chem review

15. Calculate the mass of solute in the following solution: 50.0 mL of 0.0300 M C12H22O11.

0.513g

16. When 20.0 grams of an unknown compound are dissolved in 500. grams of benzene, the freezing point of the resulting solution is 3.77C. The freezing point of pure benzene is 5.444C, and the Kf for benzene is 5.12C/m. What is the molar mass of the unknown compound?

120 g/mol

11. The equation relating Kp and Kc is _____. A) Kp = Kc (RT)n B) Kp = Kc RTn C) Kc = Kp RTn D) Kc = Kp (RT)n

A

25. Which of these properties indicate strong intermolecular forces of attraction (may be more than one) A. High Enthalpy of evaporation B. High Enthalpy of fusion C. High Melting point D. High Volatility (how easy it is to evaporate a liquid at a given temperature) E. High Vapor pressure at a given temperature F. High Boiling point G. High Polarizability H. High Surface tension I. High Critical temperature

A,B,C,F,G,H,I

31. What is the main reason that water has an unexpectedly high boiling point? (a) Water is a polar molecule. (b) The existence of hydrogen bonding. (c) London dispersion forces. (d) Ionic bonding (e) None of the above.

B

33. How much heat (in KJ) is needed to convert 866 g ice (-10oC) to steam at 126oC? Specific heats of ice and steam are 2.03 J/g x oC and 1.99 J/g x oC respectively, for liquid water is 4.184 J/g x oC Heat of fusion of water: 6010 Joule/mol, Molar Heat of Evaporation of Water: 4.097x10 6 Joule/mol)

2.67 x 10^6 J

1. In the following table: Element X Boiling Point (K) He 4.4 Ne 27.3 Ar 87.4 Kr 122 Xe 167 Rn 202 The increase in boiling points observed is due to: a) increasing polarizability b) Stronger Hydrogen bond interaction c) Stronger chemical bonds in the X2 molecule d) Increasing lattice energy e) Increasing dipole moment

A

17. Which of the following responses arranges interactions in order of increasing strength? ("permanent" is used to indicate non-H-bonding permanent dipole-permanent dipole interactions), London forces, hydrogen bonds, permanent dipole-dipole interactions (a) London <permanent dipole <hydrogen (b) hydrogen <permanent dipole < London (c) London <hydrogen <permanent dipole (d) hydrogen <permanent dipole <London (e) hydrogen <London <permanent dipole

A

18. Which response includes all of the following substances in which London forces are the most significant factors in determining boiling points, and no other substances? I. Cl2 II. HF III. Ne IV. KNO2 V. CCl4 (a) I, III, and V (b) I, II, and III (c) II and IV (d) II and V (e) III, IV, and V

A

2. A phase diagram is the plot of _____. A) P vs T B) V vs T C) P vs V D) 1/P vs. T

A

22. Which of the following statements is correct? a. Hypertonic solutions cause blood cells to shrink b. Hypertonic solutions cause blood cells to expand c. Isotonic solutions cause blood cells to expand d. Hypotonic solutions cause blood cells to shrink

A

23. Which of the following reaction rates is the highest? a. Initial rate b. Average rate c. Final rate d. Instantaneous rate

A

24. The rate of disappearance of NO in the reaction 2NO + O2 2NO2 is 0.066 Ms-1. The rate of formation of NO2 is _____ Ms-1. a. 0.066 b. 0.132 c. 0.033 d. 0.66

A

24. Which one of the following has the highest heat of vaporization? (a) CH3NH2 (b) CH4 (c) C2H6 (d) SiH4 (e) H2S

A

26. The rate of reaction of N2 in the reaction N2 + 3H2 2NH3 is 0.025Ms-1. The rate at which hydrogen reacts will be _____ Ms-1 a. 0.075 b. 0.025 c. 0.050 d. 0.100

A

27. Which one of the following melts at the lowest temperature at a given pressure? (a) CH4 (b) LiC (c) C10H8 (d) CaCl2 (e) H2O

A

29. A catalyst does not change the ______ of the reaction. a. mechanism b. enthalpy c. energy of activation d. rate

A

29. How does increased pressure affect the boiling point? (a) The boiling point rises. (b) The boiling point stays the same. (c) The boiling point is lowered. (d) The boiling point is dependent on temperature so it would rise only no matter what the pressure. (e) none of the above

A

30. Dipole-dipole attraction results from (a) the electrostatic attraction of the positive end of one polar molecule for the negative end of another. (b) the positive ends of two molecules repelling each other, pushing the molecules into others. (c) the electrostatic attraction of the positive end of one polar molecule for the positive end of another. (d) the attraction between an anion and a cation within a molecule. (e) none of the above.

A

32. Which of the following statements is false? A. A catalyst increases the rate of the forward reaction, but does not alter the reverse rate. B. A catalyst alters the mechanism of reaction. C. A catalyst alters the activation energy. D. A catalyst may be altered in the reaction, but is always regenerated. E. A catalyst increases the rate of reaction, but is not consumed.

A

6. What is the molarity of a solution of 10% by mass cadmium sulfate, CdSO4 (molar mass = 208.46 g/mol) by mass? The density of the solution is 1.10 g/mL. A. 0.528 M B. 0.436 M C. 0.479 M D. 0.048 M E. 22.9 M

A

13. Connect the numbers with the proper letters A Ionic Solids 1 Hard to soft, conduct electricity as solids and liquids B: Covalent solids 2 Generally hard, non conductors of electricity, molten or solid C: Molecular Solids 3 Hard and brittle, conduct electricity in the melt but not solid D: Metallic solids 4 Hard to soft, non conductors of electricity no matter the state

A3,B2,C4,D1

1. A liquid having a higher vapor pressure will have _____. A) higher molecular weight B) lower boiling point C) higher boiling point D) higher surface area

B

10. The solubility of gases in water usually decreases with A. increasing pressure. B. increasing temperature. C. decreasing temperature.

B

12. Kp will be equal to Kc if _____. A) n = 1 B) n = 0 C) RT = 0 D) n =

B

13. Arrange the following aqueous solutions in order of increasing boiling points. 0.050 m Mg(NO3)2; 0.100 m ethanol; 0.090 m NaCl A. Mg(NO3)2 < NaCl < ethanol B. ethanol < Mg(NO3)2 < NaCl C. ethanol < NaCl < Mg(NO3)2 D. NaCl < ethanol < Mg(NO3)2 E. Mg(NO3)2 < ethanol < NaCl

B

19. The molality of 30 g NH3 dissolved in 70 g of water is _____. a. 17.3 m b. 25.2 m c. 10.5 m d. 36.0 m

B

21. Which response includes all of the following compounds that exhibit hydrogen bonding and no other compounds? CH4, AsH3, CH3NH2, H2Te, HF (a) AsH3, H2Te (b) CH3NH2, HF (c) CH4, AsH3, H2Te (d) AsH3, CH3NH2 (e) HF, H2Te

B

27. A catalyst increases the rate of the reaction by ______. a. increasing the activation energy b. decreasing the activation energy c. decreasing the rate constant d. increasing the enthalpy of the reaction

B

28. When a liquid is heated to its boiling point, it begins changing to the gaseous phase because: (a) hot molecules rise above the cooler ones. (b) the kinetic energy increases and overcomes the forces that hold the molecules close together. (c) the kinetic energy increases, which increases the forces of attraction between the molecules. (d) as the temperature increases, kinetic energy decreases, allowing intermolecular forces to weaken. (e) none of the above.

B

3. The force due to hydrogen bonding must be overcome in the boiling of _____. A) CH3OCH3 B) NH3 C) SbH3 D) C2H5OC2H5

B

4. The vapor pressure of Hg at its normal boiling point is _____ mmHg. A) 100 B) 760 C) 460 D) 1

B

9. In the question: Which compound should have the lowest volatility at room temperature? Compound Molar heat of vaporization A 50 KJ/mol B 100 KJ/mol C 300 KJ/mol D 150 KJ/mol The reason for your choice is: a) The greater the heat of vaporization the more easily the molecules of liquid will go into the gas phase because more energy will be released by the system to the environment in that process. b) The greater the heat of vaporization the stronger the forces of attraction between molecules and consequently, the lower the volatility. Volatility is the ease with which a sample of liquid will evaporate from an open container, like a beaker. c) The greater the heat of vaporization the greater the volatility, that is, the faster a sample of the liquid in an open container will completely evaporate from it. d) The heat of vaporization can be visualized as the work required to move the molecules of the compound from the liquid into the gas phase. Therefore the higher the heat of vaporization, the higher the volatility at a given temperature and pressure. e) Volatility is proportional to the heat of evaporation because both go hand in hand with the strength of the intermolecular forces of attraction.

B

Calculate the amount of heat required to melt 1kg of ice at its melting point given that Hfus = 6.00 kJ/mol A. 61.1 J B. 333.5 kJ C. 5.66 kJ D. 6.19 kJ E. 6,190 kJ

B

Ethanol undergoes combustion in oxygen to produce carbon dioxide gas and liquid water. The standard heat of combustion of ethanol, C2H5OH(l), is -1366.8 kJ/mol. Given that Hf[CO2(g)] = -393.5 kJ/mol and Hf[H2O(l)] = -285.8 kJ/mol, what is the standard enthalpy of formation of ethanol? A. -687.6 kJ/mol B. -277.6 kJ/mol C. 687.6 kJ/mol D. 1,367 kJ/mol E. 3,010 kJ/mol

B

4. What statement/s about hydrogen bond is/are correct: a) Hydrogen bond occurs always when F, N and O interact with each other b) For hydrogen bond to occur, hydrogen has to be bonded to some very electronegative elements. c) The presence of very electronegative elements in the molecule and of hydrogen is enough for hydrogen bonds to occur. d) Hydrogen bond can explain the spatial configuration of ice and why it is less dense than liquid water at 4 degrees C e) Of these compounds only HF forms hydrogen bonds: CH3 O CH3, CHF3, HF, (CH3)3-N

B,D,E

11. What volume of ethanol (density = 0.7893 g/cm3) should be added to 450. mL of water in order to have a solution that freezes at -15.0C? [For water, Kf = 1.86 C/m.] A. 371 mL B. 470 mL C. 212 mL D. 132 mL E. 167 mL

C

11. Which of the following liquids will evaporate faster if we reduce the pressure at constant temperature: A. H2O B. HBr C. Br2 D. Hg

C

13. Kp will be less than Kp if _____. A) H = negative B) n = positive C) n = negative D) n = 0

C

14. What is the heat of fusion of chromium in kJ/mol if 10.0 grams of solid chromium absorb 2.82 x 103 J of heat in melting at 2173 K, its melting point? (a) 1.34 kJ/mol (b) 6.86 kJ/mol (c) 14.7 kJ/mol

C

15. Calculate the amount of heat required to convert 10.0 grams of ice at -200C to steam at 1200C. (Sp. heat of H2O(s) = 2.09 J/g0C, Sp. heat of H2O(l) = 4.18 J/g0C, of H2O(g) = 2.03 J/g0C; heat of fusion of H2O(s) = 333 J/g, heat of evap, of H2O(l) = 2260 J/g) (a) 18.6 kJ (b) 26.3 kJ (c) 30.9 kJ (d) 41.2 kJ (e) 46.4 kJ

C

17. Dissolving a solute such as KOH in a solvent such as water results in A. an increase in the melting point of the liquid. B. a decrease in the boiling point of the liquid. C. a decrease in the vapor pressure of the liquid. D. no change in the boiling point of the liquid.

C

19. In which of the following would London forces be the only significant factors in determining boiling point? I.Ar II. Li2SO4 III. SiF4 IV. Br2 V. NH3 (a) I, II, and III (b) II, IV, and V (c) I, III, and IV (d) I and IV (e) II and V

C

20. The correct order of decreasing freezing points of the solution is (i) 0.5 M H2SO4 (ii) 0.5 M glucose (iii) 0.5 M NaCl and (iv) 0.5 M CaCl2 is _____. a. iv > i > ii > iii b. iii > ii > i < iv c. ii > iii > i > iv d. i > iv > iii > iv

C

21. Which of the following will have the highest osmotic pressure? a. 0.1 M urea b. 0.1 M glucose c. 0.1 M sodium chloride d. 0.1 M sucrose

C

26. On a relative basis, the weaker the intermolecular forces in a substance are, (a) the larger is its heat of vaporization. (b) the more it deviates from the ideal gas law. (c) the greater is its vapor pressure at a particular temperature. (d) the larger is its molar heat capacity as a liquid. (e) the higher is its melting point.

C

5. What is/are typical differences between molecular and ionic compounds? i. Molecular compounds conduct electricity in the melt, while ionic compounds do not. ii. Ionic compounds conduct electricity in the melt, but molecular compounds do not. iii. Most molecular compounds display stronger intermolecular forces of attraction than ionic compounds iv. If an ionic compound is water soluble, the solution will conduct electricity. v. If a molecular compound is water soluble, the solution will conduct electricity A. (i, iii) B. (ii, iii) C. (ii, iv) D. (I, iii, iv) E. (iii, iv)

C

7. What is the percent CdSO4 by mass in a 1.0 molal aqueous CdSO4 solution? A. 0.001 % B. 0.10 % C. 17.2 % D. 20.8 % E. 24.4 %

C

8. Which compound should have the lowest volatility at room temperature? Compound Molar heat of vaporization A 50 KJ/mol B 100 KJ/mol C 300 KJ/mol D 150 KJ/mol

C

Butane (C4H10) undergoes combustion in excess oxygen to generate gaseous carbon dioxide and water. Given Hf[C4H10(g)] = -124.7 kJ/mol, Hf[CO2(g)] = -393.5 kJ/mol, Hf[H2O(g)] = -241.8 kJ/mol, how much energy is released (kJ) when 8.30 g of butane is burned? A. 22,100 kJ B. 2,658.3 kJ C. 379 kJ D. 759 kJ E. 2,910 kJ

C

Given that CaO(s) + H2O(l) Ca(OH)2(s), Hrxn = -64.8 kJ/mol, how many grams of CaO must react in order to liberate 525 kJ of heat? A. 6.92 g B. 56.1 g C. 455 g D. 606 g E. 3.40 104 g

C

The reaction that represents the standard enthalpy of formation for sucrose (C12H22O11) is: A. C12H22O11(s) + 12 O2 12 CO2(g) + 11 H2O(g) B. 12 C(diamond) + 11 H2(g) + 11/2 O2(g) C12H22O11(s) C. 12 C(graphite) + 11 H2(g) + 11/2 O2(g) C12H22O11(s) D. 24 C(diamond) + 22 H2(g) + 11 O2(g) 2 C12H22O11(s) E. C12H22O11(s) 12 C(graphite) + 11 H2(g) + 11/2 O2(g)

C

Which of the following processes is exothermic, given the following: N2(g) + 2 O2(g) N2O4(l) H = 9.67 kJ/mol N2(g) + 2 O2(g) 2 NO2(g) H = 67.70 kJ/mol A. 2 N2(g) + 4 O2(g) 2 N2O4(l) B. ½ N2(g) + O2(g) ½ N2O4(l) C. N2O4(l) N2(g) + 2 O2(g) D. 2 N2(g) + 4 O2(g) 2 NO2(g) + N2O4(l) E. 2 N2(g) + 4 O2(g) 4 NO2(g)

C

7. What properties indicate the presence of strong intermolecular forces of attraction? (more than one may do so) A. High volatility (liquid evaporates easily from a beaker) B. High vapor pressure C. High boiling point D. High critical temperature E. High heat of fusion

C,D,E

14. In the course of research, a chemist isolates a new compound with an empirical formula C3H3O2. 2.51 g of the compound when dissolved in 100. g of water produces a solution with a freezing point of -0.325C. What is the molecular formula of the compound? (For water, Kf = 1.86C/m.)

C6H6O4

1. Potential energy is A. the energy stored within the structural units of chemical substances. B. the energy associated with the random motion of atoms and molecules. C. solar energy, i.e. energy that comes from the sun. D. energy available by virtue of an object's position.

D

18. Which of the following is dependent on temperature? A) mole fraction B) percent by mass C) molality D) molarity

D

20. Which response includes all of the following substances that can exhibit hydrogen bonding, and no others? I. H2 II. CH4 III. NH3 IV. SiH4 V. HF (a) II and V (b) I, II, and III (c) III, IV, and V (d) III and V (e) I, III, and IV

D

23. All of the following are gases at room temperature and atmospheric pressure. Which one will liquefy most easily when pressurized at a certain temperature? (a) H2 (b) Ar (c) SiH4 (d) NH3 (e) F2

D

25. Nitric oxide in the reaction: 2NO + O2 2NO2 reacts at the rate of 0.066 Ms-1. The rate at which O2 reacts is _____ Ms-1. a. 0.132 b. 0.066 c. 0.264 d. 0.033

D

28. The rate of a reaction depends on _____. a. concentration of the reactants b. temperature of the reactants c. catalyst used in the reaction d. all the above

D

3. London or dispersion forces are due to: a) Electronegativity differences between atoms in a molecule lead to a spatial separation of positive and negative charged centers. Positive and negatively charged centers belonging to different molecules attract each other, leading to a net attractive force between the molecules. This is called the polarizability. b) The presence of hydrogen atoms attached to strongly electronegative atoms like F, O, and N in the molecule leads to the formation of particularly strong intermolecular forces of attraction between molecules. c) Atoms of low electronegativity cede electrons to atoms of greater electronegativity. The resulting charged species attract each other electrostatically leading to dispersion or London forces of attraction in the liquid. d) Even in non-polar molecules the electrons that surround the nuclei of the atoms are in a dynamic state of flux. One could speak of an electronic cloud that surrounds the core of the molecule made of the nuclei of the atoms and less mobile core electrons. At any time, one could expect that cloud to be leaning to one side of the molecule, and generate a temporary asymmetry of the positive and negative charges. Before the imbalance disappears by a movement of the cloud in the opposite direction, other molecules in the vicinity respond by realigning their own electronic clouds. This leads to a temporary attraction between basically non polar molecules. The strength of the attraction depends on the number of electrons available to the cloud and also on how loose those electrons are held by the molecule. That is their polarizability.

D

5. Which of the following compounds should be soluble in CCl4? A. NaCl B. H2O C. NaOH D. C8H18 E. none of these

D

8. In how many grams of water should 25.31 g of potassium nitrate (KNO3) be dissolved to prepare a 0.1982 m solution? A. 250.0 g B. 792 g C. 1,000. g D. 1,263 g E. 7,917 g

D

9. Calculate the molality of a 20.0% by mass ammonium sulfate (NH4)2SO4 solution. The density of the solution is 1.117 g/mL. A. 0.15 m B. 1.51 m C. 1.70 m D. 1.89 m E. 2.10 m

D

Aluminum metal has a specific heat of 0.900 J/g·C. Calculate the amount of heat required to raise the temperature of 10.5 moles of Al from 30.5 C to 225C. A. 1.84 kJ B. 2.41 kJ C. 65.1 kJ D. 49.6 kJ E. 57.3 kJ

D

Calculate the amount of work done, in joules, when 2.5 mole of H2O vaporizes at 1.0 atm and 25C. Assume the volume of liquid H2O is negligible compared to that of vapor. (1 L·atm = 101.3 J) A. 61.1 J B. 518 J C. 5.66 kJ D. 6.19 kJ E. 6,190 kJ

D

The reaction that represents the standard enthalpy of formation for benzene (C6H6) is: A. 6 C(diamond) + 3 H2(g) C6H6(l) B. 6 C(graphite) + 6 H(g) C6H6(l) C. C6H6(l) + 15/2 O2(g) 6 CO2(g) + 3 H2O(g) D. 6 C(graphite) + 3 H2(g) C6H6(l) E. C6H6(l) 6 C(graphite) + 3 H2(g)

D

10. Choose the response that lists the member of each of the following pairs that has the lowest melting point: (I) NH3 and LiBr (II) H2O or HBr (III) Kr or Ne A: NH3, H2O and Kr B:NH3, H2O and Ne C.LiBr, H2O and Ne D: LiBr, H2O and Kr E: NH3, HBr, Ne

E

12. When 12.1 g of the sugar sucrose (a nonelectrolyte) are dissolved in exactly 800 g of water, the solution has a freezing point of -0.082C. What is the molar mass of sucrose? Kf of water is 1.86C/m. A. 426 g B. 99.2 g C. 178 g D. 266 g E. 343 g

E

12. Which of the following statements is true regarding water? A. Ice is more dense than water B. The only intermolecular force of attraction between water molecules is hydrogen bonds. C. The only intermolecular force of attraction between water molecules is permanent dipole to permanent dipole D. Water molecules do not display London forces of attraction. E. The most important intermolecular force of attraction between water molecules is hydrogen bond formation

E

16. Which of these molecular properties affects the magnitude of the London forces of attraction? A. Polarizability B. Number of total electrons in the molecule C. Molar mass D. Distance of the electrons from the nucleus (how loosely they are held) E. All of the above

E

2. Among noble gases the strongest intermolecular force of attraction is: a) Double Bonds b) Hydrogen Bonds c) Ionic forces of attraction d) Ion Dipole interaction e) Dispersion forces

E

22. Which response has the following substances arranged in order of increasing boiling point? Ar, NaClO3, H2O, H2Se (a) NaClO3<H2O<H2Se<Ar (b) NaClO3<H2Se<H2O<Ar (c) Ar<NaClO3<H2Se<H20 (d) Ar<H2O<H2Se<NaClO3 (e) Ar<H2Se<H2O<NaClO3

E

6. Which of the following substances should have the lowest melting point? A. H2 B:.HBr c: LiBr d: CH3OH e: He

E

Which of the following has a Hf= 0 kJ/mol? A. NO(g) B. CS2(l) C. Fe2+(aq) D. H2O(l) E. N2(g)

E