Chemistry 6.0
Stoichiometry
Name_______________________________
Stoichiometry Problems
1) Solve the following problems using the equation, 8 Al2S3 + 24 F2 → 16 AlF3 + 3 S8
a. How many moles of fluorine are required to react with 3.55 moles of aluminum sulfide?
b. How many moles of sulfur will be produced if 4.09 moles of fluorine react?
c. How many grams of aluminum fluoride will be produced if 2.35 moles of sulfur are also
produced?
d. How many formula units of aluminum fluoride will be produced if 2.0 x 1023 molecules of
fluorine are reacted?
e. How many liters of fluorine at STP are required to react with 13.22 g of aluminum sulfide?
f. How many grams of sulfur will be produced when 0.984 g of fluorine react?
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2) How many grams of oxygen are produced if 155 grams of iron(III) oxide are decomposed by
electrolysis?
3) How many moles of water are produced if 50.0 moles of methane (CH4) are combusted?
4) How many molecules of chlorine gas are produced if 125 grams of sodium chloride are exposed to an
electric current?
5) Calculate the volume of oxygen consumed at STP during the combustion of 12.4 g of ethane (C2H6)?
6) During the synthesis of water from hydrogen and oxygen gases, 1.45 L of oxygen at 15°C and
89.3 kPa are completely reacted. How many grams of water are produced?
7) Calcium carbonate can be precipitated from a calcium hydroxide solution by bubbling carbon dioxide
through the solution. (This is the classic lab test for CO2 by using limewater). What volume of
carbon dioxide at STP is required to precipitate 3.55 g of calcium carbonate?
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8) 15.0 g of ammonium carbonate is decomposed into ammonia, carbon dioxide and water. If these three
gases were collected in a 1.5 L flask at 125 °C, calculate the total pressure in the flask after the
reaction.
9) If 2.57 L of hydrogen gas are consumed in the synthesis of ammonia, NH3(g), at STP how many liters
of nitrogen are reacted? How many liters of ammonia are produced?
10) How many moles of carbon dioxide are produced when 75 grams of aluminum carbonate are
decomposed by heating?
11) How many liters of gas are liberated at 137.6 kPa and 572°C when 399 grams of barium chlorate are
heated?
12) How many grams of precipitate are produced if 86 grams of barium phosphate are reacted with excess
sodium sulfate.
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13) What volume of oxygen is required to produce 89.4 mL of carbon dioxide during the combustion of
methylpropane (C4H10) at STP?
14) How many moles of aluminum are required to react with 27.8 moles of iron(III) oxide?
15) If 25.9 grams of Pb(NO3)2 are reacted with NaI, how many moles of precipitate are produced?
Percent Yield
16) When 13.82 g of silver nitrate are reacted with sodium phosphate, 8.71 g of silver phosphate are
recovered. Calculate the percent yield of silver phosphate in this reaction.
17) When 15.8 grams of NH3 is reacted with oxygen, 21.8 grams of NO is produced. If water is also
produced in the reaction, calculate the percent yield of NO.
18) Coal gasification is a process that converts coal into methane gas. If this reaction has a percent yield
of 85.0%, how much methane can be obtained from 1250 grams of carbon?
2 C + 2 H2O → CH4 + CO2
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19) Given the following set of reactions for the production of NaBr, what is the percent yield when 1.020
kg of Fe yields 5.000 kg of NaBr? (Balance the equations!)
Fe + Br2 → FeBr2
FeBr2 + Br2 → Fe3Br8
Fe3Br8 + Na2CO3 → NaBr + CO2 + Fe3O4
20) The Ostwald Process for producing nitric acid from ammonia consists of the following given
reactions. If the yield in each step is 94%, how many grams of nitric acid can be produced from 5.00
kg of ammonia?
4 NH3 + 5 O2 → 4 NO + 6 H2O
2 NO + O2 → 2 NO2
3 NO2 + H2O → 2 HNO3(aq) + NO
Limiting Reagents (Limiting Reactants)
2 AgNO3 + CaCl2 → 2 AgCl + Ca(NO3)2
21) A student combines 1.05 moles of silver nitrate and 3.19 moles of calcium chloride according to the
equation above:
a. Determine the limiting reagent.
b. How many grams of silver chloride will precipitate?
c. How many grams of the excess reactant will be present after the reaction?
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22) A student combines 16.5 g of magnesium oxide with 10.3 g of tetraphosphorus decoxide according to
the equation:
6 MgO + P4O10 → 2 Mg3(PO4)2
a. Determine the limiting reagent.
b. If 12.2 g of magnesium phosphate are recovered, what is the percent yield of the reaction?
c. How many grams of the excess reactant will be present after the reaction?
23) A student adds 1.46 g of solid potassium chloride to a solution containing 0.250 moles of lead(II)
nitrate. Determine the mass of each reactant and each product present after the reaction is complete.
Solution Stoichiometry
24) If 25.0 g of a 15.6 % sodium sulfate solution is completely reacted with barium nitrate, how many
grams of precipitate will form?
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25) Solve the following problems using the equation: 2 Fe(s) + 3 H2SO4(aq)→ Fe2(SO4)3(aq) + 3 H2(g)
a. If excess iron is added to 25.0 mL of a 0.100 M sulfuric acid solution, how many molecules of
hydrogen gas will be produced?
b.
If 0.31 g of iron react completely, determine the molarity of the resulting iron(III) sulfate
solution. Assume the addition of iron does not significantly alter the solution volume.
c. What volume of hydrogen gas at 25°C and 624 torr will be produced when 25.6 g of iron is
added to 20.0 mL of a 0.150 M sulfuric acid solution?
26) Enough Pb(NO3)2 is added to 450 g of water to prepare a 1.50 m solution. If NaI is added in excess,
how many moles of lead(II) iodide are produced?
27) If 51.0 mL of 0.250 M calcium nitrate is combined with 62.3 mL of 0.370 M sodium phosphate,
calculate the mass of the precipitate.
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28) Hydrogen gas is produced in a eudiometer tube from the reaction between magnesium and 6.0 M
hydrochloric acid by the method of water displacement. Once the reaction is complete, the
eudiometer is adjusted so that the water level inside the tube is equal to the water level outside of the
tube. The hydrogen’s volume is determined to be 34.5 mL. The barometric pressure is 751 torr and
the temperature of the hydrogen (determined by measuring the water temperature) is 45°C.
a. How many grams of magnesium ribbon reacted?
b. How many milliliters of the acid solution reacted?
29) If 24.55 g of solid aluminum hydroxide is required to completely neutralize 27.1 mL of a sulfuric acid
solution, what is the molarity of the acid?
Titrations
30) 139.8 mL of 1.50 M KOH is required to neutralize 50.0 mL of HNO3. What is the molarity of the
HNO3?
31) Determine the molarity of hydrochloric acid given the following data:
Initial buret reading (mL)
Final buret reading (mL)
HCl
1.5
37.6
1.75 M NaOH
0
22.3
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32) 24.9 mL of 2.88 M Ca(OH)2 completely neutralizes 38.9 mL of an HBr solution. What is the molarity
of the HBr?
33) Determine the molarity of strontium hydroxide given the following data:
Initial buret reading (mL)
Final buret reading (mL)
Sr(OH)2
11.0
49.2
0.202 M HClO4
5.0
38.6
Stoichiometry and Enthalpy Changes
34) C2H5OH + 3O2  2CO2 + 3H2O
∆Ho = −1366.7 kJ
a. If this reaction gives off 951 kJ of heat, how many molecules of water will be produced?
b. Will this reaction cause the surroundings to increase or decrease in temperature?
35)
H2 + Br2 + 72.80 kJ  2HBr
a. How much heat will be absorbed when 38.2 g of bromine reacts with 7.23 L of hydrogen at
STP?
b. Is this reaction endothermic or exothermic?
36) N2 + O2 + 180 kJ  2NO
a. How much heat is required to react 13.7 mL of N2 at 25°C and 101.325 kPa?
b. Draw an energy diagram for this reaction
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37) S8 + 12 O2  8 SO3
∆Ho = -3165.6 kJ
a. How much heat will be released when 6.44 g of sulfur reacts?
b. If this quantity of heat is transferred to 259 grams of iron at 22.0°C, what will be the final
temperature of the iron?
c. Is this reaction endothermic or exothermic?
38) C + O2  CO2
∆Ho = −393.5 kJ
a. How many grams of carbon would be required to liberate 284 kJ of thermal energy?
b. Draw an energy diagram for this reaction.
c. How many grams of ice at 0°C can be melted from the heat released from the production
of 8.99 L CO2 at STP?
39) P4 + 10 Cl2  4 PCl5
∆Ho = −1772 kJ
a. Determine the amount of heat produced if 1.98 mol of chlorine gas are reacted.
b. What mass of molten aluminum can be vaporized at its boiling point if the heat produced
above is completely transferred to the aluminum?
c. Write the thermochemical equation for this reaction.
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40) Determine ΔH for the indicated reaction and calculate the amount of thermal energy transferred when
29.8 mL of chlorine gas at 25°C and 14.7 psi?
Determining ∆H Using Heats of Formation: Balance the following equations and determine the
enthalpy change of each using the heats of formation table.
1.
C2H6 + O2 → CO2 + H2O(l)
2.
Mg(OH)2 + NH4Cl → MgCl2 + NH3 (g) + H2O(l)
3.
Fe2O3 + CO → Fe + CO2
4. NH3 (g) + O2 → NO2 + H2O(g)
5. The combustion of octane (C8H18) – Assume all products to be in the gaseous state.
6. The reaction of sodium metal with liquid water.
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7. The decomposition of potassium chlorate.
8. Given the reaction:
Ba(OH)2 + 2 NH4Cl → BaCl2 + 2 NH3 (g) + 2 H2O(l)
a. Calculate the change in enthalpy for the reaction using the heats of formation.
b. Is this reaction endothermic or exothermic?
__________________
c. Does this reaction absorb or release thermal energy? __________________
d. Which has a higher enthalpy, the reactants or products?
__________________
e. Draw an enthalpy diagram for this reaction.
f. How many kilojoules of thermal energy are transferred if 13.5 L NH3 are produced at STP?
Review
41) Answer the following questions regarding a gaseous hydrocarbon compound that has a percent
composition of 75.0% carbon and 25.0% hydrogen.
a. What is the empirical formula of the compound?
b. If this compound effuses 2.107 times faster than chlorine gas, determine the molar mass and
the molecular formula for the hydrocarbon.
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c. Write a balanced equation for the combustion of this hydrocarbon (all gaseous substances).
d. If 3.11 g of the hydrocarbon is mixed with 13.93 g of oxygen and is ignited, what volume of
carbon dioxide will be produced at STP if the reaction has a 70.0 % yield?
e. If 624 mL of the hydrocarbon at 27°C and 526 mmHg are reacted with excess oxygen, how
many molecules of water will be produced?
f. If the carbon dioxide produced from the combustion of 3.91 g of the hydrocarbon is forced to
dissolve in 500. mL of water, what will be the molarity of the resulting solution?
g. Determine the heat of combustion for the reaction using the standards heats of formation.
h. Calculate the heat released when the mixture of 5.19 x 1023 molecules of the hydrocarbon and
3.61 L of oxygen gas at STP is ignited.
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42) If 15.6 g of solid calcium oxide is required to neutralize 50.48 mL of a nitric acid solution, determine
the molarity of the nitric acid.
43) 5.96 grams of sodium chromate is combined with 6.88 g of iron(III) nitrate. Assuming this reaction
goes to completion, identify the excess reactant and its mass that will be left over.
44) Determine the molarity of a phosphoric acid solution if 14.9 mL of the solution is titrated with
38.1 mL of 2.50 M barium hydroxide.
45) When 30.0 mL of 3.00 M sodium hydroxide is reacted with 45.0 mL of 2.50 M iron(III) chloride,
2.69 g of precipitate is recovered. Determine the percent yield of the reaction.
46) How many formula units of the precipitate are produced by the addition of 2.59 g sodium carbonate to
25.0 mL of a 0.750 M iron(III) chloride solution?
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47) Given the mechanism below, determine the volume of chlorine gas at 3.11 atm and 65.0°C that can be
produced from 75.26 g of potassium chlorate if the overall process is 68.3% efficient.
2 KClO3 → 2 KCl + 3 O2
2 KCl + Pb(C2H3O2)2 → PbCl2 + 2 KC2H3O2
PbCl2 + F2 → PbF2 + Cl2
48) Determine the molarity of calcium hydroxide solution if 18.97 mL of the solution is titrated with
21.36 mL of 1.50 M hydrochloric acid.
49) Given the reaction:
C6H12O6 + 6 O2→ 6 CO2 + 6 H2O(g)
a. Calculate the change in enthalpy for the reaction using the heats of formation.
b. Is this reaction endothermic or exothermic?
__________________
c. Does this reaction absorb or release thermal energy? __________________
d. Which has a higher enthalpy, the reactants or products?
__________________
e. Draw an enthalpy diagram for this reaction.
f. If this reaction produces 3.74 x 1022 molecules of carbon dioxide, how many kilojoules of
thermal energy were transferred?
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50) Determine the volume of nitrogen monoxide at STP if the reaction below releases 844 kJ of heat.
4NH3 + 5O2  4NO + 6H2O ∆Ho = −1170 kJ
51) How many grams of iron(III) carbonate can be precipitated by the addition of solid sodium carbonate
to 25.0 g of a 12.5% iron(III) chloride solution?
Cumulative Review Questions
52) Convert the following:
a. 621 mg =
_________________ kg
b. 4.56 in3
_________________ L
=
c. 62.54 in/sec =
_________________ km/hr
53) Ethylene glycol, antifreeze, has a density of 1.11 g/cm3 at 20°C. What volume would 56.8 grams of
ethylene glycol occupy?
54) Convert the following to scientific notation or to common decimal form, as necessary:
a. 6212
_______________________________
b. 0.0087
_______________________________
c. 211,100
_______________________________
d. 43 x 10−3
_______________________________
e. 3.20 x 102
_______________________________
f. 5300/0.0470
_______________________________
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55) State whether the following is a physical or chemical property.
a. An iron nail is attracted to a magnet
_________________________
b. A silver spoon is tarnished in air
_________________________
c. Ice floats on liquid water
_________________________
d. Rubber objects disintegrate in smog-filled air
_________________________
56) State whether the following indicate a physical or chemical change.
a. Hydrogen gas is produced from a reaction
_________________________
b. Gasoline readily vaporizes at 87°C
_________________________
c. Mothballs sublime at room temperature
_________________________
d. Aluminum oxidizes in air
_________________________
57) What was Rutherford’s famous experiment? Describe it.
58) Determine the mass and number of electrons that carry a charge of 175 C.
59) Identify # of p+, e−, and n0 for each of the following:
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2Cr 3+
a. 24
b. 34
16 S
c.
89
38
Sr 2+
60) A certain radioactive isotope has a half-life of 14.5 hours. A 2.64 gram sample of the isotope
undergoes decay for 4.23 days. What mass of sample remains after this time period?
61) What is the mass percent of iron in iron(III) sulfate?