Unit II Exam
Directions: Mark the letter of the correct answer on your answer sheet with medium lead (No. 2) pencil. You may use your exam sheet for scratch paper. You may keep your exam paper. Each question is worth 6 points for a total of 120 points possible. No additional penalty for guessing. There is only one correct answer per question Your exam will be graded on the basis of 100 points (i.e. 20 bonus points built in.) Under your name on the scantron mark either "W" for white form or "C" for color form.
1. Sulfur dioxide may be prepared by the reaction of sulfur with oxygen gas according to the chemical equation below.
__ S8(s) + __ O2(g) ® __ SO2(g)
What are the respective coefficients when the equation is balanced with the smallest whole numbers?
a) 8, 8, 8 b) 2, 16, 8 #c) 1, 8, 8 d) 2, 16, 16 e) 1, 2, 1
2. Metals react with oxygen to give oxides with the general formula MxOy. Write a balanced chemical equation for the reaction of cobalt with oxygen to yield cobalt (III) oxide.
a) Co(s) + O2(g) ® Co2O3(s)
#b) 4 Co(s) + 3 O2(g) ® 2 Co2O3(s)
c) 2 Co(s) + 3 O2(g) ® Co2O3(s)
d) 6 Co(s) + O2(g) ® 2 Co3O(s)
e) 2 Co(s) + 3 O2(g) ® 2 CoO3(s)
3. The products of the complete combustion of a hydrocarbon are carbon dioxide and water. Write a balanced chemical equation for the combustion of butane, C4H10.
#a) 2 C4H10(g) + 13 O2(g) ® 8 CO2(g) + 10 H2O(g)
b) C4H10(g) ® 4 C(s) + 4 H2(g)
c) C4H10(g) + 13 O2(g) ® 4 CO2(g) + 5 H2O(g)
d) C4H10(g) + 9 O2(g) ® 4 CO2(g) + 5 H2O(g)
e) None of the above are correctly balanced.
4. Dinitrogen trioxide, a blue solid, dissociates to form nitrogen monoxide and nitrogen dioxide gases. What mass of nitrogen dioxide is formed from the decomposition of 12.8 g of N2O3?
a) 5.05 g b) 6.40 g #c) 7.75 g d) 12.8 g e) 21.1 g
5. Iron reacts with hydrochloric acid to produce iron (II) chloride and hydrogen gas.
Fe(s) + 2 HCl(aq) ® FeCl2(aq) + H2(g)
How many moles of HCl will react with 3.5 moles of Fe?
a) 1.0 mol b) 1.8 mol c) 2.0 mol #d) 7.0 mol e) 8.5
6. The numbers preceding the formulas in chemical equations are referred to as the ________ coefficients.
7. Methane reacts with oxygen to form carbon dioxide and water.
CH4(g) + 2 O2(g) ® CO2(g) + 2 H2O(g)
All of the following statements concerning this reaction are correct EXCEPT
a) two moles of water are formed per one mole of methane consumed.
#b) two moles
oxygen are consumed per one mole of methane consumed.
c) the combined mass of reactants consumed equals the mass of products formed.
#d) two grams of oxygen are consumed per each gram of carbon dioxide formed.
e) three moles of gases are formed per each three moles of gases consumed.
Note: because of a typo, there were two possible answers for Question 7
8. What is the expected outcome for the following reaction?
2KCl(aq) + Hg2(NO3)2(aq)®
a) A precipitate of HgCl2 will form
b) No precipitate will form
c) A redox reaction will occur
#d) A precipitate of Hg2Cl2 will form
e) A precipitate of both KNO3 will form and Hg2Cl2 will form.
9. What is the change in the number of electrons for nitrogen in the following reaction?
2KNO2(s) + O2(g)® 2KNO3(s)
a) no change, this is a combination reaction not a redox reaction
b) one electron gained
#c) two electrons lost
d) two electrons gained
e) one electron lost
10. In the reaction above, all of the statements are correct EXCEPT
a) Oxygen is the oxidizing agent.
b) The oxidation state of elemental oxygen is zero.
c) KNO2 is the reducing agent
#d) KNO3 is the oxidizing agent
e) The oxidation state for potassium is +1.
11. Copper reacts with nitric acid to produce copper nitrate, nitrogen dioxide gas, and water.
Cu(s) + 4 HNO3(aq) ® Cu(NO3)2(aq) + 2 NO2(g) + 2 H2O(l)
If you have 0.60 moles of Cu,
#a) you need at least 2.4 moles of HNO3 to produce 1.2 moles of NO2.
b) you need at least 0.60 moles of HNO3 to produce 0.60 moles of Cu(NO3)2.
c) you need at least 2.4 moles of HNO3 to produce 2.4 moles of NO2.
d) you need at least 0.15 moles of HNO3 to produce 0.60 moles of Cu(NO3)2.
e) you need at least 0.30 moles of HNO3 to produce 0.60 moles of NO2.
12. Sulfur trioxide is made from the reaction of sulfur dioxide and oxygen. How many grams of SO3 can be made from the reaction of 1.91 g SO2 with 1.29 g O2?
2 SO2(g) + O2(g) ® 2 SO3(g)
#a) 2.39 g b) 3.20 g c) 3.23 g d) 4.77 g e) 6.46
13. Which of the following compounds are likely to be soluble in water: Ni(OH)2, ZnCl2, CuS, Fe2(CO3)3, AgCl, and Pb(NO3)2?
#b) ZnCl2 and Pb(NO3)2
c) CuS and AgCl
d) Fe2(CO3)3 and Ni(OH)2
e) none of the compounds are soluble
14. Which one of the following solutions will have the highest electrical conductivity?
a) 0.010 M KCl
b) 0.010 M CaI2
c) 0.010 M MgSO4
#d) 0.010 M Al(NO3)3
e) 0.010 M Na2SO4
15. How many liters of 0.1107 M NaOH contain 10.00 g of NaOH?
a) 0.7290 L b) 1.107 L #c) 2.258 L d) 3.198 L e) 4.428 L
16. If 0.1500 g of impure soda ash (Na2CO3) is titrated with 21.99 mL of 0.1043 M HCl, what is the percent purity of the soda ash?
Na2CO3(aq) + 2 HCl(aq) ® 2 NaCl(aq) + H2O(l) + CO2(g)
a) 12.15% b) 16.21% c) 48.62% d) 73.94% #e) 81.03%
17. Which of the following chemical equations represent oxidation-reduction reactions?
1) Zn(s) + CuSO4(aq) ® ZnSO4(aq) + Cu(s)
2) SrO(s) + H2O(l) ® Sr(OH)2(aq)
3) AgNO3(aq) + NaI(aq) ® AgI(s) + NaNO3(aq)
#a) 1 b) 2 c) 1 and 2 d) 1 and 3 e) 2 and 3
18. What is the oxidation number of each atom in potassium sulfate?
a) K = +1, S = 0, O = -2
b) K = -1, S = +5, O = -2
#c) K = +1, S = +6, O = -2
d) K = +1, S = +6, O = -1
e) K = -1, S = -2, O = +4
19. Which compound is the reducing agent in the reaction below?
I-(aq) + ClO-(aq) ® IO-(aq) + Cl-(aq)
#a) I- b) ClO- c) H2O d) IO- e) Cl-
20. Which of the following compounds is a weak acid?
a) HCl #b) HF c) HBr d) HNO3 e) HClO4