Question8 The activation energy of a reaction is: Select one alternative: the net change in free energy in an enzyme-catalysed system. negative if the reaction is energetically favourable. increased by enzymes. the energy that must be absorbed by reactants in order for the reaction to take place. lower for reactants than products. ResetMaximum marks: 1 Flag question undefined

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Question: The activation energy of a reaction is: Select one alternative: the net change in free energy in an enzyme-catalysed system. negative if the reaction is energetically favourable. increased by enzymes. the energy that must be absorbed by reactants in order for the reaction to take place. lower for reactants than products.

Option 1: 'the net change in free energy in an enzyme-catalysed system.' This describes ΔG, the overall free energy change of the reaction, not the activation energy. Activation energy is about the energy barrier to reach the transition state, not the final energy difference.

Option 2: 'negative if the reaction is energetically favourable.' This statement concerns ΔG signs for spontaneous or energetically favorable reactions, not activation energy. Activation energy does not become negative; it’s a barrier that must be overcome regardless of overall ΔG.

Option 3: 'increased by enzymes.' Enzymes lower the activation energy, thereby increasing the rate of the reaction. This option is incorrect because enzymes decrease, not increase, the activation energy.

Option 4: 'the energy that must be absorbed by reactants in order for the reaction to take place.' This captures the essence of activation energy: the minimum energy input required to reach the transition state so the reaction can proceed.

Option 5: 'lower for reactants than products.' Activation energy is not defined as being lower for reactants versus products; it is a barrier for the reactants to convert to products and does not compare energy levels of reactants and products in that way.

In summary, the activation energy is the energy threshold that reactants must acquire to reach the transition state and start the reaction, which is correctly described by option 4. The other choices describe related concepts (ΔG, enzyme effects on Ea, general misinterpretations) but do not define activation energy itself.

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