Statement I: The reactions having low value of activation energy are generally fast.

Statement II: Temperature coefficient for reactions having low activation energy is large.

Statement I is true but statement II is false

The correct answer is option 3. Statement I is true but statement II is false.

Let us delve into each statement and its implications:

Statement I: The reactions having low value of activation energy are generally fast.

Activation energy is the minimum amount of energy required for a chemical reaction to occur. Reactions with low activation energy require less energy input to initiate the reaction, which means they can proceed more readily and at a faster rate compared to reactions with higher activation energies. This is because a lower activation energy barrier allows a larger portion of the reacting molecules to possess the required energy to overcome it, leading to more frequent collisions and successful reactions. As a result, reactions with low activation energy often exhibit faster reaction rates.

For example, consider the decomposition of hydrogen peroxide \((H_2O_2)\) into water \((H_2O)\) and oxygen \((O_2)\). This reaction has a relatively low activation energy, which enables it to occur spontaneously, leading to the rapid decomposition of hydrogen peroxide.

Statement II: Temperature coefficient for reactions having low activation energy is large.

The temperature coefficient measures the rate of change of the reaction rate with temperature. It indicates how much the reaction rate increases or decreases with a change in temperature. For reactions with low activation energy, small changes in temperature can significantly affect the reaction rate, leading to a large temperature coefficient.

However, this statement is not universally true. While some reactions with low activation energy may indeed have a large temperature coefficient, this is not a defining characteristic of all such reactions. The temperature coefficient can vary depending on several factors, including the specific reaction kinetics, the presence of catalysts, and the overall reaction conditions. Therefore, it's possible for reactions with low activation energy to exhibit a small or moderate temperature coefficient, depending on these factors.

For instance, consider the reaction between hydrogen gas \((H_2)\) and iodine gas \((I_2)\) to form hydrogen iodide gas \((HI)\). This reaction has a relatively low activation energy, yet its temperature coefficient may not necessarily be large, especially if other factors such as equilibrium constraints or the presence of a catalyst influence the reaction rate's sensitivity to temperature changes.

In summary, while reactions with low activation energy tend to be fast due to their lower energy barrier, the temperature coefficient for such reactions can vary and may not necessarily be large. Therefore, Statement I is true, but Statement II is false.