The activation energy of a reaction can be determined from the slope of which of the following graphs?
A
ln k vs. $${1 \over T}$$
B
$${T \over {\ln \,k}}$$ vs. $${1 \over T}$$
C
ln k vs. $$T$$
D
$${{\ln k} \over T}$$ vs. $$T$$
Explanation
According to Arrhenius equation,
$$k = A{e^{ - {{{E_a}} \over {ET}}}}$$
Taking natural log on both the sides we get,
ln k = ln A $${ - {{{E_a}} \over {ET}}}$$ ...........(1)
Comparing (1) with standard form of equation of
line
y = mx + C
We get Slope, m = $${ - {{{E_a}} \over R}}$$
Hence, if ln k is plotted
against 1/T, slope of the line will be $${ - {{{E_a}} \over R}}$$.
2
AIPMT 2015
MCQ (Single Correct Answer)
The rate constant of the reaction A $$ \to $$ B is 0.6 $$ \times $$ 10$$-$$3 mol L$$-$$1 s$$-$$1. If the concentration of A is 5 M, then concentration of B after 20 minutes is
A
3.60 M
B
0.36 M
C
0.72 M
D
1.08 M
Explanation
For zero order reaction unit of rate constant is
mole per second.
$$ \therefore $$ For zero order
x = kt
$$ \Rightarrow $$ x = 0.6 × 10–3 × 20 × 60 = 0.72 M
3
NEET 2013 (Karnataka)
MCQ (Single Correct Answer)
A reaction is 50% complete in 2 hours and 75% complete in 4 hours. The order of reaction is
A
1
B
2
C
3
D
0
Explanation
For a first order reaction,
t75% = 2 $$ \times $$ t50%
4
NEET 2013
MCQ (Single Correct Answer)
What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20oC to 35oC?
(R = 8.314 J mol$$-$$1 K$$-$$1)