Question

1) For the formation of 1 mol of nitrosyl chloride at a given temperature, ΔH = –36kJ.

NO(g) + 1/2 Cl₂(g) → NOCl(g)

The activation energy for this reaction is 67 kJ/mol. What is the activation energy for the reverse reaction?

2) Below is a proposed mechanism for the decomposition of H₂O₂.

H2O2 + I– ® H2O + IO–	slow
H2O2 + IO– ® H2O + O2 + I–	fast

Which of the following statements is incorrect?

a.	I– is a catalyst.
b.	IO– is a catalyst.
c.	The net reaction is 2H2O2 ® 2H2O + O2.
d.	All of the above are correct.
e.	All of the above are incorrect.

Answer 1

ANS1.

from the above graph, E_F represents activation energy of forward reaction whereas ER represents activation energy of backward reaction as you can see that

E_R=E_F + DELTA H that means we need to add the energy present in reactants ie delta H to the activation energy required by the reactants to cross the barrier and convert to the product.

E_R= 67+(-36)

E_R= 31kJ/mol

2) Statements b and d are incorrect

as you can see it is decomposition of H₂O₂ where I acts as a catalyst because it is obtained in the product as it is. It has not been used here I catalyse the decomposition by altering the rate of reaction.

Secondly, IO is an intermediate formed by the catalyst with the reactant which further reacts and forms water and oxygen hence we cannot see IO in product.Since we have not added IO like I at the beginning of reaction nor it is obtained in product hence we can say that IO is just a catalyst which is formed and consumed in the reaction.HENCE SECOND STATEMENT IS INCORRECT.

which makes the net reaction that is decomposition of 2H₂O_{2 -------}2H₂O+O _2.