Question

Two chemical species $\mathrm{X}$ and $\mathrm{Y}$ combine together to form a product $\mathrm{P}$ which contains both $\mathrm{X}$ and $\mathrm{Y}$, $\mathrm{X}+\mathrm{Y}\to \mathrm{P}$. $\mathrm{X}$ and $\mathrm{Y}$ cannot be broken down into simpler substances by simple chemical reactions. Which of the following concerning the species $\mathrm{X}$, $\mathrm{Y}$, and $\mathrm{P}$ are correct?

(i) $\mathrm{P}$ is a compound

(ii) $\mathrm{X}$ and $\mathrm{Y}$ are compounds

(iii) $\mathrm{X}$ and $\mathrm{Y}$ are elements

(iv) $\mathrm{P}$ has a fixed composition

• A. (i), (ii) and (iii)
• B. (i), (ii) and (iv)
• C. (ii), (iii) and (iv)
• D. (i), (iii) and (iv)

Answer 1

The correct option is D

(i), (iii) and (iv)

Explanation:

Elements:

• An element is a pure substance that cannot be broken down into simpler substances by chemical reactions.
• Elements can be metals or non-metals or metalloids.
• Examples of elements are Iron $\left(\mathrm{Fe}\right)$, Sodium $\left(\mathrm{Na}\right)$, Gold $\left(\mathrm{Au}\right)$ etc.

Compounds:

• A compound is a pure substance composed of two or more elements, chemically combined with one another in a fixed proportion.
• The composition of a compound is always fixed.
• Examples of compounds are Sodium chloride $\left(\mathrm{NaCl}\right)$, Water $\left({\mathrm{H}}_2\mathrm{O}\right)$.

In a reaction, elements react to form compounds.

The given reaction is: $\underset{\mathrm{Elements}}{\mathrm{X}+\mathrm{Y}}\to \underset{\mathrm{Compound}}{\mathrm{P}}$

In the above reaction, $\mathrm{X}\mathrm{and}\mathrm{Y}$ are elements while $\mathrm{P}$ is the compound and it has a fixed composition.

Hence, the correct option is D i.e. (i), (iii) and (iv).