Question

Consider the hypothetical reaction in which two volumes of Gas A combine with one volume of Gas B, forming two volumes of a single gaseous product, with no Gas A or Gas B remaining.
$2vol.GasA+1vol.GasB\to 2vol.$ (gaseous product)
Which of the following is a reasonable conclusion, based on these observations, concerning whether either or both of Gas A and Gas B might be diatomic?

• A. Neither Gas A nor Gas B must necessarily be diatomic.
• B. Both Gas A and Gas B must be diatomic
• C. Gas A must be diatomic; Gas B may or may not be.
• D. Gas B must be diatomic; Gas A may or may not be.

Answer 1

The correct option is D Gas B must be diatomic; Gas A may or may not be.

$\text{2 vol.}GasA+\text{1 vol. Gas B}⟶\text{2 vol.}\left(\text{gaseous product}\right)$

As per Avogadro’s hypothesis, we know that equal volumes of all gases contain equal number of molecules under identical conditions of temperature and pressure.

Thus two molecules of gas $A$ must be reacting completely with one molecule of gas $B$.

In order for one volume of gas $B$ to produce two volumes of product, $B$ must exist as diatomic molecules

We have no information regarding the nature of single gaseous product. as well as there is not enough evidence regarding gas $A$.

Hence Gas $B$ must be diatomic while Gas $A$ may or may not be.

Hence the required answer is (D).