Chemical Kinetics
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4.22 Calculate the half-life of a first order reaction from their rate constants given below: (i) 200 s–1 (ii) 2 min–1 (iii) 4 years–1
4.22 Calculate the half-life of a first order reaction from their rate constants given below: (i) 200 s–1 (ii) 2 min–1 (iii) 4 years–1
4.22 Half life of first order reaction is, t1/2 = ln2/K where t1/2 is half life of first order reaction, K is rate constant of First order reaction.
(i) t1/2 = ln2/200 s-1
⇒t1/2 = 0.693/200 s-1 (? ln2 = 0.693)
⇒t1/2 = 0.003465 sec.
(ii) t1/2 = ln2/2 min-1
⇒t1/2 = 0.693/2 min-1 (? ln2 = 0.693)
⇒t1/2 = 0.
Upvote 
4.21 The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:
Experiment
[A]/mol L-1
[B]/mol L-1
Initial rate/mol L-1 min-1
I
0.1
0.1
2.0 × 10-2
II
-
0.2
4.0 × 10-2
III
0.4
0.4
-
IV
-
0.2
2.0 × 10-2
4.21 The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:
|
Experiment |
[A]/mol L-1 |
[B]/mol L-1 |
Initial rate/mol L-1 min-1 |
|
I |
0.1 |
0.1 |
2.0 × 10-2 |
|
II |
- |
0.2 |
4.0 × 10-2 |
|
III |
0.4 |
0.4 |
- |
|
IV |
- |
0.2 |
2.0 × 10-2 |
4.21 As reaction is first order with respect to A and zero Order with respect to B. Then changing the concentration of B won't affect the rate of reaction and increasing concentration of A 'n' times will increase the rate by 'n' times. By this logic lets fill the table- In first blank space con
Upvote 4.20 The following results have been obtained during the kinetic studies of the reaction: 2A + B → C + D
Determine the rate law and the rate constant for the reaction.
4.20 The following results have been obtained during the kinetic studies of the reaction: 2A + B → C + D
Determine the rate law and the rate constant for the reaction.
4.20 By comparing Experiment I and IV if we increase the concentration of A by 4 times then Rate also increased by 4 times. That means order with respect to A is 1.
By comparing Experiment II and III if we double the concentration of B Rate increases by 4 times that means order with respect to B
Upvote 4.19 In a reaction between A and B, the initial rate of reaction(r0)was measured for different initial concentrations of A and B are given below: What is the order of the reaction with respect to A and B?
A/mol L-1
0.20
0.20
0.40
B/mol L-1
0.30
0.10
0.05
r0/mol L-1s-1
5.07 × 10-5
5.07 × 10-5
1.43 × 10-4
4.19 In a reaction between A and B, the initial rate of reaction(r0)was measured for different initial concentrations of A and B are given below: What is the order of the reaction with respect to A and B?
|
A/mol L-1 |
0.20 |
0.20 |
0.40 |
|
B/mol L-1 |
0.30 |
0.10 |
0.05 |
|
r0/mol L-1s-1 |
5.07 × 10-5 |
5.07 × 10-5 |
1.43 × 10-4 |
4.19 When concentration of B is changed then rate of reaction doesn't change that means order with respect to B is 0. But when the concentration of A is doubled rate increased by 2.82 times i.e.21.5 = 2.82.Hence order with respect to A is 1.5.
Order with respect to A and B is 1.5 and 0, respecti
Upvote 4.18 A reaction is first order in A and second order in B.
(i) Write the differential rate equation.
(ii) How is the rate affected on increasing the concentration of B three times?
(iii) How is the rate affected when the concentrations of both A and B are doubled?
4.18 A reaction is first order in A and second order in B.
(i) Write the differential rate equation.
(ii) How is the rate affected on increasing the concentration of B three times?
(iii) How is the rate affected when the concentrations of both A and B are doubled?
4.18 (i) Order is power raised to reactant in rate law, hence,
Rate = k [A] [B]2
(ii) When the concentration of B is increased three times then the rate is affected by the square of The rate is increased by 9 Times.
(iii) When the concentration of reactant both A and B is doubled then the rate
Upvote 4.17 In a pseudo first order hydrolysis of ester in water, the following results were obtained, Calculate the average rate of reaction between the time intervals 30 to 60 seconds.
t/s
0
30
60
90
[Ester]/mol L-1
0.55
0.31
0.17
0.085
4.17 In a pseudo first order hydrolysis of ester in water, the following results were obtained, Calculate the average rate of reaction between the time intervals 30 to 60 seconds.
|
t/s |
0 |
30 |
60 |
90 |
|
[Ester]/mol L-1 |
0.55 |
0.31 |
0.17 |
0.085 |
4.17 (i) Average rate of reaction over interval is [change in concentration]/ [time taken] e.
[0.31 - 0.17] / [60-30] = 0.00467 mol L-1 sec-1
(ii) the pseudo first-order rate constant can be calculated by K = (2.303/t) log (Ci/Ct)
where K is Rate constant,
t is time taken,
Ci is initial concent
Upvote 4.16 What is the effect of temperature on the rate constant of a reaction? How can this effect of temperature on rate constant be represented quantitatively?
4.16 What is the effect of temperature on the rate constant of a reaction? How can this effect of temperature on rate constant be represented quantitatively?
4.16 Increase in temperature increases the rate constant of a reaction. as we know increase in temperature increases the rate of reaction to satisfy the equation Rate = k [concentration]n where n can be any real number. k have to increase as concentration is almost not changing over small tempe
Upvote 4.15 A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is (i) doubled (ii) reduced to half?
4.15 A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is (i) doubled (ii) reduced to half?
4.15 Let suppose reaction
A? B; having rate law, Rate = K [A]2
(i) If the concentration of A is doubled then the rate will affect by the square of concentration i.e. rate will become 22 = 4 times.
(ii) If the concentration of A is halved, then the rate will affect the square of the concent
Upvote 4.14 Mention the factors that affect the rate of a chemical reaction.
4.14 Mention the factors that affect the rate of a chemical reaction.
4.14 Factors affecting rate of reaction-
1) Temperature (increasing temperature increases rate of reaction)
2) Concentration or pressure of reactants. (Increasing concentration or pressure increases rate of reaction)
3) Presence or absence of a (Adding catalyst mostly increases the rate of reactio
Upvote 4.13 The decomposition of dimethyl ether leads to the formation of CH4 , H2 and CO and the reaction rate is given by Rate = k [CH3OCH3 ] 3/2 The rate of reaction is followed by increase in pressure in a closed vessel, so the rate can also be expressed in terms of the partial pressure of dimethyl ether, i.e., Rate= k(PCH3OCH3)3/2 If the pressure is measured in bar and time in minutes, then what are the units of rate and rate constants?
4.13 The decomposition of dimethyl ether leads to the formation of CH4 , H2 and CO and the reaction rate is given by Rate = k [CH3OCH3 ] 3/2 The rate of reaction is followed by increase in pressure in a closed vessel, so the rate can also be expressed in terms of the partial pressure of dimethyl ether, i.e., Rate= k(PCH3OCH3)3/2 If the pressure is measured in bar and time in minutes, then what are the units of rate and rate constants?
4.13 Rate of given chemical reaction will be represented as
-d [pCH3OCH3] / dt
Hence units of rate is bar min-1
To find units of K, K = rate/ [pCH3OCH3]3/2
The unit of k = bar -1/2min-1.
Units of Rate- bar min-1. and Units of Rate constant K : bar -1/2min -1
Upvote