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Chemical Kinetics-2020

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ORGANIC CHEMISTRY-I

38 Documents
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Academic year: 2021/2022
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Amity University

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CHEMICAL KINETICS

BOARD QUESTIONS

2010

1.(a) Explain the following term: Rate of a reaction (b) The decomposition of phosphine, PH 3 , proceeds according to the following equation: 4PH 3 (g) P 4 (g) + 6H 2 (g) It is found that the reaction follows the following rate equation: Rate = k[PH 3 ] The half-life of PH 3 is 37 s at 120°C (i) How much time is required for ¾ th of PH 3 to decompose? (ii) What fraction of the original sample of PH 3 remains behind after 1 minute? 2. Explain the following terms: (i) Order of a reaction (ii) Molecularity of a reaction

2011

3.(a) Express clearly what you understand by ‘rate expression’ and ‘rate constant’ of a reaction. (b) Nitrogen pentoxide decomposes according to the equation: 2N 2 O 5 (g) 4NO 2 (g) + O 2 (g) This first order reaction was allowed to proceed at 40°C and the data given below were collected:

[N 2 O 5 ] M Time (min) 0 0. 0 20. 0 40. 0 60. 0 80.

(i) Calculate the rate constant for the reaction. Include units with your answer. (ii) Calculate the initial rate of reaction. (iii) After how many minutes will [N 2 O 5 ] be equal to 0 M. 4.(a) Define: (i) Order of a reaction (ii) Elementary step in a reaction (b) A first order reaction has a rate constant value of 0 min-1. If we begin with 0 M concentration of the reactant, how much of the reactant will remain after 3 hours?

2012

5 the following term: Order of a reaction 6 the reaction: 2A + B C + D Following results were obtained in experiments designed to study the rate of reaction:

Expt. No. Initial conc. (mol L-1) Initial rate of formation [A] [B] [D] (M/min) 1 0 0 1 x 10- 2 0 0 3 x 10- 3 0 0 6 x 10-

(a) Write the rate law for the reaction. (b) Calculate the value of rate constant for the reaction. (c)Which of the following possible reaction mechanisms is consistent with the rate law found in (a). I. A + B C + E (slow) A + B C + E (fast) II. B C + E (slow) A + E F (fast) A + F D (fast)

2013

7 rate constant for a first order reaction is 60 s-1. How much time will it take to reduce the initial concentration of the reactant to 1/10th of its initial value? 8 a chemical reaction R P, the variation in the concentration ln[R] vs time t plot is given as:

ln[R]

t (s) For this reaction: (i) What is the order of the reaction? (ii) What is the slope of the curve? (iii) What is the unit of rate constant ‘k’?

2014

9 half-life of a reaction. Write the expression of half-life for: (i) Zero order reaction (ii) First order reaction

2017

16.(a) A first order reaction is 75% completed in 40 minutes. Calculate its t½. (b) Predict the order of the reaction in the given plots:

t½ t½

[R] 0 [R] 0

Where [R] 0 is the initial concentration of the reactant (Given log 2 = 0,log 4 = 0) (c) The following data were obtained for the reaction: 2NO + O 2 2 NO 2

Experiment [NO]/M [O 2 ]/M Initial rate of formation of NO 2 /M min- 1 0 0 7 x 10- 2 0 0 6 x 10- 3 0 0 2 x 10- 4 0 0 2 x 10-

(a) Find the order of reaction with respect to NO and O 2. (b) Write the rate law and overall order of reaction. (c) Calculate the rate constant (k).

2018

17 the reaction: 2N 2 O 5 (g) 4NO 2 (g) + O 2 (g) The rate of formation of NO 2 (g) is 2 x 10-3 M s-1. Calculate the rate of disappearance of N 2 O 5 (g). 18 first order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction. (Given log 2 = 0, log 4 = 0, R = 8 J K-1 mol-1)

2019

19 the reaction R P, for which the change in concentration of R with time is shown by the following graph:

conc.[R]

Time

(i) Predict the order of reaction. (ii) What does the slope of the curve indicate? 20. A first order reaction takes 30 minutes for 20% decomposition. Calculate t½ (log 2 =0)

2020

21 the overall order of the reaction whose rate law expression was predicted as: Rate = k [NO]3/2 [O 2 ]1/ 22 reaction is first order with respect to reactant A as well as with respect to reactant B. Give the rate law. Also give one point of difference between average rate and instantaneous rate. 23 the overall order of reaction whose rate law is given by: Rate = k [NH 3 ]5/2 [O 2 ]1/ 24. Calculate the overall order of the reaction whose rate law is given by: Rate = k [SO 2 ]1/4 [O 2 ]3/ 25.(a) Visha plotted a graph between concentration of R and time for a reaction R P. On the basis of this graph, answer the following questions:

[R 0 ] Conc. of R

Time

(i) Predict the order of reaction. (ii) What does the slope of the line indicate? (iii) What are the units of rate constant? (b) A first order reaction takes 25 minutes for 25% decomposition. Calculate t½. (Given log 2 = 0, log 3 = 0, log 4 = 0) 26.(a) The rate constant for a first order reaction is 60 s-1. How much time will it take to reduce the initial concentration of the reactant to its 1/16th value. (b) Write two factors that affect the rate of a chemical reaction.

_______________

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Chemical Kinetics-2020

Course: ORGANIC CHEMISTRY-I

38 Documents
Students shared 38 documents in this course

University: Amity University

Was this document helpful?
CHEMICAL KINETICS
BOARD QUESTIONS
2010
1.(a) Explain the following term:
Rate of a reaction
(b) The decomposition of phosphine, PH3, proceeds according to the following equation:
4PH3(g) P4(g) + 6H2(g)
It is found that the reaction follows the following rate equation:
Rate = k[PH3]
The half-life of PH3 is 37.9 s at 120
°
C
(i) How much time is required for ¾ th of PH3 to decompose ?
(ii) What fraction of the original sample of PH3 remains behind after 1 minute ?
2. Explain the following terms:
(i) Order of a reaction
(ii) Molecularity of a reaction
2011
3.(a) Express clearly what you understand by ‘rate expression’ and ‘rate constant’ of a
reaction.
(b) Nitrogen pentoxide decomposes according to the equation:
2N2O5(g) 4NO2(g) + O2(g)
This first order reaction was allowed to proceed at 40
°
C and the data given below were
collected:
[N2O5] M
Time (min)
0.400
0.00
0.289
20.00
0.209
40.00
0.151
60.00
0.109
80.00
(i) Calculate the rate constant for the reaction. Include units with your answer.
(ii) Calculate the initial rate of reaction.
(iii) After how many minutes will [N2O5] be equal to 0.350 M.
4.(a) Define:
(i) Order of a reaction
(ii) Elementary step in a reaction
(b) A first order reaction has a rate constant value of 0.00510 min-1. If we begin with
0.01 M concentration of the reactant, how much of the reactant will remain after
3.00 hours ?

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