Question

The density of a gas is \( 1.964 \text{ g/dm}^{3} \) at \( 273 \text{ K} \) and \( 76 \text{ cm Hg} \). The gas is:

• A. $CH_{4}$
• B. $C_{2}H_{6}$
• C. $CO_{2}$
• D. $Xe$

Hint:

At STP, Molar Mass = Density $\times$ 22.4.

Answer 1

The Correct Option is C

Step 1: Concept
Use the ideal gas equation: $PV = nRT = \frac{w}{M}RT$, which gives $M = \frac{dRT}{P}$.
Step 2: Analysis
$d = 1.964 g/L$, $R = 0.0821 L\cdot atm/K\cdot mol$, $T = 273 K$, $P = 1 atm$.
$M = \frac{1.964 \times 0.0821 \times 273}{1} \approx 44$.
Step 3: Conclusion
The molar mass of $CO_{2}$ is $44 g/mol$.
Final Answer: (C)