T2S1422.98F
                         CHEM 1212   SAMPLE TEST #2 (100 pts)    10/xx/9x Name ____________________

GPC (Dunwoody,  Dr. Kim)                                 Calculator & Model # ___________________


Use a Scantron for Multiple Choices.

R=8.3145J/(K.mol); 1cal=4.184J; 1mi=1.609km; 1yd=0.9144m; 1gal=3.785L; 1lb=453.6g;
1atm=101,325Pa; d(water)=0.997g/mL; d(Hg)=13.6g/mL; NA=6.022x1023/mol; c=2.9979x108m/s;
1amu = 1.66x10-27kg; e=1.602x10-19C; G=6.6726x10-11Nm2/kg2; k=8.9876x109J.m/C2.


1. When red blood cells are placed in pure water, they (a) swell, (b) shrink, because the rate of movement of solvent(H2O) molecules across the cell membrane from outside into the cell is
(c) larger, (d) smaller than that from inside the cell to outside. A(a,c), B(a,d), C(b,c), D(b,d).

2. Size of colloidal particles is in a range of (a) 1mm-1µm, (b) 1 µm-1nm;
Colloidal solution shows (c) Tyndall, (d) Joule-Thomson Effect. A(a,c), B(a,d), C(b,c), D(b,d).

3. Which one is related to a coagulation of colloidal particles? A(Absorption of H2O by roots),
B(Food preservation with salts), C(Desalination of brackish water), D(Curdling of milk).

4. Which ionic substance is most effective in coagulating clay particles with negative surface
 charges in a colloidal muddy water?  (A)KCl, (B) CaCl2, (C)Al2(SO4)3, (D)Na3PO4.

5. The formula of a common soap, sodium stearate, is a(C7H15COONa), b(C17H35COONa).
In a cleaning action, the (c) hydrophobic tail, (d) hydrophillic head of soap molecules binds to oily dirts to take it off from fabrics.        A(a,c), B(a,d), C(b,c), D(b,d).

6. A(Hydrophobic tail), B(Hydrophillic head) of a soap molecule(or ion) will bind to water molecules.

7. Soap lowers surface tension of water by (a) strengthening, (b) disrupting, hydrogen-bonds among H2O with their (c) polar heads, (d) hydrocarbon tails. A(a,c), B(a,d), C(b,c), D(b,d).

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8. Reaction rates depends on (A)Concentration of reactants, (B)Concentration of catalyst, (C)Temperature, (D)Surface areas of reactant/catalyst, (E)All of these.

9. Rate constant increases with (A) collision frequency, (B) fraction of collisions having energy greater than activation energy(Ea), (C) fraction of collisions with proper orientation, (D) all of these.

10. A catalyst will (a) increase, (b) decrease, an activation energy of a reaction
to make the reaction occur (c) slowly, (d) faster. A(a,c), B(a,d), C(b,c), D(b,d).

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    Given the reaction, 2N2O5     ->    4NO + O2, with an initial N2O5 concentration of 0.0165M.

11. Calculate an average reaction rate during the following time interval. [N2O5] are 0.0124M at t=600s & 0.0093M at t=1,200s.     A(2x105s/M), B(2x10-5M/s), C(5x10-6s/M), D(5x10-6M/s), E(-).

12. This decomposition reaction is a first-order reaction with a rate constant k=4.8x10-4s-1 at 45oC.
The half-life(t1/2) must be     A(1.5), B(3), C(6), D(12), E(24) min.

13. Predict a concentration of N2O5 left after 1.5 hour.
        A(0.011), B(0.010), C(0.0010), D(0.0011), E(0.0012)M.

14. The time at which the concentration of N2O5 equals to that of O2 is ca.
        A(40), B(50), C(60), D(70), E(80) min.

15. How long does it  take for the concentration of N2O5 to decrease to 10% of the original concentration?
        A(75), B(80), C(85), D(90), E(95) min.

                                *             *             *             *             *

16. The half-life (t1/2) of first-order reaction is (A) directly, (B) inversely, (C) exponentially proportional to, (D) independent of, the reactant concentration.

17. A first-order reaction will yield a straight line in a plot of A([A] vs. t), B([A]-1 vs. t-1),
C([A]-1 vs. t), D(ln[A] vs. t), E(ln[A] vs. t-1) where [A] is a reactant concentration at time t.

18. In the two-step mechanism of a reaction:

            NO2(A) + NO2     ->    NO3(B) + NO(C)

            NO3 + CO(D)        ->    NO2 + CO2(E)                     Which one is an intermediate?

19. Decomposition of an ozone excited by a UV radiation from the Sun:    O3*    ->    O2    +    O
in the stratosphere is     (A)Uni-, (B)Bi-, (C)Ter-molecular reaction.

20. The automobile catalytic converter contains (A) Pt, (B)Fe, (C) NO, (D)Zn, catalyst.

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21. Decomposition of NO2:     NO2(g)    ->    2NO(g)+O2(g) follows a second-order rate law, (k=0.775s/M). The reaction started with 2.00M NO2 . What is the half-life, t1/2, of this reaction?      A(0.918), B(0.918), C(918), D(0.645), E(645)s.

22. Concentration of the reactant leftn after 1min above is ca. A(1), B(0.2), C(0.02), D(0.002) M.

23. According to the collision theory, reaction rate approximately doubles for every temperature increases of 10oC. It takes about 8 min to cook an average  carrot in a normal boiling water of 100 oC.  How long does it take if it is done in a pressure cooker is 120oC ?
(A) 30 sec, (B) 1min, (C) 2min, (D) 6min,  (E) 8 min.                             *             *             *             *             *

    Chlorine dioxide, ClO2, is a reddish-yellow gas that is soluble in water, in basic solution it gives ClO3- and ClO2- ions:

            2ClO2 (aq) + 2OH-(aq) ->  ClO3- (aq) + ClO2- (aq) + H2O

To obtain the rate law for this reaction, the following three experiments were run and, for each, the initial rate of reaction of ClO2 was determined.
 
 
  Initial Concentration(mol/L)
ClO2		 Initial Concentration(mol/L)
OH-		 Initial Rate
(mol/((L s))
Exp. 1 0.060 0.030 0.0248
Exp. 2 0.020 0.030 0.00276
Exp. 3 0.020 0.090 0.00828
Exp. 4 0.040 0.060       ?

24. What is the reaction order with respect to ClO2 ?
A(Zeroth-order), B(First-order), C(Second-order), D(Third-order), E(Fourth-order)

25. What is the reaction order with respect to OH- ?
A(Zeroth-order), B(First-order), C(Second-order), D(Third-order), E(Fourth-order)

26. What is the overall  reaction order ?
A(Zeroth-order), B(First-order), C(Second-order), D(Third-order), E(Fourth-order)

27. What is the rate law equation for the reaction ?   Rate =
A( k[ClO2][OH-] ),  B( k[ClO2]2[OH-] ), C( k[ClO2][OH-]2), D( k[ClO2]2[OH-]2 ) , E( k[ClO2] )

28. Find the value of the rate constant, k.
A(4.6), B(153), C(230), D(3890), E(7670) M-2 s-1.

29. Predict an initial rate for the Experiment #4.
A(0.00133), B(0.00414), C(0.00828), D(0.0221), E(0.0331),  F(0.552)  mol/(L s).


Answer Any One out of Four. Circle the number chosen. Show all of your work.
 

I. Write down the chemical formula for a typical soap molecule (Sodium Stearate). Explain the cleansing action of soap using such key terms as polar, non-polar, hydrophilic, hydrophobic, and micelle.

II. Compare a first-order reaction with a second-order one. Explain with rate equations, graphs and examples. How can you distinguish experimentally a first-order from a second-order reaction?

III. Explain the three factors that determine the rate constant(k): k=pfZ.

IV. Rate constants(k) for above reaction, H2(g)+I2(g) ->    2HI(g), is 2.7x10-4L/(mol.s) at 600K and 3.5x10-3L/(mol.s) at 650K. (1) Find the activation energy(Ea). (2) Predict a k value at 670K.


The KEY to the Multiple Choice Questions  (10/11/98)