Question

TRUE or FALSE? Please explain each answer!

a) The more negative the ∆H value of a reaction the faster it is.

b) The more negative the ∆G value of a reaction the faster it is.

c) If you compare two reactions, the one with the lowest activation energy is faster (tricky!)

d) A catalyst is a substance that lowers the ∆G value of a reaction so it becomes more spontaneous.

e)Enzymes are proteins that lower the activation energies of reactions in the cell.

f) ATP hydrolysis is thermodynamically favorable but the reaction is slow in the absence of the enzyme specialized in catalyzing this reaction.

Answer 1

a) First of all, Del .H = H2 - H1, If the Del. H is < 0 , i.e negative, then the reaction is exothermic. Generally, If the reaction occurs in Exothermic condition, then the reaction could be faster. But some times even the Endothermic reaction woud be faster.

So, the answer is True.

Exothermic reaction means, the heat is leberated to the surrondings from the system (where reaction takes place).

b) Same like prrevious one, we cannot say directly whether it is true or not. But explanation below would give you the best answer.

Del. G = Del. H - (T * Del. S)

So, if more negative the Del. H, the Del. G is also more, that means the reaction is Exothermic, so the reaction is faster.

d) False. From the previous answer, Del. G = Del. H - (T * Del. S),

Therefore, Del. G only depends on change in enthalpy and entropy and temperature. But, catalyst depends on activation of energy. Catalyst will only change the reaction kinetics.

e) Yes. Enzymes that lower the activation energy of reactions in the cell. So that, it will increase the rate of a reaction, leads to make faster the reaction.