This document discusses the temperature dependence of reaction rates. It notes that increasing temperature causes an exponential increase in the reaction rate constant based on the Arrhenius equation. The Arrhenius equation quantitatively relates the reaction rate constant to temperature, the activation energy, and a frequency factor. Specifically, a higher temperature results in a higher percentage of reactant molecules possessing kinetic energy exceeding the activation energy threshold, thereby increasing the reaction rate.

1.  Name: Kumar Ashutosh
 Class: 12 ‘B’ Roll no: 3322
 Subject: Chemistry
 Topic: Temperature dependence of rate of
reaction
 Submitted to: Kapishwar Ji
Parmeshwari Devi Dhanuka Sarswati Vidya
Mandir

2.  RATE OF REACTION:
The reaction rate or rate of reaction is the speed at which a
chemical reaction takes place, defined as proportional to the
increase in the concentration of a product per unit time and to
the decrease in the concentration of a reactant per unit time.
Reaction rates can vary dramatically.
 Reactant concentration, the physical state of the reactants,
and surface area, temperature, and the presence of a
catalyst are the four main factors that affect reaction rate.
 We will discuss the about the factor of effect of temperature on
rate of reaction

3.  Temperature dependence of the rate of a reaction
 Activation energy comes into play. A reaction occurs
when the reactant molecules clash with each other,
according to collision theory. The threshold energy is
the smallest amount of energy that colliding molecules
must have in order for their collision to be effective.
 The activation energy is the lowest additional amount
of energy absorbed by the reactant molecules in order
for their energy to equal the threshold value.
 Threshold energy = Activation energy + Energy
possessed.

4.  Arrhenius equation
 The Arrhenius equation can quantitatively explain the
temperature dependency of the rate of a chemical process.
 k = Ae-Ea/RT
 The Arrhenius factor, also known as the frequency factor or
pre-exponential factor, is represented by A. Ea is the activation
energy in joules/mole, and R is the gas constant.
 The fraction of molecules with kinetic energy larger than Ea is
represented by the factor e-Ea/RT.

5.  As a result of the Arrhenius equation, it has been discovered that increasing the
temperature or decreasing the activation energy causes an increase in the
reaction rate and an exponential increase in the rate constant.
 Taking both sides of the equation’s natural logarithm
 ln k = -(Ea/RT) + ln A
 A straight line with slope is drawn when ln k vs 1/T is plotted = -(Ea/R) and
intercept = ln A
 At temperature T1, equation
 ln k1 = Ea/RT1 + ln A
 At temperature T2, equation
 ln k2 = Ea/RT2 + ln A
 For a given reaction, A is constant.
 The values of rate constants for temperatures T1 and T2 are k1 and k2,
respectively.
 Subtracting equation form,
 ln k2 – ln k1 = (Ea/RT1) – (Ea/RT2)
 ln (k2/k1) = Ea/R ((1/T1)-(1/T2))
 log k2/k1 = (Ea/2.303R) × ((1/T1)-(1/T2))
 log k2/k1 = (Ea/2.303R) × ((T2-T1)/(T1T2))

6. Graphical description of effect of temperature
Plotting a fraction of molecules with particular kinetic energy versus kinetic energy
for two distinct temperatures T1 and T2 illustrates this.
 The number of molecules having those levels of kinetic energy is
proportional to the area under the curve. At T1 and T2, the entire area is the
same.
 The fraction of molecules with kinetic energy greater than Ea at T1 and
T2 are represented by the areas (a) and (b). This means that when the
temperature rises, the percentage of molecules having energies greater than
Ea rises.
As a result, the velocity of the reaction quickens.

7.  .