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Chemical Kinetics
Long Answer Type
151.
The gas phase decomposition of dimethyl ether follows first order kinetics:
CH
3
– O CH
3
(g) → CH
4
(g) + H
2
(g) + CO(g)
The reaction is carried out in a constant volume container at 500°C and has a half life of 14.5 minutes. Initially only dimethyl ether is present at a present of 0.40 atmosphere. What is the total pressure of the system after 12 minutes?
(Assume ideal gas behaviour).
602 Views
152.
The half-life for radioactive decay of
14
C
is 5730 years. An archaeological artifact containing wood had only 80% of the
C
14
activity found in living tree. Estimate the age of the sample or calculate the age of the artefact.
219 Views
153.
During nuclear explosion, one of the products is
90
Sr with half-life of 28.1 Years. If 1 μg of
90
Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 years and 60 years if it is not lost metabolically.
202 Views
Short Answer Type
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154.
A first order decomposition reaction takes 40 minutes for 30% of decomposition. Calculate t
1/2
value for it.
For the first order reaction
K
=
2
.
303
t
log
a
a
-
x
=
2
.
303
40
log
100
70
=
2
.
303
40
log
100
-
log
70
=
2
.
303
40
(
2
-
1
.
8808
)
=
2
.
303
40
×
0
.
1192
=
0
.
0068
min
-
1
(
ii
)
0
.
0068
=
2
.
303
t
log
100
50
0
.
0068
=
2
.
303
t
log
2
0
.
0068
=
2
.
303
t
×
0
.
3010
t
=
2
.
303
×
0
.
3010
0
.
0068
=
101
.
94
min
.
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Long Answer Type
155.
For first order reaction show that time required for 99% completion is twice the time required for the completion of 90% of reaction.
826 Views
Short Answer Type
156.
A first order reaction has a specific reaction rate of 2.31 x 10
–3
sec
–1
. Calculate the half-life period of the reaction.
197 Views
157.
The difference in energy of activation for uncatalysed reaction and catalysed reaction is 20 kJ/mol. How many times the rate constant of catalysed reaction will increase over the uncatalysed reaction?
117 Views
158.
Show that the time required for the completion of 3/4th reaction of first order is twice the time required for completion of 1/2 of the reaction.
333 Views
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159.
If half-life of a first order reaction involving reactant A is 5 min. How long will it take [A] to react 25% of its initial concentration?
125 Views
160.
A first order reaction is 15% complete in 20 minutes. How long will it take to be 60% completed ?
695 Views
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