Question

Is activation energy negative or positive?

Answer 1

Hint: Activation energy is the minimum amount of extra energy which is needed by a reacting molecule for getting converted into a product. This is the energy which energizes molecules or atoms so that they can undergo a chemical reaction. SI unit of activation energy is kilo calorie per mol. The formula which is used to find the value of activation energy is, $$\text{K }=\text{ A}{{\text{e}}^{-E_a}}^{/RT}$$
K is rate constant, A is Arrhenius constant, R is gas constant.

Complete answer:
The energy changes that outcome from a reaction can be positive, negative or even zero. Before any reaction, an energy barrier should be resolved in both situations. In some cases, when temperature increases, the reaction rates decrease. Normally, elementary reactions which show negative activation energies are mainly barrierless reactions. The mechanism of reaction depends on the capture of the potential wall. Activation energy does not depend on the temperature, pressure, volume, concentration or the coefficient of reactant.

Note:
There are some factors that can affect the activation energy. Those are,
-Nature of reactants – for ionic reactants the value of activation energy will become low because an attraction is there between reacting species. But in the reaction of covalent reactant the activation energy values will be high because to break the older bonds energy is required.
-Effect of catalyst - positive catalysts give alternative paths in which the value of activation energy will be low but the negative catalysts give an alternative path in which the value of activation energy will be high.