Chemistry 2002 JAMB Past Questions - Question 12: The Arrhenius equation expresses the relationship between the speed of a reaction and its

Correct Answer

A

Explanation

The Arrhenius equation expresses the relationship between the speed (rate) of a chemical reaction and its temperature. It is named after the Swedish chemist Svante Arrhenius, who proposed it in 1889. The equation is given by:

\[ k = A \cdot e^{-\frac{E_a}{RT}} \]

where:
- \( k \) is the rate constant of the reaction,
- \( A \) is the pre-exponential factor (frequency factor), which represents the rate of the reaction at an infinite temperature,
- \( E_a \) is the activation energy, which is the minimum energy required for the reaction to occur,
- \( R \) is the ideal gas constant (8.314 J/(mol·K)),
- \( T \) is the absolute temperature in kelvins.

The Arrhenius equation helps to explain the temperature dependence of reaction rates. According to the equation, as the temperature increases, the rate constant (\( k \)) increases exponentially. This is consistent with the idea that at higher temperatures, molecules have more kinetic energy and are more likely to overcome the activation energy barrier, leading to a faster reaction.

Conversely, at lower temperatures, the exponential term becomes smaller, and the rate of the reaction decreases. The Arrhenius equation is particularly useful in predicting how changes in temperature will affect reaction rates and is commonly used in the field of chemical kinetics.