Question

Assertion: $12$ parts by mass of carbon in $CO$ and $C{O}_2$ molecules combine with $16$ and $32$ parts by mass of oxygen
Reason: A given compound always contains exactly the same proportion of elements by weight

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false.
• D. If both assertion and reason are false

Answer 1

Answer: (B)

The masses of oxygen (i.e., $16g$ and $32g$ ) which combine with a fixed mass of carbon (i.e., $12g$ ) bear a simple ratio, i.e., $16:32$ or $1:2$. This explains the law of multiple proportions.
Law of definite proportions states that a given compound always contains exactly the same proportion of element by weight, irrespective of the source.