Save
...
Topic 16: Kinetics II
16.4 The Arrhenius Equation
16.4.1 Temperature Dependence of Rate Constants
Save
Share
Learn
Content
Leaderboard
Share
Learn
Cards (96)
As temperature rises, the rate constant increases, leading to a faster
reaction rate
.
What does the pre-exponential factor (
A
A
A
) represent in the Arrhenius equation?
Collision frequency
In the Arrhenius equation, the activation energy (
E
a
E_{a}
E
a
) is the minimum energy needed for a reaction to occur.
What is the value of the gas constant (R</latex>) in the Arrhenius equation?
8.314
J
m
o
l
−
1
K
−
1
8.314 \, J \, mol^{ - 1} \, K^{ - 1}
8.314
J
m
o
l
−
1
K
−
1
If
A
=
A =
A
=
1.5
×
1
0
8
s
−
1
1.5 \times 10^{8} s^{ - 1}
1.5
×
1
0
8
s
−
1
,
E
a
=
E_{a} =
E
a
=
50
k
J
/
m
o
l
50 kJ / mol
50
k
J
/
m
o
l
, and
T
=
T =
T
=
300
K
300 K
300
K
, then
k
≈
1.3
×
1
0
4
s
−
1
k \approx 1.3 \times 10^{4} s^{ - 1}
k
≈
1.3
×
1
0
4
s
−
1
.
What is the role of the pre-exponential factor (
A
A
A
) in the Arrhenius equation?
Frequency of collisions
The activation energy (
E
a
E_{a}
E
a
) is the minimum energy needed for a reaction to reach the transition state.
What are the units of the activation energy (
E
a
E_{a}
E
a
) in the Arrhenius equation?
J/mol
The activation energy (
E
a
E_{a}
E
a
) is necessary for breaking existing bonds and forming new ones in a chemical reaction.
What does the frequency factor (
A
A
A
) measure in the Arrhenius equation?
Effective collisions
In the Arrhenius equation, the frequency factor (
A
A
A
) directly influences the rate constant.
What does the frequency factor (A) in the Arrhenius equation represent?
Effective collision frequency
In the Arrhenius equation,
A
A
A
directly influences the rate constant.
The frequency factor (A) has fixed units.
False
Steps to calculate the rate constant using the Arrhenius equation
1️⃣ Identify the variables:
A
,
E
a
,
R
,
T
A, E_{a}, R, T
A
,
E
a
,
R
,
T
2️⃣ Convert temperature to Kelvin:
T
(
K
)
=
T(K) =
T
(
K
)
=
T
(
∘
C
)
+
T(^{\circ}C) +
T
(
∘
C
)
+
273.15
273.15
273.15
3️⃣ Apply the Arrhenius equation:
k
=
k =
k
=
A
×
e
−
E
a
/
(
R
×
T
)
A \times e^{ - E_{a} / (R \times T)}
A
×
e
−
E
a
/
(
R
×
T
)
4️⃣ Calculate the rate constant
k
k
k
What is the rate constant if
A
=
A =
A
=
1.5
×
1
0
8
s
−
1
1.5 \times 10^{8} s^{ - 1}
1.5
×
1
0
8
s
−
1
,
E
a
=
E_{a} =
E
a
=
50
k
J
/
m
o
l
50 kJ / mol
50
k
J
/
m
o
l
, and
T
=
T =
T
=
300
K
300 K
300
K
?
1.3
×
1
0
4
s
−
1
1.3 \times 10^{4} s^{ - 1}
1.3
×
1
0
4
s
−
1
The rate constant is a proportionality constant that relates the rate of a reaction to the concentrations of the
reactants
.
The rate constant depends on the concentration of reactants.
False
Match the variable with its unit in reaction kinetics:
Rate ↔️ M/s
Rate Constant ↔️ Varies
Concentration ↔️ M
What happens to the rate constant as temperature increases?
It increases
The relationship between the rate constant and temperature is described by the Arrhenius
equation
.
Higher temperature provides more molecules with sufficient energy to overcome the
activation energy
barrier.
Match the variable in the Arrhenius equation with its unit:
Activation Energy ↔️ J/mol
Gas Constant ↔️
8.314
J
m
o
l
−
1
K
−
1
8.314 \, J \, mol^{ - 1} \, K^{ - 1}
8.314
J
m
o
l
−
1
K
−
1
Temperature ↔️ Kelvin
What is the Arrhenius equation?
k
=
k =
k
=
A
e
−
E
a
/
R
T
Ae^{ - Ea / RT}
A
e
−
E
a
/
RT
The rate constant
k
k
k
is a measure of the reaction rate at a specific temperature.
What is the rate constant
k
k
k
a measure of in the Arrhenius equation?
Reaction rate at temperature
The pre-exponential factor
A
A
A
represents the frequency of successful collisions
What is the full Arrhenius equation?
k
=
k =
k
=
A
e
−
E
a
/
R
T
Ae^{ - E_{a} / RT}
A
e
−
E
a
/
RT
The activation energy
E
a
E_{a}
E
a
is the minimum energy needed for the reaction
What is the rate constant (k) defined as?
Proportionality constant
The rate constant is dependent on reactant concentrations.
False
The rate equation is given by
R
a
t
e
=
Rate =
R
a
t
e
=
k
[
A
]
m
[
B
]
n
k[A]^{m}[B]^{n}
k
[
A
]
m
[
B
]
n
, where
k
k
k
is the rate constant.
How does temperature affect the rate constant (k)?
Increases with temperature
The Arrhenius equation is
k
=
k =
k
=
A
e
−
E
a
/
R
T
Ae^{ - E_{a} / RT}
A
e
−
E
a
/
RT
.
What is the gas constant (R) used in the Arrhenius equation?
8.314 J mol^{ - 1} K^{ - 1}
In the Arrhenius equation,
T
T
T
represents the temperature in Kelvin.
Match the terms in the Arrhenius equation with their meanings:
A
A
A
↔️ Pre-exponential factor
E
a
E_{a}
E
a
↔️ Activation energy
R
R
R
↔️ Gas constant
T
T
T
↔️ Temperature in Kelvin
What happens to the reaction rate as the rate constant increases?
Becomes faster
The reaction rate decreases as the rate constant increases.
False
Steps involved in using an Arrhenius plot to determine the activation energy (Ea):
1️⃣ Plot
ln
k
\ln k
ln
k
against
1
/
T
1 / T
1/
T
2️⃣ Determine the gradient of the line
3️⃣ Multiply the gradient by
R
R
R
4️⃣ Change the sign to obtain
E
a
E_{a}
E
a
See all 96 cards