Multiple Choice QuestionsThe following data is obtained during the first order thermal decomposition of 2A(g)→ B(g) +C(s) at constant volume and temperature.
| S.No | Time | Total pressure in Pascal |
| 1. | At the end of 10 min | 300 |
| 2. | After completion | 200 |
The rate constant in min-1
0.0693
6.93
0.00693
69.3
For a reaction, A + B → products, the rate of the reaction at various concentrations are given below
| Expt no. | [A] | [B] | Rate (mol dm-3 s-1) |
| 1. | 0.2 | 0.2 | 2 |
| 2. | 0.2 | 0.4 | 4 |
| 3. | 0.6 | 0.4 | 36 |
The rate law for the above reaction is
r = k[A][B]2
r = k [A]3[B]
r = k [A]2[B]2
r = k [A]2[B]
The rate of reaction increases with rise in temperature because of
onl increase in number of activated molecules
Increase in energy of activation
decrease in energy of activation , increase in number activated molecules and also the number of effective collisions increase.
only increase in the number of effective collisions
C.
decrease in energy of activation , increase in number activated molecules and also the number of effective collisions increase.
For a collision to be effective, the colloiding molecules must have energy more than a particular value known as threshold energy. At room temperature most of the reactant molecules have energy less than the threshold value. When temperature is increased, the reactant molecules absorb this energy and their energy becomes equal to or greater than threshold value. This extra amount of energy absorbed by the reacting molecules is known as activation energy.
Activation energy = Threshold energy - Average kinetic energy of the reactants.
Evidently, the rate of reaction increases on rise in temperature, because average kinetic energy of the reactants increases and activation energy decreases. Also, on rise in temperature, the number of molecules having kinetic energy greater than threshold value increases. Thus, the increase in the rate of reaction with increase in temperature in mainly due to increase in number of effective collisions.
A first order reaction is 60% complete in 20 minutes. How long will the reaction take to be 84% complete?
68 min
40 min
76 min
54 min
If 50% of the reactant is converted into a product in a first order reaction in 25min, how much of it would react in 100min?
93.75%
87.5%
75%
100%
Temperature coefficient of a reaction is 2. When temperature is increased from 30°C to 90°C, the rate of reaction is increased by
60 times
64 times
150 times
400 times
A (g) P (g) + Q (g) + R (g), follows first order kinetics with a half-life of 69.3 s at 500°C. Starting from the gas 'A' enclosed in a container at 500°C and at a pressure of 0.4 atm, the total pressure of the system after 230 s will be
1.15 atm
1.32 atm
1.22 atm
1.12 atm
In a first order reaction, the concentration of the reactant is reduced to 12.5% in 1hr. When was it half completed?
3hr
20min
30min
15min
The half-life period of a first order reaction is 60 min. What percentage will be left over after 240 min?
6.25%
4.25%
5%
6%
Half-life period of a first order reaction is 10 min. Starting with initial concentration 12 M, the rate after 20 min is
0.0693 M min-1
0.693 × 3M min-1
0.0693 × 3M min-1
0.0493 × 4M min-1
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