CHE 107 Summer 2018 Exam 1

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1 CHE 107 Summer 2018 Exam 1 Your Name: Your ID: Question #: 1 Which theory correctly predicts the number of unpaired electrons in O2?. A. valence bond theory of hybridized orbitals B. Lewis electron dot theory C. molecular orbital theory D. resonance theory Question #: 2 Which statement is true? A. Bonding molecular orbitals are higher in energy than the atomic orbitals combined to form them. B. Combinations of bonding molecular orbitals produce a valence band. C. Antibonding molecular orbitals are more stable than the atomic orbitals combined to form them. D. Three molecular orbitals will result from the triangular combination of three atomic orbitals.

2 Question #: 3 A. B. C. D. Fill in each blank with a letter [A, B, C, or D] that would represent the electron density for A sigma antibonding (σ*) molecular orbital 1 A pi bonding ( ) molecular orbital 2 2.

3 Question #: 4 Using the empty MO diagram below, we can predict that O2 2 will contain a bond and be. A. double; paramagnetic B. single; diamagnetic C. double; diamagnetic D. single; paramagnetic Question #: 5 In the diagram below, material C is a/an: A. conductor B. semi-conductor C. insulator D. dopant

4 Question #: 6 To prepare an n-type semiconductor, a crystal of 1 [arsenic, gallium, germanium] is doped with a trace amount of 2 [boron, indium, phosphorus]. 2. Question #: 7 The figure below is of a 1 [simple, body-centered, face-centered] cubic unit cell where the 2 [atoms per unit cell, coordination number, packing efficiency] is twelve. 2.

5 Question #: 8 Which metal will crystallize with the most empty space in the unit cell? A. chromium, body-centered cubic B. cobalt, hexagonal closest-packed C. copper, face-centered cubic Question #: 9 Scroll down to examine the three structures below. How much does each red ion contribute to the unit cell? Enter 1, 1/2, 1/4, 1/8, as appropriate. Each red ion = 1 ion. Each red ion = 2 ion.

6 Each red ion = 1 ion. Each red ion = 3 ion Question #: 10 Tungsten (184 g/mol) crystallizes in a body-centered cubic unit cell with an edge length of 317 pm. What is the density, in g/cm 3, of a tungsten unit cell? 1 g/cm 3 Report your answer with three significant figures. Do NOT include units with your answer.

7 Question #: 11 Fluorite, a crystalline solid that contains eight yellow fluoride ions entirely within the unit cell, gray calcium ions on all the corners, and gray calcium ions on all the faces, contains a total of 1 calcium ions and 2 fluoride ions. The correct formula unit for this crystalline unit cell is Ca 3 F 4. Enter whole number answers in each blank. If the answer is 1, fill in Question #: 12 A piece of metal at 85 C is added to water at 25 C. The final temperatures of both the metal and the water are 30 C. Which statement is true? A. qmetal >qwater B. qmetal < qwater C. qmetal = qwater D. qmetal = qwater

8 Question #: 13 A block of aluminum releases 7350 J of heat as it cools down by 54 ºC. What is the mass, in grams, of the aluminum block? The specific heat of aluminum is J/g ºC. 1 g Report your answer with three significant figures. Do NOT include units with your answer. Question #: 14 What is the final temperature when a 20.0 g sample of water, initially at 23.0 C, absorbs 975 J of heat? The specific heat of water is 4.18 J/g C. 1 C Report your answer with three significant figures. Do NOT include units with your answer. Question #: 15 It was determined that an 18.0-gram sample of the alloy required 1264 J of heat to raise the temperature of the alloy by 54.1 C. What is the specific heat of the alloy? Cs = 1 J/g ºC Report your answer with three significant figures. Do NOT include units in your answer.

9 Question #: 16 A 4.75 g sample of lead is warmed to 95.0ºC and submerged in 35.0 g of water initially at 20.4ºC. What is the final temperature of the mixture? 1 ºC Specific heat capacity of lead = J/g ºC Specific heat capacity of water = J/g ºC Enter your answer with three significant figures. Do NOT include units in your answer. Question #: 17 What is the change in heat when g of calcium metal is completely reacted according to the following chemical reaction? 2 Ca(s) + O2(g) 2 CaO(s) ΔH = kj. A kj B. 80 kj C. 635 kj D kj Question #: 18 The combustion of glucose, C6H12O6, (180. g/mol) is described by the equation: C6H12O6(s) + 6 O2(g) 6 CO2(g) + 6 H2O(l); where ΔH rxn= 2820 kj. How many grams of glucose need to combust completely to release Joules of heat? Report your answer with three significant figures. Do NOT include units in your answer. 1 grams

10 Question #: 19 How much energy is required to convert 23.0 g (0.500 mol) of solid ethanol, CH3CH2OH(s), at 154 C, to liquid ethanol, CH3CH2OH(l), at 114 C?. melting point boiling point ΔHfus ΔHvap Cs of CH3CH2OH(s) Cs of CH3CH2OH(l) Cs of CH3CH2OH(g) 114 C 78.4 C 5.02 kj/mol 38.6 kj/mol 0.97 J/g C 2.46 J/g C 0.95 J/g C A kj B kj C kj D kj Question #: 20 A certain process absorbs 385 kj of energy as heat and does 547 kj of work on the surroundings. What is the change in internal energy of the system? 1 kj Report your answer with three significant figures. Include the sign (+ or ). Do NOT include units in your answer.

11 Question #: 21 Calculate the standard enthalpy change (ΔH rxn) for the following reaction: N2H4(l) + 3 O2(g) 2 NO2(g) + 2 H2O(l) using the enthalpies of formation in the table below. ΔH rxn = 1 kj Substance ΔH f (kj/mol) N2H4(l) NO2(g) H2O(l) Question #: 22 Which statement is true? A. Freezing is an endothermic process. B. Sublimation is an endothermic process. C. When a solid is heated to its melting point, the temperature of the solid continues to rise while the substance melts. D. The heat of fusion of a substance is generally larger than its heat of vaporization. Question #: 23 Dissolving 4.20 g of Ba(OH)2 in 450. ml of water causes the temperature of the solution to increase by from 22.3 C to 42 C. Determine ΔH per mol of Ba(OH)2 for the reaction. Ba(OH)2(s) Ba 2+ (aq) + 2 OH (aq). The specific heat of the solution is 4.18 J/g C The density of water is 00 g/ml. The calorimeter absorbs no significant amount of heat. A kj/mol B kj/mol C kj/mol D kj/mol

12 Question #: 24 Which one is the balanced chemical equation for ΔHf for CH3COOH(g)?. A. CH3COOH(g) 2 C(s) + 2 H2(g) + O2(g) B. 2 C(s) + 2 H2(g) + O2(g) CH3COOH(g) C. CH3COOH(g) + 2 O2(g) 2 CO2(g) + 2 H2O(g) D. 2 CO(g) + 2 H2(g) CH3COOH(g) Question #: 25 Calculate ΔH rxn for the reaction: CH4(g) + N2(g) HCN(g) + NH3(g) using the following reactions and given ΔH values: 3 H2(g) + N2(g) 2 NH3(g) ΔH 1 = 45.9 kj/mol C(s) + 2 H2(g) CH4(g) ΔH 2 = 74.6 kj/mol HCN(g) ½ H2(g) + C(s) + ½ N2(g) ΔH 3 = kj/mol A kj/mol B kj/mol C kj/mol D kj/mol

13 DRAFT Do Not Use Until Posted. CHE 107 Summer 2018 Exam 1 - Confidential Your Name: Your ID: attachment_for_pubexamuid_lnxp xx_27jpg Question #: 1 Which theory correctly predicts the number of unpaired electrons in O 2?. A. valence bond theory of hybridized orbitals B. Lewis electron dot theory C. molecular orbital theory D. resonance theory Question #: 2 Which statement is true?

A. Bonding molecular orbitals are higher in energy than the atomic orbitals combined to form them. B. Combinations of bonding molecular orbitals produce a valence band. C. Antibonding molecular orbitals are more stable than the atomic orbitals combined to form them.

14 A. Bonding molecular orbitals are higher in energy than the atomic orbitals combined to form them. B. Combinations of bonding molecular orbitals produce a valence band. C. Antibonding molecular orbitals are more stable than the atomic orbitals combined to form them. D. Three molecular orbitals will result from the triangular combination of three atomic orbitals. Question #: 3 A. B. C. D. Fill in each blank with a letter [A, B, C, or D] that would represent the electron density for A sigma antibonding (σ*) molecular orbital 1 A pi bonding ( ) molecular orbital 2 B

15 2. C Question #: 4 Using the empty MO diagram below, we can predict that O 2 2 will contain a bond and be. A. double; paramagnetic B. single; diamagnetic C. double; diamagnetic D. single; paramagnetic Question #: 5 In the diagram below, material C is a/an: A. conductor

16 B. semi-conductor C. insulator D. dopant Question #: 6 To prepare an n-type semiconductor, a crystal of 1 [arsenic, gallium, germanium] is doped with a trace amount of 2 [boron, indium, phosphorus]. germanium 2. phosphorus Question #: 7 The figure below is of a 1 [simple, body-centered, face-centered] cubic unit cell where the 2 [atoms per unit cell, coordination number, packing efficiency] is twelve. face-centered 2. coordination number Question #: 8

Which metal will crystallize with the most empty space in the unit

17 Which metal will crystallize with the most empty space in the unit cell? A. chromium, body-centered cubic B. cobalt, hexagonal closest-packed C. copper, face-centered cubic Question #: 9 Scroll down to examine the three structures below. How much does each red ion contribute to the unit cell? Enter 1, 1/2, 1/4, 1/8, as appropriate. Each red ion = 1 ion. Each red ion = 2 ion. Each red ion = 3 ion.

1/8 2. 1/2 3. 1/4 Question #: 10 Tungsten (184 g/mol) crystallizes in a body-centered cubic unit cell with an edge length of 317 pm. What is the density, in g/cm 3, of a tungsten unit cell?

18 1/8 2. 1/2 3. 1/4 Question #: 10 Tungsten (184 g/mol) crystallizes in a body-centered cubic unit cell with an edge length of 317 pm. What is the density, in g/cm 3, of a tungsten unit cell? 1 g/cm 3 Report your answer with three significant figures. Do NOT include units with your answer Question #: 11 Fluorite, a crystalline solid that contains eight yellow fluoride ions entirely within the unit cell, gray calcium ions on all the corners, and gray calcium ions on all the faces, contains a total of 1 calcium ions and 2 fluoride ions. The correct formula unit for this crystalline unit cell is Ca 3 F 4. Enter whole number answers in each blank. If the answer is 1, fill in

19 Question #: 12 A piece of metal at 85 C is added to water at 25 C. The final temperatures of both the metal and the water are 30 C. Which statement is true? A. q metal >q water B. q metal < q water C. q metal = q water D. q metal = q water Question #: 13 A block of aluminum releases 7350 J of heat as it cools down by 54 ºC. What is the mass, in grams, of the aluminum block? The specific heat of aluminum is J/g ºC. 1 g Report your answer with three significant figures. Do NOT include units with your answer. 152 Question #: 14 What is the final temperature when a 20.0 g sample of water, initially at 23.0 C, absorbs 975 J of heat? The specific heat of water is 4.18 J/g C. 1 C Report your answer with three significant figures. Do NOT include units with your answer. 34.7

20 Question #: 15 It was determined that an 18.0-gram sample of the alloy required 1264 J of heat to raise the temperature of the alloy by 54.1 C. What is the specific heat of the alloy? C s = 1 J/g ºC Report your answer with three significant figures. Do NOT include units in your answer Question #: 16 A 4.75 g sample of lead is warmed to 95.0ºC and submerged in 35.0 g of water initially at 20.4ºC. What is the final temperature of the mixture? 1 ºC Specific heat capacity of lead = J/g ºC Specific heat capacity of water = J/g ºC Enter your answer with three significant figures. Do NOT include units in your answer Question #: 17 What is the change in heat when g of calcium metal is completely reacted according to the following chemical reaction? 2 Ca(s) + O 2 (g) 2 CaO(s) ΔH = kj. A kj B. 80 kj C. 635 kj D kj Question #: 18

21 The combustion of glucose, C 6 H 12 O 6, (180. g/mol) is described by the equation: C 6 H 12 O 6 (s) + 6 O 2 (g) 6 CO 2 (g) + 6 H 2 O(l); where ΔH rxn = 2820 kj. How many grams of glucose need to combust completely to release Joules of heat? Report your answer with three significant figures. Do NOT include units in your answer. 1 grams Question #: 19 How much energy is required to convert 23.0 g (0.500 mol) of solid ethanol, CH 3 CH 2 OH(s), at 154 C, to liquid ethanol, CH 3 CH 2 OH(l), at 114 C?. melting point 114 C boiling point 78.4 C H fus 5.02 kj/mol H vap 38.6 kj/mol C s of CH 3 CH 2 OH(s) 0.97 J/g C C s of CH 3 CH 2 OH(l) 2.46 J/g C C s of CH 3 CH 2 OH(g) 0.95 J/g C A kj B kj C kj D kj Question #: 20 A certain process absorbs 385 kj of energy as heat and does 547 kj of work on the surroundings. What is the change in internal energy of the system? 1 kj Report your answer with three significant figures. Include the sign (+ or ). Do NOT include units in your answer.

22 -162 Question #: 21 Calculate the standard enthalpy change (ΔH rxn ) for the following reaction: N 2 H 4 (l) + 3 O 2 (g) 2 NO 2 (g) + 2 H 2 O(l) using the enthalpies of formation in the table below. Substance H f (kj/mol) N 2 H 4 (l) NO 2 (g) H 2 O(l) ΔH rxn = 1 kj kj -556kJ kj kJ Question #: 22 Which statement is true? A. Freezing is an endothermic process. B. Sublimation is an endothermic process. C. When a solid is heated to its melting point, the temperature of the solid continues to rise while the substance melts. D. The heat of fusion of a substance is generally larger than its heat of vaporization. Question #: 23 Dissolving 4.20 g of Ba(OH) 2 in 450. ml of water causes the temperature of the solution to increase by from 22.3 C to 42 C. Determine ΔH per mol of Ba(OH) 2 for the reaction. Ba(OH) 2 (s) Ba 2+ (aq) + 2 OH (aq). The specific heat of the solution is 4.18 J/g C The density of water is 00 g/ml. The calorimeter absorbs no significant amount of heat.

23 A kj/mol B kj/mol C kj/mol D kj/mol Question #: 24 Which one is the balanced chemical equation for ΔH f for CH 3 COOH(g)?. A. CH 3 COOH(g) 2 C(s) + 2 H 2 (g) + O 2 (g) B. 2 C(s) + 2 H 2 (g) + O 2 (g) CH 3 COOH(g) C. CH 3 COOH(g) + 2 O 2 (g) 2 CO 2 (g) + 2 H 2 O(g) D. 2 CO(g) + 2 H 2 (g) CH 3 COOH(g) Question #: 25 Calculate ΔH rxn for the reaction: CH 4 (g) + N 2 (g) HCN(g) + NH 3 (g) using the following reactions and given ΔH values: 3 H 2 (g) + N 2 (g) 2 NH 3 (g) H 1 = 45.9 kj/mol C(s) + 2 H 2 (g) CH 4 (g) H 2 = 74.6 kj/mol HCN(g) ½ H 2 (g) + C(s) + ½ N 2 (g) H 3 = kj/mol A kj/mol B kj/mol C kj/mol D kj/mol

CHE 107 Fall 2017 Exam 1

CHE 107 Fall 2017 Exam 1 Your Name: Your ID: Question #: 1 Fill in the blanks with the letter corresponding to the correct term. Use each term only once. Your response for each one should be a single letter.