School of Technology Technology University of the Philippines Visayas ChE125 Chemical Reaction Engineering Pre-Exam Activity Kindly Kind ly write the appropriate letter letter for f or the best answer answer of o f your choice cho ice beside the number. In case your answer is not found in the choices, write letter E. 1.
The equilibrium c onstant in a reversible reversible chemical rea reaction ction at a given temperat temperature ure A. depends on the initial conc of the reactants B.
depends on the conc of one of the products at equilibrium
D.
is not a characteristic of the reaction
2.
If the volume of a rea reaction ction vesse vessell is suddenly reduced to one half its original volume vo lume the rate will increa inc rease se b y a factor of B. 4.00 C. 8.00 D. 16.00
3.
A reaction is known to be first order in A. A straight line will be obtained by plotting
4.
B. Ca vs time C. Log Ca vs 1/time If the reaction reaction 2A ---> B+C B+C is second order, whic h of the following plots will give a straight line? A.
5.
Ca^2 vs time
C. D.
D.
1/Ca vs time
log Ca vs v s time Ca vs time
For the reaction A+B ---> 2C, when Ca is doubled the rate doubles, when Cb is doubled the rate increases fourfold. The rate law is A.
-ra = k Ca^2 Cb^4
C.
-ra = k Ca
6.
D. -ra = k Cb^2 A first order reaction reaction has a specific rate c onstant of 3e-3 per sec. The half life is
7.
A. 0.0021 s B. 100 s D. 768 s A certain reaction is 1st order in A. In 30 min, the conc entration entration of A decreases decreases from 0.55 to 0.15 mol/L. The time it will t ake for A to decrease decrease from 0.35 to 0.15 mol/L mol/L is A. 45.1 min
8.
C.
19.1 min
D.
10.4 min
A gas decomposes decomposes at 900 degC according to 2A--->2R+S wi th a rate rate constant of 1000 cc/gmol-s using pure A. The time it will take to react 80 % of A in a batch batc h reactor reactor at 900 degC and 1 atm in min is A.
3.83
B.
7.43
C.
8.33
D.
9.33
(6.42 (6.42 min m in))
9.
E When the 1st order order homogene ho mogeneous ous reaction reaction (gas-phase) A--->2.5R A--->2.5R is i s carried carried out in an isothermal isothermal batch reactor reactor at 2 atm with 20% inerts present, the vo lume increa inc reases ses by b y 60% in 20 min. When th e reaction reaction is carried carried out in a constant con stant volume reactor, the time required required for the pressure pressure to reach reach 8 atm if the initial pressure is 5 atm, atm, 2 atm of whic which h consist of inerts inerts in min i s A. E
43.10
(31.66 min) min)
B.
41.30
C.
37.10
D.
31.80
10. The reaction A+2B--->R is 1st order with respect to each reactant. If equimolar amounts of A and B are introduced into a constant-volume reactor and (1/m) th of A remains after t1, how much will remain after t2=2t1? A. Cao/2m B. Cao/(2m-1) C. Cao/(1-2m)
D.
Cao/2
− 11. The set of data given below is for the parallel reaction: reaction: a---k1-->2R, a---k2 -->S. At t=0, Ca=15 moles/cuft, moles/cuft, Cr = 1 mole/cuft mole/cuft , Cs=1 mole/cuft; At t=1 hr, Cr = 9 moles/cuft, Cs = 3 moles/cuft. The value of K2 per hour is A. 0.17 B. 0.18 C. 0.34
D.
0.62
12. If the the time required to complete a definite definite fraction of reaction reaction varies inversely inversely as the c oncentra onc entration tion of the reactants, reactants, then the order of reaction is A. 1 13. The dimensions of rate constant for reaction A. 1
C.
3
D.
4
3 → are (l/gm (l/ gm mole)/ mole)/min. min. Therefore the reaction order is C.
