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141. What is meant by the ‘rate constant’ K of a reaction? If the concentration be expressed in mol L^–1 units and time in seconds, what would be the units for K

(i) for a zero order reaction
(ii) for a first order reaction?

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Long Answer Type

142. For the reaction
: 2A + B + C → A₂B
the rate = k[A] [B]² with k = 2.0 x 10^–6 mol^–2L²s^–1.
Calculate the initial rate of the reaction when [A] = 0.1 mol L^-1, [B] = 0.2 mol L^-1and [C] = 0.8 M. Calculate the rate of reaction after [A] is reduced to 0.06 mol L^–1.

263 Views

Short Answer Type

143. The decomposition of NH₃ on platinum surface is zero order. What are the rates of production of N₂ and H₂ if k = 2.5 x 10^–4 mol^–1Ls^–1?

173 Views

144. In a pseudo first order hydrolysis of ester in water the following results were obtained:

t / s	0	30	60	90
Ester / mol L^–1	0.55	0.31	0.17	0.085

(i) Calculate the average rate of reaction between the time interval 30 to 60 seconds.
(ii) Calculate the pseudo first order rate constant for the hydrolysis of ester.

336 Views

Long Answer Type

145. In a reaction between A and B, the initial rate of reaction (r₀) was measured for different initial concentrations of A and B as given below:

A/mol L^–1	0.20	0.20	0.40
B/mol L^–1	0.30	0.10	0.05
r/mol L^–1S^–1	5.07 x 10^–5	5.07 x 10^–5	1.43 x 10^–4

What is the order of the reaction with respect of A and B?

142 Views

146. The following results have been obtained during the kinetic studies of the reaction:

2A + B → C + D

exp.	[A]/ mol L^–1	[B]/M	Initial rate of formation of D/mol L^–1 min^–1
I	0.1	0.1	6.0 x 10^–3
II	0.3	0.2	7.2 x 10^–2
III	0.3	0.4	2.88 x 10^–1
IV	0.4	0.1	2.40 x 10^–2

Determine the rate law and the rate constant for the reaction.

153 Views

147. e 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:

exp.

[A]/
mol L^–1

[B]/M

Initial rate of formation
of D/mol L^–1 min^–1

I

0.1

0.1

2.0 x 10^–2

II

-

0.2

4.0 x 10^–2

III

0.4

0.4

-

IV

-

0.2

2.0 x 10^–2

Rate law for the reaction is given by:
Rate = k [A]¹ [B]⁰ = k[A]
2.0 x 10^–2 mol L^–1 min^–1 = k[0.1 mol L^–1]
Rate constant,

$k = \frac{2.0 \times 10^{- 2} mol L^{- 1} \min^{- 1}}{0.1 mol L^{- 1}} or$

Rate constant = k = 0.2 min^–1.
(i) In experiment II Rate = k[A]

$[A] = \frac{rate}{k}$

$= \frac{4.0 \times 10^{- 2} M \min^{- 1}}{0.2 \min^{- 1}} = 0.20 M$

(ii) In experiment III

Rate = k[A]
= 0.2 min^–1 x 0.4 M
= 0.08 min^–1= 8.0 x 10^–2 M min^–1(iii) In experiment IV

Rate = k[A]

$[A] = \frac{rate}{k} = \frac{2.0 \times 10^{- 2} M \min^{- 1}}{0.2 \min^{- 1}} = 0.1 M$

Thus the completed table is

exp.	[A]/ mol L^–1	[B]/M	Initial rate of formation of D/mol L^–1 min^–1
I	0.1	0.1	2.0 x 10^–2
II	0.2	0.2	4.0 x 10^–2
III	0.4	0.4	8.0 x 10^-2
IV	0.1	0.2	2.0 x 10^–2

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148. 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

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149. The experimental data for decomposition of N₂O₅ [2N₂O_s → 4NO₂ + O₂] in gas phase at 318 k are given below:

(a) Plot [N₂O₅] again t.
(b) Find the half life period for the reaction.
(c) Draw a graph between log [N₂O₅] and t.
(d) What is rate law?
(e) Calculate the rate constant.
(f) Calculate the half life period from K and compare it with (ii).

428 Views

Short Answer Type

150. 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 ?

375 Views