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CH141 – Practice Problems/Practice Final Exam

Page 1 of 12 Name: _______________________

1. What is the SO42- concentration of a solution prepared by dissolving 3.00 g of Na2SO4 in 1.00 L of water?

2. What is the hybridization state of the nitrogen atom in the molecule NH3? Explain your answer.

3. Name the following compounds: a) SiO2 _____________________________________ b) BaCO3______________________________________ 4. Write the chemical formula for the following compounds: a) cadmium (II) sulfide ________________________ b) potassium perchlorate ________________________ 5. Classify the following compounds as strong, weak, or nonelectrolytes: a) NaI ___________________________ b) NaC2H3O2 _______________________ c) NH3 ____________________________ d) CaCO3 _____________________________ 6. Place the following elements in order of increasing atomic radii: Mg, Na, Rb, Cl.

CH141 – Practice Problems/Practice Final Exam

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7. What is the oxidation state of the bold element in each compound below? a) FeCl2

___________________

b) Na2SO3

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c) H2O2

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d) Na3PO4

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8. Place the following diatomic molecules in order of increasing polarity: CN, CF, O2

9. Draw a plot of pressure vs. moles of gas for an ideal gas (label the axes, including units).

10. Circle the correct answer for each of the following: a) the lowest electronegativity: F, Cl, P b) would be most likely to form a stable anion with a –2 charge: Se, Cl, Mg c) is diamagnetic: F, Fe3+, Na+ 13. Like all carbonates, barium carbonate can be decomposed to the metal oxide and CO2. BaCO3 (s) à BaO (s) + CO2 (g) If the ΔHrxn of barium carbonate decompostion is 269.3 kJ/mol, how many kJ are required to decompose 10.0 g of BaCO3?

CH141 – Practice Problems/Practice Final Exam

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12. Using a molecular orbital (MO) diagram, determine the bond order and magnetic properties of the following diatomic molecules: CN, CN+, and CN–. A template of the valence MO’s is given below. Which of the three species is most stable?

σ∗ 2p π* 2p σ2p π2p σ∗ 2s σ2s

13. Draw a Lewis structure for the carbonate ion (CO3 –2). Propose a hybridization and bonding scheme that explains the geometry and bond order for carbonate.

14. Balance the following redox reaction. NH3(g) + O2(g) à NO(g) + H2O(g)

CH141 – Practice Problems/Practice Final Exam

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15. Determine the molar concentration HBr in a 48.0% by mass aqueous HBr solution. (solution density = 1.50 g/cm3)

16. A 0.598 g sample of a green metal carbonate, containing unknown metal M, was heated to give the metal oxide and 0.222 g of CO2 (g) according to the reaction below. MCO3 à MO(s) + CO2(g) What is the metal M? Prove your answer with appropriate calculations.

17. An excess of NaOH is treated with 1.12 liters of HCl gas measured at STP. What weight of sodium chloride is formed? (The reaction runs to completion)

18. For each of the following molecules; a) draw a correct Lewis structure, b) describe the molecular geometry and polarity, and c) give the hybridization on the central atom. a) SCl2 b) NO2- (N is central atom)

CH141 – Practice Problems/Practice Final Exam

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19. The dirigible Hindenberg had a gas volume of 1.4 x 108 liters, and was filled with H2. How much energy was released when the hydrogen completely burned to form gaseous water? (Assume that it was filled to a pressure of 1 atm and at 0 °C.) The heat of formation for gaseous water (steam) is –242 kJ/mol.

20. Write the total ionic equation for the mixing of Ni(NO3)2 (aq) and Na2S (aq).

21. Based on the following redox (balanced) reaction: MnO2 (s) + 2 I– (aq) + 4 H+ (aq) à I2 (aq) + Mn2+ (aq) + 2 H2O(l) a) The reducing agent is _______________________ b) The number of electrons transferred per mole of reaction is _____________________ 22. Under what conditions is the internal energy change of the system (ΔE) equal to the heat flow (q) for a chemical reaction?

23. Carbon dioxide gas diffuses through a porous barrier at a rate of 0.20 mL/minute. If an unknown gas diffuses through the same barrier at a rate of 0.313 mL/minute, what is the molar mass of the unknown gas?

CH141 – Practice Problems/Practice Final Exam

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24. Ethylenediamine has an empirical formula of NH2CH2. Assume that 95 mg of ethylenediamine in the gas phase has a pressure of 235 mmHg in a 125 mL flask at 25 oC. What is the molecular formula of ethylenediamine?

25. The combination of coke and steam produces a mixture called coal gas, which can be used as a fuel or as a starting material for other reactions. The equation for the production of coal gas is 2 C(s) + 2 H2O(g) à CH4 (g) + CO2 (g) Determine the standard enthalpy change for this reaction based on the following standard enthalpies of reaction: C(s) + H2O(g) à CO(g) + H2 (g)

ΔH = +131.3 kJ

CO(g) + H2O(g) à CO2 (g) + H2 (g)

ΔH = –41.2 kJ

CH4 (g) + H2O(g) à 3H2 (g) + CO(g)

ΔH = +206.1 kJ

26. What are the assumptions behind the concept of an ideal gas?

CH141 – Practice Problems/Practice Final Exam

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27. Essence of skunk has a formula of C4H10S. The material making up lemon smell has a formula C10H16. If Prof. King opens bottles of each in the front of the room, which odor will reach you first (assume they are both in the gas phase). How much faster will the winning odor reach you (express your answer as a ratio)?

28. Explain how a barometer works.

29. You generate hydrogen gas by reacting zinc with HCl to produce hydrogen gas and zinc dichloride. You collect the hydrogen gas in an evacuated container with a volume of 3.0 L. If you start with 6.0 grams of zinc and sufficient HCl to complete the reaction, what is the final pressure of the gas collected in the container if the temperature is 25 °C?

30. The total pressure is 5.11 atmospheres for a gas mixture that consists of 0.307 moles of carbon dioxide and an unknown quantity of methane (CH4) in a 2.59 liter container at 27.0 °C. How many grams of methane are in this mixture?

CH141 – Practice Problems/Practice Final Exam

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31. Place the following elements in order of increasing first ionization energy: Mg, Na, Rb, Cl.

32. The standard molar enthalpy of combustion for ethanol, C2H5OH, is -1409 kJ. C2H5OH (g) + 3 O2 (g) à 2 CO2 (g) + 3 H2O (aq) What is the standard enthalpy change for the following process? 4 CO2 (g) + 6 H2O (aq ) à 2 C2H5OH (g) + 6 O2 (g)

33. When one mole of benzene is vaporized at a constant pressure of 1.00 atm and at its boiling point of 353.0 K, 30.79 kJ of energy (heat) is absorbed and the volume change is +28.90 L. What is ∆E for this process? (1 L-atm = 101.3 J)

CH141 – Practice Problems/Practice Final Exam

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34. Refer to the phase diagram for CO2, below a. Label the four regions of the phase diagram with the appropriate phase (solid, liquid, gas, supercritical fluid). b. Indicate the approximate temperature and nature of each phase change that will occur as you heat a sample of CO2 from -100 to 40 oC at a constant pressure of 20.3 atm. c.

Label on the figure and define the critical and triple points. critical point definition: triple point definition:

Phase Diagram for CO2 35. How much heat (in joules) is required to convert a 100 cm3 block of solid CO2 into gaseous CO2 (ΔHsub = 24.2 kJ/mole, density = 1.56 g/cm3)?

CH141 – Practice Problems/Practice Final Exam

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36. A compound containing carbon, nitrogen, and hydrogen is combusted completely with excess oxygen to produce 138 g of NO2, 28.0 g of CO2, and 90.0 g of H2O. What is the empirical formula of the compound?

37. The fluorocarbon compound C2Cl3F3 has a normal boiling point of 47.6 °C. The specific heats of C2Cl3F3 (l) and C2Cl3F3 (g) are 0.91 J/g⋅K and 0.67 J/g⋅K, respectively. The heat of vaporization for the compound is 27.49 kJ/mol. Calculate the heat required to convert 54.0 g of C2Cl3F3 from a liquid at 10.85 °C to a gas at 87.40 °C.

38. Which type of intermolecular attractive force operates between all molecules? dipole-dipole

ion-dipole 

London dispersion

hydrogen-bonding

39. Hydrazine (NH2NH2), hydrogen peroxide (H2O2), and water (H2O) all have exceptionally high surface tensions in comparison with other substances of comparable molecular weights. What structural property do these substances have in common, and how might that account for the high surface tensions?

40. Name the phase transition in each of the following situations, and indicate whether it is exothermic or endothermic. Bromine vapor turns to bromine liquid as it is cooled. Crystals of iodine disappear from an evaporating dish as they stand in a fume hood. Rubbing alcohol in an open container slowly disappears. Molten lava from a volcano turns into solid rock.

CH141 – Practice Problems/Practice Final Exam

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41. Refer to the figure, and describe all the phase changes that would occur in each of the following cases. Water vapor originally at 0.001 atm and 40 °C is slowly compressed at constant temperature until the final pressure is 20 atm.

Water originally at 100.0 °C and 0.10 atm is cooled at constant pressure until the temperature is –100.0 °C.

42. Two pans of water are on different burners of a stove. One pan of water is boiling vigorously, while the other is boiling gently. What is the relationship between the temperatures of the water in the two pans?

43. A large container of water and a small container of water are at the same temperature. What is the relationship between the relative vapor pressures of the water in the two containers?

CH141 – Practice Problems/Practice Final Exam

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44. Calculate the mass percentage of Na2SO4 in a solution containing 10.6 g Na2SO4 in 482 g of water.

45. What is the molality of a solution formed by dissolving 1.14 mol of KCl in 16.0 mol of water?

46. Arrange the following aqueous solutions, each 10% by mass in solute, in order of decreasing boiling point: glucose (C6H12O6), sucrose (C11H22O11), sodium nitrate (NaNO3)....