H N C C H C N N C H C H H

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1 OUR EXAM II Page 1 1. Which of the following statements about hybrid orbitals is true? a. Valence atomic orbitals always combine with inner core atomic orbitals to produce hybrid orbitals. b. The orientation in space of the hybrid orbitals is identical to the orientation in space of the atomic orbitals from which they are formed. c. An sp 2 hybrid orbital from one atom can overlap to form a bond with an sp 3 hybrid orbital from another atom. d. Overlap of hybrid orbitals form π bonds. e. Atoms which are sp 2 hybridized form 2 pi bonds. 2. A widely used herbicide is atrazine, C8N5Cl14, whose skeletal structure is shown below. Complete a Lewis structure for this organic compound. C C N C 1 C N N C N C N C C Cl Which of the following statements concerning the Lewis structure for atrazine is false? a. Atrazine has zero atoms which are sp hybridized. b. Eight of the carbon and nitrogen atoms in atrazine have at least one unhybridized p atomic orbital. c. There are 28 sigma (σ) bonds and 3 pi (π) bonds in the Lewis structure. d. The nitrogen atom labeled 1 is sp 3 hybridized. e. All the carbon-hydrogen bonds in atrazine are formed from overlap of sp 3 hybrid orbitals from carbon with 1s orbitals from hydrogen. 3. You find a bottle on the shelf in the Chem 103 lab. The label says 0.10 M MgSO4. Which of the following statements best describes what is in the bottle? a. The MgSO4 is a solid on the bottom of the bottle because it is not soluble in water. b. There are MgSO4 molecules floating around in solution. c. There are magnesium ions, sulfur ions, and oxygen ions floating around in solution. d. There are magnesium ions and sulfate ions floating around in solution.

2 OUR EXAM II Page 2 4. A solution of 1.0 M KBr is diluted. Which of the following happens during the dilution? a. molarity increases; volume is constant; moles of KBr decrease b. molarity increases; volume increases; moles of KBr is constant c. molarity decreases; volume decreases; moles of KBr is constant d. molarity decreases; volume increases; moles of KBr is constant e. molarity increases; volume is constant; moles of KBr increase 5. When aluminum metal is heated with an element from Group 6A of the periodic table, an ionic compound forms. When the experiment is performed with an unknown Group 6A element, the product is 18.55% Al by mass. What is the formula of the compound? a. AlS3 b. Al2S3 c. Al2Se3 d. Al2Te3 e. Al3S2 6. Which of the following gas samples (a-d) has/have the largest average kinetic energy and has/have the fastest average velocity for the gas molecules in the gas sample? a. 1.0 mol of CO2(g) at P = 1.0 atm and T = 0. C b. 1.0 mol of F2(g) at P = 1.0 atm and T = 0. C c. 1.0 mol of N2(g) at P = 1.0 atm and T = 100. C d. 1.0 mol of Cl2(g) at P = 1.0 atm and T = 100. C e. The gas samples in answers c and d both have the same average kinetic energy and have the same average molecular velocity. 7. Consider 2 different containers each filled with two moles of Ne(g). One of the containers is rigid and is of constant volume; the other container is flexible (like a balloon) and is capable of changing its volume in order to keep the external pressure and internal pressure equal to each other. If you raise the temperature in both containers, which of the following is true concerning the pressure and density of the gas inside each container? Assume a constant external pressure. a. Rigid container: Pressure and density both increase; Flexible container: Pressure and density are both constant. b. Rigid container: Pressure is constant, density decreases; Flexible container: Pressure increases, density decreases. c. Pressure increases and density is constant in both containers. d. Rigid container: Pressure increases, density decreases; Flexible container: Pressure increases, density is constant. e. Rigid container: Pressure increases, density is constant; Flexible container: Pressure is constant, density decreases.

3 OUR EXAM II Page 3 8. Consider the following balanced reaction: 2 C36(g) + 2 N3(g) + 3 O2(g) 2 C33N(g) + 6 2O(g) When 5.0 mol of C36, 5.0 mol of N3 and 6.0 mol of O2 are reacted, 3.0 mol of C33N are actually produced. What is the percent yield of the reaction? a. 33% b. 50.% c. 60.% d. 67% e. 75% 9. Consider a classroom containing ten evenly-spaced rows of students. If a student in row 1 releases laughing gas (N2O) and a student in row 10 simultaneously releases a lachrymator (a gas which causes tears) with molar mass 176, in which row do the students first laugh and cry at the same time? int: the molar mass of the lachrymator is 4 times greater than the molar mass of N2O, i.e., molar mass lachrymator = 4 molar mass N2O. a. row 2 b. row 3 c. row 7 d. row 8 e. row Bismuth aluminate (Al6Bi2O12) is a medication used to treat upset stomachs. If mg of bismuth aluminate is digested, calculate the mass of bismuth consumed. Bi is element #83 and the molar mass of Al6Bi2O12 is g/mol. a g b g c g d g e g 11. Consider an organic compound which contains only carbon, hydrogen, and oxygen. Combustion of g of the compound yields g CO2 and 4.37 g 2O. What is the mass percent of hydrogen in this compound? a. 3.87% b. 2.98% c. 5.67% d. 3.23% e. 4.58% 12. Consider an organic compound which contains only carbon, hydrogen, and oxygen. Combustion of g of the compound yields g CO2 and 4.37 g 2O. If the molar mass of the compound is between 250 g/mol and 280 g/mol, which of the following is the molecular formula? a. C34O3 b. C23O4 c. C1218O6 d. C912O9 e. C69O12

4 OUR EXAM II Page Silver sulfadiazine burn-treating cream creates a barrier against bacterial invasion and releases antimicrobial agents directly into the wound. If 25.0 g of Ag2O (molar mass = g/mol), is reacted with 50.0 g of C1010N4SO2 (molar mass = g/mol), what mass of silver sulfadiazine, AgC109N4SO2 (molar mass = g/mol), can be produced assuming 100% yield? Ag2O + 2 C1010N4SO2 2 AgC109N4SO2 + 2O a g b g c g d g e g 14. At elevated temperatures, sodium chlorate decomposes to produce sodium chloride and oxygen gas. A g sample of impure sodium chlorate was heated until the production of oxygen gas ceased. The oxygen gas collected over water occupied 57.2 ml at a temperature of 22 C and a total pressure of 734 torr. Calculate the mass percent of NaClO3 in the original sample. At 22 C, the vapor pressure of water is 19.8 torr and assume 100% yield in the reaction. a. 18.0% b. 46.7% c. 62.2% d. 75.0% e. 87.1% 15. A roach killer, dibutyl succinate, was analyzed and found to be composed of 62.58% C, 9.63% and 27.79% O. What is the empirical formula of dibutyl succinate? a. C35O b. C611O2 c. C59O3 d. C812O6 e. C46O ml of 5.50 M KO are required to react completely with 22.0 ml of an 2SO3 solution. What is the molarity of the 2SO3 solution? 2SO3 is a diprotic acid. a M b M c M d M e M 17. Which of the following statements is false? a. In XeF4, the central Xe atom is sp 3 hybridized. b. In SF6, the central S atom is d 2 sp 3 hybridized. c. In PCl5, the central P atom is dsp 3 hybridized. d. In CO2, the central C atom is sp hybridized. e. In SO3, the central S atom is sp 2 hybridized.

5 OUR EXAM II Page On a typical August day in Champaign, the temperature is 35 o C and the relative humidity is 90%. A 10.0 L sample of air on this 35 C day contains g of 2O(g). From this data, calculate the partial pressure of water on a 35 C day having a relative humidity of 90%. a torr b torr c torr d torr e. 684 torr Consider the following information for the next three questions ml of M lead(ii) nitrate is added to 75.0 ml of M ammonium phosphate and a precipitate forms. 19. Which of the following is the correct net ionic equation for the precipitation reaction? a. 3 Pb 2+ (aq) + 2 PO4 3 (aq) Pb3(PO4)2(s) b. Pb 2+ (aq) + PO4 2 (aq) PbPO4(s) c. Pb 2+ (aq) + 2 PO4 (aq) Pb(PO4)2(s) d. N4 2+ (aq) + 2 NO3 (aq) N4(NO3)2(s) e. N4 + (aq) + NO3 (aq) N4NO3(s) 20. ow many moles of precipitate form assuming 100% yield? a mol b mol c mol d mol e mol 21. Calculate the molarity of the ammonium ions after precipitation is complete. a M b M c M d M e M 22. A compound or ion has delocalized electrons resulting in equivalent bonds to oxygen. All of the bonds in this compound or ion are stronger than single bonds yet are significantly weaker than double bonds. Which of the following could be this compound or ion? a. CO2 b. NO2 + c. SO3 2 d. NO3 e. XeO3

6 OUR EXAM II Page Under which of the following conditions will a sample of SO2(g) behave most ideally? a. 40 K, 500 atm b K, 0.50 atm c. 40 K, 0.50 atm d K, 500 atm 24. When N2(g) reacts with F2(g), NF3(g) is produced. If 1.0 L of F2(g) is reacted with an excess of N2(g), how many moles of NF3(g) can be produced at STP? a mol b mol c mol d mol e mol 25. An ideal gas in a flexible container occupies a volume of 10.0 L at 38 o C and 0.20 atm. If the gas sample is cooled to 7 o C and the volume is decreased to 3.60 L, what is the new pressure of the gas sample? a. 1.7 atm b atm c atm d atm e atm 26. Rank the following three substances from weakest to strongest electrolyte. NO3, C1222O11, C23O2 a. C1222O11 < C23O2 < NO3 b. C1222O11 < NO3 < C23O2 c. C1222O11 < NO3 C23O2 d. NO3 < C23O2 < C1222O11 e. C23O2 < C1222O11 < NO3 27. Lithium and nitrogen react to form lithium nitride. What mass of lithium nitride can be produced when 20.0 g of Li is reacted with excess nitrogen? a g b g c g d g e. 121 g 28. Saccharin has a molecular formula of C75NO3S. A g mixture containing saccharin and glucose was dissolved in water. The saccharin in the mixture was reacted to convert all of the sulfur in saccharin into the sulfate ion. The sulfate ion was then precipitated by adding an excess of barium chloride solution. The mass of BaSO4 obtained was g. What is the mass percent of saccharin in the mixture? The molar mass of saccharin is g/mol, the molar mass of glucose (C612O6) is g/mol, and the molar mass of BaSO4 is g/mol. a. 75.0% b. 67.0% c. 50.0% d. 33.0% e. 25.0%

7 OUR EXAM II Page Which of the following statements does not describe the reaction pictured below? a. and combine in a 2:1 mole ratio. b. is the limiting reactant. c. The reaction produces two different products. d. The reactants pictured both represent diatomic elements. 30. Consider a container holding a real gas at some temperature and pressure, i.e., the gas is not behaving ideally. Which of the following is true regarding the measured pressure and the measured volume of the real gas as compared to the pressure and the volume of the container if the gas were behaving ideally? int: look at the van der Waals equation given on the constants/equations page of this exam. a. Pmeasured > Pideal; Vmeasured > Videal b. Pmeasured > Pideal; Videal > Vmeasured c. Pideal > Pmeasured; Vmeasured > Videal d. Pideal > Pmeasured; Videal > Vmeasured 31. My answers for this Chemistry 102 exam should be graded with the answer sheet associated with: a. Form A b. Form B c. Form C d. Form D e. Form E

Exam 2, Ch 4-6 October 12, Points

Exam 2, Ch 4-6 October 12, Points Chem 130 Name Exam 2, Ch 4-6 October 12, 2016 100 Points Please follow the instructions for each section of the exam. Show your work on all mathematical problems. Provide answers with the correct units