Sample Questions - Chapter 3

Chemical Reactions and Reaction Stoichiometry

Examples of
Multiple Choice Questions

1.: Balance the following equation with the smallest whole number coefficients. Choose the answer that is the sum of the coefficients in the balanced equation. Do not forget coefficients of "one."
PtCl₄ + XeF₂ PtF₆ + ClF + Xe; (a) 16; (b) 22; (c) 24; (d) 26; (e) 32
2.: Balance the following equation with the smallest whole number coefficients. Choose the answer that is the sum of the coefficients in the balanced equation. Do not forget coefficients of "one."
Cr₂(SO₄)₃ + RbOH Cr(OH)₃ + Rb₂SO₄; (a) 10; (b) 12; (c) 13; (d) 14; (e) 15
3.: Balance the following equation using minimum integral coefficients:
NH₃ + O₂ NO₂ + H₂O
The stoichiometric coefficient for oxygen gas O₂ is:; (a) 1; (b) 4; (c) 3; (d) 7; (e) 5
4.: When iron pyrite (FeS₂) is heated in air, the process known as "roasting" forms sulfur dioxide and iron(III) oxide. When the equation for this process is completed and balanced, using the smallest whole number coefficients, what is the coefficient for "O₂"?
___ FeS₂ + ___ O₂ ___ SO₂ + ___ Fe₂O₃; (a) 2; (b) 4; (c) 7; (d) 8; (e) 11
5.: How many moles of KBrO₃ are required to prepare 0.0700 moles of Br₂ according to the reaction:
KBrO₃ + 5KBr + 6HNO₃ 6KNO₃ + 3Br₂ + 3H₂O; (a) 0.210; (b) 0.0732; (c) 0.0704; (d) 0.220; (e) 0.0233
6.: Which of the following statements is FALSE for the chemical equation given below in which nitrogen gas reacts with hydrogen gas to form ammonia gas assuming the reaction goes to completion?
N₂ + 3H₂ 2NH₃; (a) The reaction of one mole of H₂ will produce 2/3 moles of NH₃.; (b) One mole of N₂ will produce two moles of NH₃.; (c) One molecule of nitrogen requires three molecules of hydrogen for complete reaction.; (d) The reaction of 14 g of nitrogen produces 17 g of ammonia.; (e) The reaction of three moles of hydrogen gas will produce 17 g of ammonia.
7.: Calcium carbide, CaC₂, is an important preliminary chemical for industries producing synthetic fabrics and plastics. CaC₂ may be produced by heating calcium oxide with coke:
CaO + 3C CaC₂ + CO
What is the amount of CaC₂ which can be produced from the reaction of excess calcium oxide and 10.2 g of carbon? (Assume 100% efficiency of reaction for purposes of this problem.); (a) 18.1 g; (b) 28.4 g; (c) 20.8 g; (d) 19.8 g; (e) 27.2 g
8.: Calculate the mass of hydrogen formed when 25 grams of aluminum reacts with excess hydrochloric acid.
2Al + 6HCl Al₂Cl₆ + 3H₂; (a) 0.41 g; (b) 1.2 g; (c) 1.8 g; (d) 2.8 g; (e) 0.92 g
9.: When 12 g of methanol (CH₃OH) was treated with excess oxidizing agent (MnO₄^-), 14 g of formic acid (HCOOH) was obtained. Using the following chemical equation, calculate the percent yield. (The reaction is much more complex than this; please ignore the fact that the charges do not balance.)
3CH₃OH + 4MnO₄^- 3HCOOH + 4MnO₂; (a) 100%; (b) 92%; (c) 82%; (d) 70%; (e) 55%
10.: A commercially valuable paint and adhesive stripper, dimethyl sulfoxide (DMSO), (CH₃)₂SO, can be prepared by the reaction of oxygen with dimethyl sulfide, (CH₃)₂S, using a ratio of one mole oxygen to two moles of the sulfide:
O₂ + 2(CH₃)₂S 2(CH₃)₂SO
If this process is 83% efficient, how many grams of DMSO could be produced from 65 g of dimethyl sulfide and excess O₂?; (a) 68 g; (b) 75 g; (c) 83 g; (d) 51 g; (e) 47 g
11.: The formation of ethyl alcohol (C₂H₅OH) by the fermentation of glucose (C₆H₁₂O₆) may be represented by:
C₆H₁₂O₆ 2C₂H₅OH + 2CO₂
If a particular glucose fermentation process is 87.0% efficient, how many grams of glucose would be required for the production of 51.0 g of ethyl alcohol (C₂H₅OH)?; (a) 68.3 g; (b) 75.1 g; (c) 115 g; (d) 229 g; (e) 167 g
12.: The limiting reagent in a chemical reaction is one that:; (a) has the largest molar mass (formula weight).; (b) has the smallest molar mass (formula weight).; (c) has the smallest coefficient.; (d) is consumed completely.; (e) is in excess.
13.: If 5.0 g of each reactant were used for the the following process, the limiting reactant would be:
2KMnO₄ +5Hg₂Cl₂ + 16HCl 10HgCl₂ + 2MnCl₂ + 2KCl + 8H₂O; (a) KMnO₄; (b) HCl; (c) H₂O; (d) Hg₂Cl₂; (e) HgCl₂
14.: What mass of ZnCl₂ can be prepared from the reaction of 3.27 grams of zinc with 3.30 grams of HCl?
Zn +2HCl ZnCl₂ + H₂; (a) 6.89 g; (b) 6.82 g; (c) 6.46 g; (d) 6.17 g; (e) 6.02 g
15.: How many grams of NH₃ can be prepared from 77.3 grams of N₂ and 14.2 grams of H₂? (Hint: Write and balance the equation first.); (a) 93.9 g; (b) 79.7 g; (c) 47.0 g; (d) 120.0 g; (e) 13.3 g
16.: Silicon carbide, an abrasive, is made by the reaction of silicon dioxide with graphite. SiO₂ +3C SiC + 2CO
If 100 g of SiO₂ and 100 g of C are reacted as far as possible, which one of the following statements will be correct?; (a) 111 g of SiO₂ will be left over.; (b) 44 g of SiO₂ will be left over.; (c) 82 g of C will be left over.; (d) 40 g of C will be left over.; (e) Both reactants will be consumed completely, with none of either left over.
17.: Calculate the mass of 6.00% NiSO₄ solution that contains 40.0 g of NiSO₄?; (a) 667 g; (b) 540 g; (c) 743 g; (d) 329 g; (e) none of these
18.: How many grams of water are contained in 75.0 grams of a 6.10% aqueous solution of K₃PO₄?; (a) 75.0 g; (b) 73.2 g; (c) 70.4 g; (d) 68.1 g; (e) 62.8 g
19.: The mass (in grams) of FeSO₄7H₂O required for preparation of 125 mL of 0.90 M solution is:; (a) 16 g; (b) 25 g; (c) 13 g; (d) 31 g; (e) 43 g
20.: What is the molarity of phosphoric acid in a solution labeled 20.0% phosphoric acid (H₃PO₄) by weight with a density = 1.12 g/mL?; (a) 0.98 M; (b) 2.3 M; (c) 2.7 M; (d) 3.0 M; (e) 3.6 M
21.: How many mL of 17 M NH₃ must be diluted to 500.0 mL to make a 0.75 M solution?; (a) 13 mL; (b) 22 mL; (c) 39 mL; (d) 73 mL; (e) none of these
22.: How many grams of Ag₂CO₃ are required to react with 28.5 mL of 1.00 M NaOH solution?
Ag₂CO₃ +2NaOH Ag₂O + Na₂CO₃ + H₂O; (a) 7.87 g; (b) 3.93 g; (c) 15.7 g; (d) 10.8 g; (e) 8.16 g
23.: How many milliliters of 0.200 M NH₄OH are needed to react with 12.0 mL of 0.550 M FeCl₃?
FeCl₃ + 3NH₄OH Fe(OH)₃ + 3NH₄Cl; (a) 99.0 mL; (b) 33.0 mL; (c) 8.25 mL; (d) 68.8 mL; (e) 132 mL
24.: When 250. mL of a 0.15 M solution of ammonium sulfide (NH₄)₂S is poured into 120. mL of a 0.053 M solution of cadmium sulfate CdSO₄, how many grams of a yellow precipitate of cadmium sulfide CdS are formed? The other product is (NH₄)₂SO₄. (Hint: Write out and balance the equation. Is this a limiting reagent problem? ); (a) 5.4 g; (b) 0.92 g; (c) 2.6 g; (d) 1.9 g; (e) 530 g

Answers:

1. (a) 2. (b) 3. (d) 4. (e) 5. (e) 6. (e) 7. (a) 8. (d) 9. (c) 10. (a) 11. (c) 12. (d) 13. (d) 14. (d) 15. (b) 16. (d) 17. (a) 18. (c) 19. (d) 20. (b) 21. (b) 22. (b) 23. (a) 24. (b)

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