Question

Equal volumes of oxygen gas and a second gas weigh 1.00 and 2.375 grams respectively under the same experimental conditions. Which of the following is the unknown gas?

• A. $NO$
• B. $S{O}_2$
• C. $C{S}_2$
• D. $CO$

Answer 1

The correct option is C $C{S}_2$

Let’s take ‘V’ litres of both the gases at STP
Moles of $O_2=\frac{V}{22.4}$.
It is given that it weighs $1\text{g}$
Moles = $\frac{1}{32}$
From the above calculations we can say that,
$\frac{V}{22.4}=\frac{1}{32}\Rightarrow V=\frac{22.4}{32}$

For the unknown gas we can write,
Moles = $\frac{V}{22.4}$
Also,
Moles = $\frac{2.375}{M}$

$\frac{2.375}{M}=\frac{V}{22.4}$

Substituting the value of $V$ from above,

$\frac{2.375}{M}=\frac{1}{32}$

$M=76$
A molar mass of 76 g/mol is possible only for $C{S}_2$ gas.