Answers to Section 1 Midterm Test 1 Card 002

Answers are marked by a star "*".

A problem usually have many ways to solve, and NOT all reasoning processes to arrive at the answers can be given. Thus, please work on the problems that you have not solve correctly. Skills you gained in doing so will be useful during the final exam.

I want to emphasize again what I have preached during the lecture that practice is the best way to learn. For this reason, only the answers are marked. No solutions are given.

For some methods, you may see solutions to Midterm Tests in other sections. Problems for all sections are similar in concepts tested.

Solutions to Section 2 Midterm Test-1

Solutions to Section 3 Midterm Test-1

  1. Hydrogen bonding is the dominating intermolecular interaction for which one of the following solids?

    1. methane, CH4
    2. Hydrogen, H2
    3. Hydrogen iodide, HI
    4. *Ammonia, NH3
    5. Sodium hydride NaH

  2. Please consider the dominant intermolecular interaction for your answer to this question.
    Which one of the following has the highest melting point?

    1. H2S
    2. CH3CH2CH2SH
    3. *Na2SO4
    4. Xe
    5. O3

  3. Which one of the following describes accurately the phase or phases present in a system consisting of pure water at 1.0 atm and 250 K?

    1. *solid
    2. liquid
    3. gas
    4. liquid and gas
    5. solid and gas

  4. The heat of vapourization of acetone is 25.5 kJ mol-1, and its normal boiling point is 56.2o C. What is the temperature when the vapour pressure is 700 mmHg?

    1. 45o C
    2. 41o C
    3. 59o C
    4. *53o C
    5. 48o C

  5. The alkali metal rubidium (Rb, atomic mass 85.46, atomic number 37) has a body centred cubic structure. The edge of the cubic unit cell is 558.5 pm (1 pm = 10-12 m). What is its density?

    1. * 1.63 g cm-3
    2. 0.815 g cm-3
    3. 8.150 g cm-3
    4.  3.26 g cm-3
    5.  2.73 g cm-3

  6. Gold (Au) crystallizes in a face-centred cubic (fcc) structure. The edge length of the fcc unit cell is 408 pm. What is the radius of a gold atom according to the sphere-packing model?

    1. 204 pm
    2. 288 pm
    3. 177 pm
    4. 408 pm
    5. *144 pm

  7. In the crystal structure of Li2S, the sulfide ions, S2-, form a face-centred cubic lattice with the Li+ occupying the tetrahedral sites (or tetrahedral holes).

    How many Li+ ions and how many S2- ions are present within a face-centred cubic unit cell?

    1. 28 Li+ and 14 S2- ions
    2. *8 Li+ and 4 S2- ions
    3. 8 Li+ and 14 S2- ions
    4. 4 Li+ and 2 S2- ions
    5. 2 Li+ and 1 S2- ions

  8. From the following data:

    Chemical Reaction Enthalpy
    /kJ mol-1
    Ca (s) ® Ca (g) 178
    Ca (g) ® Ca+ (g) + e- 590
    Ca+ (g) ® Ca2+ (g) + e- 1145
    Cl2 (g) ® 2 Cl (g) 244
    Cl (g) + e- ® Cl- (g) - 349
    CaCl2 (s) ® Ca(s) + Cl2 (g) 796

    What is the enthalpy change for the reaction below in kJ?

    Ca2+ (g) + 2 Cl- (g) ® CaCl2 (s)

    1. + 2604
    2. - 2604
    3. + 2255
    4. - 2455
    5. *- 2255

  9. A series of experiments were carried out to determine the rate law of the reaction:

    A + 2 B + C ® products .

    The initial rate for the consumption of A is measured as soon as the reactants are mixed.

    Expt 1 2 3 4
    [A]o   0.100     0.150     0.150     0.100  
    [B]o   0.100   0.100   0.250   0.100
    [C]o   0.100   0.100   0.100   0.200
    initial
    rate
      0.120   0.220   0.348   0.480

    What is the order with respect to the reactant B?

    1. 1
    2. 2
    3. *0.5
    4. 1.5
    5. 2.5

  10. In order to determine the rate constant k, a series of experiments have been carried out to measure the initial rate. The data are given in the Table below.

    A + B ® products .

    The initial rate is measured as soon as the reactants are mixed.

    Expt 1 2 3
    [A]o   0.100   0.200   0.200
    [B]o   0.100   0.100   0.300
    initial rate / mol L-1 s-1   0.00231    0.00924    0.02772


    What is the rate constant k?

    1. 0.00231 mol2 L-2 s-1
    2. 0.0231 mol2 L-2 s-1
    3. 0.231 mol2 L-2 s-1
    4. *2.31 mol2 L-2 s-1
    5. 23.1 mol2 L-2 s-1

  11. A compound X decomposes according to first-order kinetics and 25% of a particular sample decomposes in 50 seconds. What is the half-life t1/2?

    1. 130 s
    2. 110 s
    3. *120 s
    4. 100 s
    5. 90 s

  12. At t = 0, the compound Y has a concentration of 5.00 mol L-1. The compound Y reacts according to second order kinetics. A measurement at t = 10 min gives [Y] = 4.00 mol L-1.
    What is [Y] at t = 30 minutes?

    1. 3.37 mol L-1
    2. *2.86 mol L-1
    3. 2.62 mol L-1
    4. 2.23 mol L-1
    5. 3.00 mol L-1

  13. The decomposition of a compound Z is second-order with respect to Z. Which one of the following is correct? In the following, t is the parameter for time.

    1. A plot of ln [Z] versus t yields a straight line with slope -k.
    2. *A plot of [Z]-1 versus t yields a straight line with slope k.
    3. A plot of ln [Z] versus t-1 yields a straight line with slope -k.
    4. A plot of [Z]-1 versus t yields a straight line with slope -k.
    5. A plot of [Z]-1 versus t-1 yields a straight line with slope k.