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Please sit in Row_ Seat_ Name_PRACTICE ABCDEG Chem 105X Fall 2010 Keller Hour Exam 2 Chap 4,5 Kotz Please: Keep this booklet closed until instructed to open it.

1 Please sit in Row_ Seat_ Name_PRACTICE ABCDEG Chem 105X Fall 2010 Keller Hour Exam 2 Chap 4,5 Kotz Please: Keep this booklet closed until instructed to open it. Turn off and remove from your person all electronic items including PDAs, cell phones, earbuds, pagers, computers, programmable and graphing calculators, and other similar devices. Place them in your purse or pack on the floor or at the back of the room. Place all papers, periodic tables, books, coats, packs, on the floor or at the front or back of the room. All you need are #2 pencils & a non-programmable calculator. Exam Directions NOW PRINT YOUR NAME and fill in your STUDENT ID (a number like but not this number) and the letter of the exam on the bubble sheet. This is a closed book, 60-minute exam. Use nothing but the materials supplied to answer the questions. There are a total of 9 pages in this exam, including the cover and back sheets. The attached back sheet contains reference information including constants and periodic table. For questions 21 and 22, show your work, use the correct number of significant figures, and include proper units in answer and in the work. Write legibly: if your answer cannot be read by the grader, no credit can be given. After you begin, PRINT YOUR NAME at the top of BOTH PAGE 6 and PAGE 7.

2 Part I. Multiple Choice 4 POINTS EACH Identify the letter of the choice that best completes the statement or answers the question. PUT YOUR ANSWER ON THE BUBBLE SHEET PROVIDED. Marks in this section of the exam booklet will not be graded. 1. What is the oxidation number of iodine in potassium periodate, KIO 4? a. 1 b. 0 c. +3 d. +5 e Which of the following chemical equations show oxidation-reduction reactions? 1. Mg(s) + I 2 (aq) MgI 2 (s) 2. Pb(ClO 4 ) 2 (aq) + 2 KI(aq) PbI 2 (s) + 2 NaClO 4 (aq) 3. Fe 2 O 3 (s) + 3 CO(g) 2 Fe(s) + 3 CO 2 (g) a. 1 only b. 2 only c. 1 and 2 d. 1 and 3 e. 2 and 3 3. Magnesium burns a nitrogen gas atmosphere to produce magnesium nitride. How many moles of Mg will react with 2.6 moles of N 2? a. 1.3 mol b. 2.6 mol c. 3.9 mol d. 5.2 mol e. 7.8 mol 4. If the complete combustion of an unknown mass of ethylene produces 16 g CO 2, what mass of ethylene is combusted? C 2 H 4 (g) + 3 O 2 (g) 2 CO 2 (g) + 2 H 2 O(g) a g b g c. 5.1 g d. 8.0 g e. 13 g 1

3 5. The diagram below represents a mixture of oxygen (light) and nitrogen (dark) molecules. If the molecules in the diagram react to form N 2 O 4 according to the equation N 2 + 2O 2 N 2 O 4, then, respectively, the limiting reagent and the number of N 2 O 4 molecules formed are: a. N 2 and 1 b. N 2 and 3 c. O 2 and 2 d. O 2 and 3 e. (none) and 2 6. How many moles of Cu 2 O(s) can be produced when 0.66 mol Cu(s) is combined with 0.40 mol O 2 (g)? (Write the balanced chemical equation first.) a mol b mol c mol d mol e mol 7. Under certain conditions the reaction of ammonia with excess oxygen will produce a 24% yield of NO. What mass of NH 3 must react with excess oxygen to yield 12 g NO? 4 NH 3 (g) + 5 O 2 (g) 4 NO(g) + 6 H 2 O(g) a. 1.8 g b. 7.0 g c. 28 g d. 50. g e. 88 g 8. In 1.5 M aqueous sulfuric acid, the concentration of hydronium ions H 3 O + is... a moles/l b. 1.0 moles/l c. 1.5 moles/l d. 2.0 moles/l e. 3.0 moles/l 2

4 9. What is the mass of sodium iodide in 50.0 ml of M NaI(aq)? The atomic weight of Na is 22.99, and of I is a g b g c g d g e g 10. What volume of M Na 2 SO 4 (aq) will completely react with 50.0 ml of M Ba(NO 3 ) 2 (aq)? Na 2 SO 4 (aq) + Ba(NO 3 ) 2 (aq) BaSO 4 (s) + 2 NaNO 3 (aq) a ml b ml c ml d. 148 ml e ml 11. A battery-operated power tool, such as a cordless drill, converts a. electrostatic energy to chemical potential energy. b. mechanical energy to electrostatic energy. c. thermal energy to mechanical energy. d. thermal energy to gravitational energy. e. chemical potential energy to mechanical energy. 12. Specific heat capacity is a. the quantity of heat needed to change the temperature of 1.00 g of a substance by 1.00 K. b. the quantity of heat needed to change the temperature of 1.00 g of a substance by K. c. the mass of a substance that 1.00 J of energy will heat by 1.00 K. d. the temperature change undergone when 1.00 g of a substance absorbs J. e. the maximum amount of heat that 1.00 g of a substance may absorb without decomposing. 3

13. Identify the point(s) on the following diagram where the addition of heat will cause some of the sample to melt. a. E, F, and G b. A, B, and C c. B, C, and D d. G and H e. B and C 14.

5 13. Identify the point(s) on the following diagram where the addition of heat will cause some of the sample to melt. a. E, F, and G b. A, B, and C c. B, C, and D d. G and H e. B and C 14. Calculate the energy in the form of heat (in kj) required to change 50.0 g ice at 15.0 C to liquid at 65.0 C. (Heat of fusion = 333 J/g; heat of vaporization = 2256 J/g; specific heat capacities: ice = 2.06 J/g K, liquid water = J/g K) a kj b kj c kj d. 128 kj e. 145 kj 15. Which of the following statements is CORRECT? a. If a reaction occurs at constant pressure, w = E. b. If a reaction occurs at constant pressure, q = H. c. If a reaction occurs at constant pressure, q = E. d. If a reaction occurs at constant volume, E > H. e. If a reaction occurs at constant volume, w = E. 4

6 16. When H 2 S(g) reacts with O 2 (g) according to the following combustion reaction, 518 kj of energy are evolved for each mole of H 2 S(g) that reacts. Complete the following thermochemical equation. 2H 2 S(g) + 3O 2 (g) 2H 2 O(g) + 2SO 2 (g) H =? a. 518 kj b kj c kj d kj e kj 17. The thermochemical equation for the combustion of benzene is shown below. 2 C 6 H 6 ( ) + 15 O 2 (g) 12 CO 2 (g) + 6 H 2O(g) r H = kj/mol-rxn What is the enthalpy change for the combustion of 12.5 g C 6 H 6? a. 313 kj b. 626 kj c kj d kj e kj 18. Determine the standard enthalpy change for the reaction: PbO(s) + Hg(l) Pb(s) + HgO (s) given the enthalpies of reaction below. 2 Pb(s) + O 2 (g) 2 PbO(s) H = kj 2 Hg(l) + O 2 (g) 2 HgO (s) H = kj a kj b kj c kj d kj e kj 19. Which of the following chemical equations corresponds to the standard molar enthalpy of formation of SO 3? a. SO 2 (g) + 1/2 O 2 (g) SO 3 (g) b. 2 SO 2 (g) + O 2 (g) 2 SO 3 (g) c. S 8 (s) + 12 O 2 (g) 8 SO 3 (g) d. 2 S(s) + 3 O 2 (g) 2 SO 3 (g) e. 1/8 S 8 (s) + 3/2 O 2 (g) SO 3 (g) 5

7 Name_ ABCDEG Part II. 10 points per question For full credit, you must show all conversion factors and the final answer with complete units, use the correct number of significant figures, and round off correctly. WRITE CLEARLY: if the grader cannot read your writing, no credit will be assigned. Question 21 Iron reacts with hydrochloric acid. Fe(s) + 2 HCl(aq) ---> FeCl 2 (aq) + H 2 (g) What volume of 2.55 M HCl(aq) will react with 35.0 g Fe(s)? 6

8 Name_ ABCDEG Question 22 A g sample of ethanol, CH 3 CH 2 OH, is combusted in a bomb calorimeter. The temperature of the calorimeter increases by C. If the heat capacity of the bomb is J/ C and it contains 1150 g of water, what is the enthalpy change per mole of ethanol combusted? (The specific heat capacity of water is J/g C and the molar mass of ethanol is g/mol.) 7

Avogadro s number = 6.0221 x 10 23 1 in = 2.

9 Avogadro s number = x in = cm 1 amu = x g 1 mile = ft 8

10 Scratch paper (please detach carefully). 9

Please take a seat in Row Seat according to the following map

Please take a seat in Row Seat according to the following map ABCDEG Name Practice Chem 105X Fall 2009 Keller Hour Exam 2 Chap 3 &4 Kotz Please take a seat in Row_ Seat_ according to the following map Please: Keep this booklet closed until instructed to open it.