0.050mol sample of
solid MgCl2 is added to 150.mL of 0.200M NaOH solution. Which of the diagrams
below best depicts the results after the mixture reacts as completely as possible?
Mg2+
Mg2+
OH-
OH-
Na+
A
Na+
Mg2+
B
Mg2+
Cl-
Cl-
Na+
No precipitate
Mg2+
Cl-
Na+
Cl-
Solid Mg(OH)2
Na+
Cl-
Cl-
Na+
C
Na+
Na+
D
Na+
ClNa+
Cl-
Cl-
Solid Mg(OH)2
Na+
Cl-
Solid Mg(OH)2
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Chemistry Saturday Study Session 1, Class 1--Stoichiometry
8. A dilute aqueous solution contains 0.25mol NaBr and 0.25mol CaBr2. What is the
minimum number of moles of AgNO3 that must be added in order to precipitate all the
Br- as AgBr(s)?
A. 1.0mol
B. 0.75mol
C. 0.50mol
D. 0.25mol
3Ag(s) + 4HNO3 ↔ 3AgNO3 + NO(g) + 2H2O
9. The reaction of silver metal and dilute nitric acid proceeds according to the equation
above. If 10.0mol of powdered silver is added to 10.0mL of 6.0M nitric acid, the number
of moles of NO gas that can be formed is
A. 0.015mol
B. 0.020mol
C. 0.030mol
D. 0.045mol
10. The weight of H2SO4 (98.1g/mol) in 50.0mL of 6.00 molar solution is
A. 3.10g
B. 12.0g
C. 29.4g
D. 294g
Page 6 of 6
Chemistry Saturday Study Session 1, Class 1--Stoichiometry
1. Answer the following questions that relate to chemical reactions.
a) Iron(III) oxide can be reduced with carbon monoxide according to the following
equation.
Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g)
A 16.2 L sample of CO(g) at 1.50 atm and 200. °C is combined with 15.39 g of Fe2O3(s).
i) How many moles of CO(g) are available for the reaction?
ii) What is the limiting reactant for the reaction? Justify your answer with
calculations.
iii) How many moles of Fe(s) are formed in the reaction?
b) In a reaction vessel, 0.600 mol of Ba(NO3)2(s) and 0.300 mol of H3PO4(aq) are
combined with deionized water to a final volume of 2.00 L. The reaction represented
below occurs.
3 Ba(NO3)2(aq) + 2 H3PO4(aq) → Ba3(PO4)2(s) + 6 HNO3(aq)
i) Calculate the mass of Ba3(PO4)2(s) formed.
ii) Calculate the pH of the resulting solution.
iii) What is the concentration, in mol·L–1, of the nitrate ion, NO3–(aq), after the
reaction reaches completion?
2. A student placed a sample of an unknown hydrate of copper(II) sulfate into a clean, dry
crucible and heated it three times, with the results shown below…
mass of clean, dry crucible
mass of hydrated compound and crucible
mass of crucible and contents after 1st heating
mass of crucible and contents after 2nd heating
mass of crucible and contents after 3rd heating
15.96g
20.03g
19.01g
18.56g
18.55g
a) Justify the student’s conclusion that the compound was dry after the third heating.
b) If the student failed to cover the crucible and some solid CuSO4 spattered out during the
heating process, would you expect the student’s calculated mass of water in the
hydrate to be too high, too low, or correct? Explain.
c) Explain how you would use the data collected by the student to determine the formula of
the unknown hydrate (CuSO4 · _____H2O). Calculations are not required.