Question

What is the effect of temperature on reaction rate? What is Arrhenius equation?

Hint:

Higher temperature → more molecules cross activation energy barrier → faster reaction rate. Arrhenius plot helps find $E_a$.

Answer 1

Step 1: Effect of temperature on reaction rate.
The rate of a chemical reaction generally increases with an increase in temperature. Usually, a rise of 10°C doubles or triples the rate of reaction.
Step 2: Reason.
When temperature increases, the kinetic energy of molecules also increases. This leads to more effective collisions between reactant molecules that have energy equal to or greater than the activation energy.
Step 3: Explanation using collision theory.
Only those collisions that occur with sufficient energy (≥ activation energy, $E_a$) and proper orientation result in product formation. Temperature increases the fraction of molecules possessing this minimum energy.
Step 4: Arrhenius Equation.
The temperature dependence of rate constant ($k$) is expressed by Arrhenius as: \[ k = A e^{-\frac{E_a}{RT}} \] where, $k =$ rate constant, $A =$ frequency factor, $E_a =$ activation energy, $R =$ gas constant, $T =$ absolute temperature (in K).
Step 5: Logarithmic form.
Taking logarithm on both sides: \[ \log k = \log A - \frac{E_a}{2.303R} \times \frac{1}{T} \] This gives a straight line when $\log k$ is plotted against $\frac{1}{T}$ (Arrhenius plot).
Step 6: Conclusion.
Thus, the rate constant increases exponentially with temperature, leading to a faster reaction rate.