c123fe-sample-mc

c123fe-sample-mc - CHEM 123 SAMPLE EXAM QUESTIONS 1. How...

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CHEM 123 SAMPLE EXAM QUESTIONS 2 1. How many spheres lie within one unit cell of a body-centred cubic lattice of identical, hard spheres? A. one B. two C. four D. eight E. nine 2. Aluminum (Al) crystallizes in a face-centred cubic structure. If the radius of the aluminum atom is 140 pm, then what is edge length of the unit cell? A. 200 pm B. 280 pm C. 320 pm D. 400 pm E. 560 pm 3. Which one of the following statements is correct for a closest-packed lattice of identical, hard spheres? A. The coordination number of each sphere in the lattice is eight. B. The number of tetrahedral holes in the lattice is exactly equal to the number of spheres. C. There are more tetrahedral holes than octahedral holes in the lattice. D. More than 80% of the total volume of the lattice is occupied by spheres. E. The unit cell of the lattice is either simple cubic or face-centred cubic. 4. The overall chemical equation for the combustion of carbon monoxide, CO, is 2 CO( g ) + O 2 ( g ) 2 CO 2 ( g ). Which one of the following expressions is correct? A. d [CO]/ dt = d [CO 2 ]/ dt B. Rate = k [CO] 2 [O 2 ] C. Rate = [CO] 2 /([CO] 2 [O 2 ]) D. d [CO 2 ]/ dt = 2 d [O 2 ]/ dt E. d [CO]/ dt + d [O 2 ]/ dt = d [CO 2 ]/ dt
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CHEM 123 SAMPLE EXAM QUESTIONS 3 5. In a certain experiment, the rate law for the reaction, H 2 O 2 products, was determined to be d [H 2 O 2 ]/ dt = k [H 2 O 2 ] with k = 1.06 × 10 3 min 1 . What is the concentration of H 2 O 2 after 100 min, if the initial concentration of H 2 O 2 was 0.200 mol L 1 ? A. 0.0212 mol L 1 B. 0.0940 mol L 1 C. 0.106 mol L 1 D. 0.157 mol L 1 E. 0.180 mol L 1 6. The decomposition of compound A follows a second-order rate law. Which one of the following plots is linear? ( [A] is the concentration and t is time.) A. [A] vs. t B. ln[A] vs. t C. 1/[A] vs. t D. [A] vs. 1/ t E. ln[A] vs. 1/ t 7. The activation energy (E a ) for a certain reaction is 182 kJ/mol and the rate constant (k) is 1.57 × 10 5 mol 1 L s 1 at 973 K. What is the value of the rate constant at 1073 K? A. 1.79 × 10 5 mol 1 L s 1 B. 1.28 × 10 4 mol 1 L s 1 C. 1.93 × 10 5 mol 1 L s 1 D. 1.28 × 10 2 mol 1 L s 1 E. 7.80 × 10 4 mol 1 L s 1 8. The reaction of NO with O 2 to form NO 2 contributes to the formation of urban smog. The following mechanism has been proposed: NO + NO U N 2 O 2 (fast equilibrium) N 2 O 2 + O 2 2 NO 2 (slow) What is the rate law derived from this mechanism? A. Rate = k [NO] 2 [O 2 ] B. Rate = k [NO] 2 C. Rate = k [NO] [O 2 ] 2 D. Rate = k [NO] [O 2 ] E. Rate = k [O 2 ] 2
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CHEM 123 SAMPLE EXAM QUESTIONS 4 9. In a certain reaction (at 298 K), the concentration of compound X, in mol L 1 , varies with time, in seconds, as follows: time: 0 2 4 6 10 20 [X]: 10.0 8.19 6.70 5.49 3.68 1.35 Which one of the following statements is correct? A.
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This note was uploaded on 02/25/2012 for the course CHEM 123 taught by Professor Pols during the Spring '07 term at Waterloo.

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c123fe-sample-mc - CHEM 123 SAMPLE EXAM QUESTIONS 1. How...

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