Question:-
Assertion (A): In a three-way catalytic converter for emission control in S.I. Engines, conversion of NOx has to precede the oxidation of HC and CO.
Reason (R): A reducing atmosphere is essential for the conversion of NOx.
Option (A)
Both A and R are individually true and R is the correct explanation of A
Option (B)
Both A and R are true but R is not the correct explanation of A
Option(C)
A is true but R is false
Option(D)
A is false but R is true
Correct Option:
(A)
Question Solution:

Reduction of NOx liberates O2 which is used for oxidation (in addition to external source) So it should always before oxidation.
question-answer-faq-9152