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CHEM 1311: General Chemistry 1, Fall 2012 Exam #3, November 10, 2012 Class section: Instructor

Section #

Class time

Qin

001

9:00 am to 9:50 am

Gavva

002

10:00 am to 10:50 am

Dieckmann

003

11:00 am to 11:50 am

Sra

004

1:00 pm to 1:50 pm

EXAM TYPE: A _________________________________________________________________________________ Scantron Use In general: 1. For this exam, you are allowed to use a non-programmable and non-graphing calculator that you bring to your desk. You MAY NOT borrow another person’s calculator. You MAY NOT use your cell phone, PDA, or other non-calculator device as a calculator. 2. use #2 pencil ONLY to fill out Scantron sheet, not a pen or marker 3. when filling in bubble on the scantron, be sure to fill in bubble completely, and only one bubble for each entry; pay attention to line numbers on the scantron so that you put the answer in the correct spot 4. when you first get the exam, check to make sure you have all pages of the exam and one periodic table. You should also have one scantron sheet. If you don’t have any of these, contact us immediately. 5. we will announce periodically how much time has elapsed/are left 6. if you have a question, ask (if taking the exam at disability services, let your assistant know and they can call immediately to get an answer to your question) FILLING IN SCANTRON PERSONAL INFO: Bubble info: 1. I.D. NUMBER:

4-digit exam number (left justified)

2. NAME:

LAST NAME

3. TEST FORM:

exam type (A, B, C or D)

4. SUBJECT SCORE:

your section number: (see above for list)

Vertical lines: 1. NAME: GOOD LUCK!

“Exam 3”

space

FIRST NAME

space

MI (left justified)

CHEM 1311: Exam #3

November 10, 2012

Page 2 of 8

1. What is the stoichiometric coefficient for O2 when the following equation is balanced using the smallest, whole-number coefficients? ___ C3H8O(l) + ___ O2(g) → ___ CO2(g) + ___ H2O(l) A. 3 B. 5 C. 7 D. 9 E. None of the answers is correct. __________________________________________________________________________________ 2. Determine the limiting reactant (LR) and the mass (in grams) of nitrogen that can be formed from 50.0 g N2O4 (molar mass = 92.02 g mol–1) and 45.0 g N2H4 (molar mass = 32.05 g mol–1): N2O4(l) + 2 N2H4(l) → 3 N2(g) + 4 H2O(g) A. LR = N2H4; 59.0 g N2 formed B. LR = N2O4; 105 g N2 formed C. LR = N2O4; 45.7 g N2 formed D. LR = N2H4; 13.3 g N2 formed E. LR = H2O; 45.0 g N2 formed __________________________________________________________________________________ 3. The mixing of which pair of reactants will result in a precipitation reaction? A. Cu(NO3)2(aq) + Na2CO3(aq) B. K2SO4(aq) + Cu(NO3)2(aq) C. NaClO4(aq) + (NH4)2S(aq) D. NH4Br(aq) + NaI(aq) E. none of the above __________________________________________________________________________________ 4. Which of the following are strong acids? HI

HClO4

HF

HBr

A. HF, HBr B. HI, HClO4, HF, HBr C. HI, HF, HBr D. HClO4, HF, HBr E. HI, HClO4, HBr __________________________________________________________________________________ 5. Determine which of the following sets of reactants (if any) will undergo a reaction: I. II. III. IV. V.

Al(s) + Fe2+(aq) Sn(s) + K+(aq) Fe(s) + Sn2+(aq) K(s) + Al3+(aq) Al3+(aq) + Sn2+(aq)

A. I and II only B. II and V only C. I and IV only D. I, III and IV only E. none will undergo a reaction __________________________________________________________________________________ 6. According to the following reaction, what volume of 0.244 M KCl solution is required to react exactly with 50.0 mL of 0.210 M Pb(NO3)2 solution: 2 KCl(aq) + Pb(NO3)2(aq) → PbCl2(s) + 2 KNO3(aq) A. 97.4 mL B. 116 mL C. 43.0 mL D. 86.1 mL E. 58.1 mL __________________________________________________________________________________

CHEM 1311: Exam #3

November 10, 2012

Page 3 of 8

7. Consider the following reaction: C3H7SH + 6 O2 → 3 CO2 + SO2 + 4 H2O How many moles of oxygen are required to produce 2.33 moles of water? Assume that there is excess C3H7SH present: A. 1.55 mol B. 3.50 mol C. 2.33 mol D. 4.14 mol E. 6.21 mol __________________________________________________________________________________ 8. Which of the following are weak electrolytes? HClO3

HNO2

NH3

AgNO3

A. HClO3, AgNO3 B. HClO3, HNO2, NH3, AgNO3 C. HNO2, AgNO3 D. HNO2, NH3 E. HClO3, HNO2, AgNO3 __________________________________________________________________________________ 9. Give the net ionic equation for the reaction that occurs when aqueous solutions of Al(C2H3O2)3 and LiNO3 are mixed: A. Al3+(aq) + 3 NO3–(aq) → Al(NO3)3(s) B. Li+(aq) + C2H3O2 –(aq) → LiC2H3O2(s) C. Al3+(aq) + 3 NO3–(aq) + Li+(aq) + C2H3O2–(aq) → Al(NO3)3(aq) + LiC2H3O2(s) D. 3 Li+(aq) + (C2H3O2)33–(aq) → Li3(C2H3O2)3(s) E. no reaction occurs __________________________________________________________________________________ 10. What is the stoichiometric coefficient for Ag(s) when the following equation is balanced using the smallest, whole-number coefficients? ___ Al(s) + ___ Ag+(aq) → ___ Al3+(aq) + ___ Ag(s) A. 1 B. 2 C. 3 D. 4 E. 5 __________________________________________________________________________________ 11. Combustion analysis of 63.8 g of a compound containing C, H and O, produced 145.0 g of CO2 and 59.38 g of H2O. What is the empirical formula for the compound? A. C5H2O B. CHO C. C3H6O D. C3H7O E. C6HO3 __________________________________________________________________________________ 12. Choose the statement below that is true: A. a weak acid solution consists of mostly nonionized acid molecules. B. the term “strong electrolyte” means that the substance is extremely reactive. C. a strong acid solution consists of only partially ionized acid molecules. D. the term “weak electrolyte” means that the substance is inert. E. a molecular compound that does not ionize in solution is considered a strong electrolyte. __________________________________________________________________________________

CHEM 1311: Exam #3

November 10, 2012

Page 4 of 8

13. The spectator ion(s) in the aqueous reaction between HCl and NH3 is/are: A. H3O+ and NH3 B. H+(aq), Cl–(aq), NH3(aq) and NH4+(aq) + – D. H+(aq), Cl–(aq) and NH4+(aq) C. Cl (aq) and NH4 (aq) – E. Cl (aq) __________________________________________________________________________________ 14. When HF(g) is dissolved in water, which of the following species below is present in the largest amount in the solution? A. H3O+ B. HF(aq) C. H+(aq) D. F–(aq) E. OH–(aq) __________________________________________________________________________________ 15. How many milliliters of a 0.266 M LiNO3 solution are required to make 150.0 mL of a 0.075 M LiNO3 solution? A. 53.2 mL B. 42.3 mL C. 18.8 mL D. 23.6 mL E. 35.1 mL __________________________________________________________________________________ 16. What is the theoretical yield of H2S (molar mass = 150.17 g mol–1) if 4.0 mol Al2S3 and 4.0 mol H2O (molar mass = 18.016 g mol–1) are reacted according to the following balanced reaction: Al2S3(s) + 6 H2O(l) → 2 Al(OH)3(s) + 3 H2S(g) A. 12 mol H2S B. 4.0 mol H2S C. 18 mol H2S D. 6.0 mol H2S E. 2.0 mol H2S __________________________________________________________________________________ 17. Which one of these compounds should be insoluble in water? A. Hg2I2 B. MgSO4 C. (NH4)2CO3 D. BaS E. Sr(NO3)2 __________________________________________________________________________________ 18. Which of the species is undergoing oxidation in the following reaction? CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g) A. C

B. H

C. O

D. both C and H

E. no oxidation is occurring __________________________________________________________________________________ 19. Calcium phosphate reacts with sulfuric acid to form calcium sulfate and phosphoric acid. What is the stoichiometric coefficient for sulfuric acid when the chemical equation is balanced using the smallest, whole-number stoichiometric coefficients? A. 1 B. 2 C. 3 D. 4 E. None of these __________________________________________________________________________________ 20. Predict the products of a reaction between aqueous barium nitrate and aqueous potassium sulfate solutions: A. Ba(s), KNO3(aq) and K2SO4(aq) B. BaSO3(s) and KNO2(aq) C. BaSO3(s) and KNO3(aq) D. BaSO4(s) and KNO3(aq) E. Ba2SO4(s) and KNO3(aq) __________________________________________________________________________________

CHEM 1311: Exam #3

November 10, 2012

Page 5 of 8

21. When writing the molecular equation for the neutralization reaction between HClO4(aq) and NH3(aq), what is the chemical formula of the salt produced? A. (NH4)2ClO4 B. NaClO4 C. NH4ClO4 D. NH4NO3 E. NH4Cl __________________________________________________________________________________ 22. The titration of 25.0 mL of an unknown concentration H2SO4 solution requires 83.6 mL of 0.12 M LiOH solution for complete neutralization. What is the concentration of the H2SO4 solution? A. 0.20 M B. 0.40 M C. 0.10 M D. 0.36 M E. 0.25 M __________________________________________________________________________________ 23. Give the net ionic equation for the reaction that occurs when aqueous solutions of K2S and Fe(NO3)2 are mixed: A. K+(aq) + NO3–(aq) → KNO3(s) B. Fe2+(aq) + S2–(aq) + 2 K+(aq) + 2 NO3–(aq) → FeS(s) + 2 K+(aq) + 2 NO3 –(aq) C. Fe2+(aq) + S2–(aq) + 2 K+(aq) + 2 NO3–(aq) → Fe2+(aq) + S2–(aq) + 2 KNO3(s) D. Fe2+(aq) + S2–(aq) → FeS(s) E. no reaction occurs __________________________________________________________________________________ 24. What is the concentration of nitrate ions in a 0.125 M Mg(NO3)2 solution? A. 0.125 M B. 0.0625 M C. 0.375 M D. 0.250 M E. 0.160 M __________________________________________________________________________________ 25. The thermite reaction generates enough heat that the iron that is also produced is molten! Fe2O3(s) + 2 Al(s) → Al2O3(s) + 2 Fe(l) Determine the percent yield of Fe if 28.65 g are produced when 50.00 g of Fe2O3 reacts with excess Al: A. 61.03% B. 28.65% C. 57.30% D. 20.02% E. 81.93% __________________________________________________________________________________ 26. Determine the oxidation number of P in PO3 3– : A. +6 B. +3 C. 0 D. –3 E. –5 __________________________________________________________________________________ 27. What mass of calcium phosphate (molar mass = 310.18 g mol–1) is needed to prepare 650. mL of a solution having a calcium ion concentration of 0.125 M? A. 16.8 g B. 25.2 g C. 8.40 x 103 g D. 11.0 g E. 8.40 g __________________________________________________________________________________ 28. Which one of the following is a nonelectrolyte? A. aqueous ammonium chloride solution B. aqueous glucose solution C. aqueous nickel sulfate solution D. aqueous sodium oxalate solution E. aqueous zinc nitrate solution __________________________________________________________________________________

CHEM 1311: Exam #3

November 10, 2012

Page 6 of 8

29. Which of the species is the reducing agent in the following reaction? 2 Li(s) + Fe(C2H3O2)2(aq) → 2 LiC2H3O2(aq) + Fe(s) A. Fe(s) B. Fe(C2H3O2)2 C. Li(s) D. LiC2H3O2(aq) E. C2H3O2– __________________________________________________________________________________ 30. How many grams of Li3N (molar mass = 34.833 g mol–1) can be formed from 12.15 g of Li? 6 Li(s) + N2(g) → 2 Li3N(s) A. 18.3 g B. 20.3 g C. 58.3 g D. 61.0 g E. 15.3 g __________________________________________________________________________________ 31. In which compound is the oxidation number of oxygen NOT –2? A. MgO B. Li2O C. Na2O2 D. Al2O2 E. ClO– __________________________________________________________________________________ 32. Give the net ionic equation for the reaction that occurs when aqueous solutions of sulfuric acid and potassium hydroxide are mixed: A. H+(aq) + OH–(aq) → H2O(l) B. 2 K+(aq) + SO42–(aq) → K2SO4(s) C. H+(aq) + OH–(aq) + 2 K+(aq) + SO42–(aq) → H2O(l) + K2SO4(s) D. H22+(aq) + OH–(aq) → H2(OH)2(l) E. no reaction occurs. __________________________________________________________________________________

CHEM 1311: Exam #3

November 10, 2012

Page 7 of 8

CHEM 1311: Exam #3

November 10, 2012

Page 8 of 8

Potentially Useful Information Avogadro’s Number:

NA = 6.022 x 1023

Rydberg Equation constant (for Hydrogen):

RH = 109,678 cm–1

Constant for Bohr model of H atom:

b = 2.18 x 10–18 J

Speed of light:

c = 2.998 x 108 m s–1

Planck’s constant:

h = 6.63 x 10–34 J s

1 J = 1 kg m2 s–2 electron: proton: neutron:

mass (me) = 9.1093897 x 10–28 g mass = 1.673 x 10–24 g mass = 1.675 x 10–24 g

charge (e) = –1.60 x 10–19 C...