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REVIEW Unit 5 - Stoichiometry
Balancing Equations 1. Balance the following equations:
a) ___Cr (s) + ___O2 (g) ___Cr2O3 (s) 4 + 3 2
b) ___Cu2S (s) + ___O2 (g) ___Cu (s) + ___SO2 (g) 1 + 1 2 + 1
c) ___C6H5CH3 (ℓ) + ___O2 (g) ___H2O (ℓ) + ___CO2 (g) 1 + 9 4 + 7
2. Balance the following equations and name the reaction products:
a) ___Fe2O3 (s) + ___Mg (s) ___MgO (s) + ___Fe (s) 1 + 3 3 + 2 (Magnesium Oxide; Iron)
b) ___AlCl3 + (s) + ___H2O (ℓ) ___Al(OH)3 (s) + ___HCl (aq) 1 + 3 1 + 3 (Aluminum Hydroxide; Hydrochloric Acid)
c) ___NaNO3 (s) + ___H2SO4 (aq) ___Na2SO4 (s) + ___HNO3 (g)
2 + 1 1 + 2 (Sodium Sulfate; Nitric Acid)
d) ___NiCO3 (s) + ___HNO3 (aq) ___Ni(NO3)2 (aq) +___CO2 (g) + ___H2O (ℓ) 1 + 2 1 + 1 + 1 (nickel II nitrate; carbon dioxide; water)
3. Balance the following equations: a) The synthesis of urea , a common fertilizer
___CO2 (g) + ___NH3 (g) ___NH2CONH2 (s) + ___H2O (ℓ)
1 + 2 1 + 1
b) Reactions used to make uranium (VI) fluoride for the enrichment of natural uranium
___UO2 (s) + ___HF (aq) ___UF4 (s) + ___H2O (ℓ) 1 + 4 1 + 2
___UF4 (s) + ___F2 (g) ___UF6 (s) 1 + 1 1 c) The reaction to make titanium (IV) chloride, which is then converted to titanium metal
___TiO2 (s) + ___Cl2 (g) + ___C (s) ___TiCl4 (ℓ) + ___CO (g) 1 + 2 + 2 1 + 2
___TiCl4 (ℓ) + ___Mg (s) ___Ti (s) + ___MgCl2 (s)
1 + 2 1 + 2
Types of Rxns
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Directions: Write out the chemical equation for each reaction AND identify the type reaction. Remember to write (s), (ℓ), (g), or (aq) next to each substance.
4. Zinc metal + lead (II) nitrate yield zinc (II)nitrate + lead metal
5. Aluminum bromide solution + chlorine gas yield aluminum chloride solution + bromine gas
6. Sodium phosphate + calcium chloride yield calcium phosphate + sodium chloride
7. Aluminum metal + hydrochloric acid yield aluminum chloride + hydrogen gas
8. Hydrogen gas + nitrogen monoxide yield water + nitrogen gas
9. Copper metal heated with oxygen gives solid copper (II) oxide.
10. Mercury (II) nitrate solution reacts with potassium iodide solution to give mercury (II) iodide precipitate and potassium nitrate solution.
11. Aluminum metal and sulfuric acid yield aqueous aluminum sulfate and hydrogen gas.
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12. Acetic acid and lithium hydroxide solution produce water and aqueous lithium acetate.
13. Sulfur dioxide gas reacts with oxygen on a platinum catalyst surface to produce sulfur trioxide gas.
14. Sodium metal reacts with water to give sodium hydroxide solution and hydrogen gas.
15. Heating solid potassium chlorate in the presence of a manganese dioxide catalyst produces potassium chloride and oxygen gas.
General Stoichiometry 16. Aluminum reacts with oxygen to give aluminum oxide.
4 Al (s) + 3O2 (g) 2 Al2O3 (s)
If you have 6.0 mol of Al, how many moles of O2 are needed for complete reaction?
What mass of Al2O3, in grams, can be produced?
4.5 mol O2; 310 g Al2O3
17. Suppose 16.04 g of methane, CH4, is burned in oxygen. a) What are the products of the reaction?
CO2 and H2O
b) What is the balanced equation for the reaction?
1 CH4 (g) + 2 O2 (g) 1 CO2 (g) + 2 H2O (l)
c) What mass of O2, in grams, is required for complete combustion of the methane?
63.99 g O2
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d) What is the total mass of products expected from 16.04 g of methane?
80.03 g products
18. Like many metals, aluminum reacts with a halogen to give a metal halide
2 Al (s) + 3 Br2 (ℓ) Al2Br6 (s)
What quantity of Br2, in grams, is requried for complete reaction with 2.56 g of Al?
What mass of solid Al2Br6 is expected?
22.7 g Br2; 25.3 g Al2Br6
19. Iron reacts with oxygen to give iron (III) oxide, Fe2O3. a) Write a balanced equation for the reaction.
4 Fe (s) + 3 O2 (g) 2 Fe2O3 (s)
b) If an ordinary iron nail (assumed to be pure iron) has a mass of 2.68 g, what mass
(in grams) of Fe2O3 does it produce if the nail is converted completely to this oxide?
3.83 g Fe2O3
c) What mass of O2 (in grams) is required for the reaction?
1.15 g O2
20. The metabolic disorder diabetes causes a buildup of acetone (CH3COCH3) in the blood of untreated victims. Acetone, a volatile compound, is exhaled, giving the breath of untreated diabetics a distinctive odor. The acetone is produced by a breakdown of fats in a series of reactions. The equation for the last step is
CH3COCH2CO2H CH3COCH3 + CO2 What quantity of acetone can be produced from 125 mg of acetoacetic acid
(CH3COCH2CO2H)?
71.2 mg acetone
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Limiting Reactant and Percent Yield
21. Aluminum chloride, AlCl3, is an inexpensive reagent used in many industrial processes. It is made by treating scrap aluminum with chlorine according to the following balanced equation:
2 Al (s) + 3 Cl2 (g) 2 AlCl3 (s)
a) Which reactant is limiting if 2.70 g of Al and 4.05 g of Cl2 are mixed?
Cl2 is the LR
b) What mass of AlCl3 can be produced from 2.70 g of Al and 4.05 g of Cl2?
5.08 g AlCl3
c) What mass of the excess reactant remains when the reaction is completed?
1.67 g Al
22. Methanol, CH3OH, is a clean-burning, easily handled fuel. It can be made by the direct
reaction of CO and H2 (obtained from heating coal with steam):
CO (g) + 2 H2 (g) CH3OH (ℓ)
a) Starting with a mixture of 12.0 g of H2 and 74.5 g of CO, which is the limiting reactant?
CO is the LR
b) What mass of the excess reactant (in grams) remains after reaction is complete?
1.3 g H2
c) What is the theoretical yield of the methanol?
85.2 g CH3OH
23. Ammonia gas can be prepared by the reaction of a metal oxide such as calcium oxide with ammonium chloride.
CaO (s) + 2 NH4Cl (s) 2 NH3 (g) + H2O (g) + CaCl2 (s)
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a) If 112 g of CaO and 224 g of NH4Cl are mixed, what is the maximum possible
yield of NH3?
68.0 g NH3
b) What mass of the excess reactant remains after the maximum amount of ammonia has been formed?
10.0 g NH4Cl remains
24. Ammonia gas can be prepared by the following reaction:
CaO (s) + 2 NH4Cl (s) 2 NH3 (g) + H2O (g) + CaCl2 (s) If 103 g of ammonia is obtained, but the theoretical yield is 136 g, what is the percent yield of this gas?
75.7 % yield
25. The reaction of zinc and chlorine has been used as the basis of a car battery.
Zn (s) + Cl2 (g) ZnCl2 (s)
a) What is the theoretical yield of ZnCl2 if 35.5 g of zinc is allowed to react with excess chlorine?
74.0 g ZnCl2
b) If only 65.2 g of zinc chloride is obtained, what is the percent yield of the compound?
88.1% yield
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