JEE Main 2023 · 1 February · morning · Single correct · +4 / −1
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R
Assertion A : Hydrogen is an environment friendly fuel.
Reason R : Atomic number of hydrogen is 1 and it is a very light element.
In the light of the above statements, choose the correct answer from the options given below :
- (a) Both A and R are true but R is NOT the correct explanation of A
- (b) A is false but R is true
- (c) A is true but R is false
- (d) Both A and R are true and R is the correct explanation of A
Answer and solution
Answer (a) Both A and R are true but R is NOT the correct explanation of A
Solution
Chemistry ma’am · 4 steps
Both lines are true, but ask what hydrogen leaves behind when it burns, not how light it is.
- Check A. Hydrogen burns to give only water: 2H₂ + O₂ → 2H₂O. No CO₂, no soot and no sulphur oxides form, so A is true.
- Check R. Hydrogen has atomic number 1 and is the lightest element, so R is true as well.
- Does R explain A. Hydrogen is clean because its only combustion product is water. Being light or having atomic number 1 says nothing about what the exhaust contains, so R does not explain A.
- So. Both statements are true, but R is not the correct explanation of A. The answer is (a).
The idea to keep. In assertion-reason questions, test each statement on its own first. Then ask whether R is the actual cause of A. A true fact that sits nearby is not an explanation.
Answer from the NTA final answer key. Solution by PrepWiser.