Assertion (A): Methanol is highly toxic and can cause blindness if ingested. Reason (R): Methanol is metabolized in the body to formaldehyde and formic acid. MCQ with Answer and Explanation

Assertion (A): Methanol is highly toxic and can cause blindness if ingested. Reason (R): Methanol is metabolized in the body to formaldehyde and formic acid.
A. Both A and R are true but R is NOT the correct explanation of A.
B. A is true but R is false.
C. A is false but R is true.
D. Both A and R are true and R is the correct explanation of A.
Answer: Option D
Solution (By JKSSB Mock Tests)
Methanol (wood alcohol) is highly toxic. When ingested, it is metabolized by the enzyme alcohol dehydrogenase into formaldehyde and then formic acid. Formic acid interferes with mitochondrial function, leading to metabolic acidosis, optic nerve damage, and blindness. Both statements are correct and R explains A.

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The ignition temperature of a fuel is:
A. The temperature at which it boils.
B. The highest temperature it can reach.
C. The lowest temperature at which it catches fire.
D. The temperature at which it melts.

Correct Answer: Option C


Explanation:
The ignition temperature (or kindling temperature) is the minimum temperature to which a fuel must be heated so that it catches fire and starts burning spontaneously. A lower ignition temperature means the fuel is more highly flammable and can ignite more easily at ambient conditions.

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Which of the following contains a coordinate bond?
A. H₂O
B. O₃
C. NH₃
D. NaCl

Correct Answer: Option B


Explanation:
Ozone (O₃) has a coordinate bond (dative bond). One oxygen atom donates a lone pair to another oxygen atom. The Lewis structure shows O=O⁺–O⁻ or resonance. NaCl is ionic; H₂O has polar covalent bonds; NH₃ has ordinary covalent bonds (though it can donate a lone pair to form coordinate bond in NH₄⁺).

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Question #3
An atom of element X has 6 protons and 8 neutrons. Its mass number is:
A. 14
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Correct Answer: Option A


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Mass number = protons + neutrons = 6 + 8 = 14. This corresponds to carbon-14 isotope. Atomic number = 6 (carbon).

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