Question

The volume occupied by 4.75 g of acetylene gas at 50 °C and 740 mmHg pressure is _______ L. (Rounded off to the nearest integer) [Given \( R = 0.0826 \, \text{L atm K}^{-1} \text{ mol}^{-1} \)]

Hint:

Ensure $P$ is in atmospheres (divide mmHg by 760) and $T$ is in Kelvin before using $R = 0.0821$ or $0.0826$.

Answer 1

Correct Answer: 5

Step 1: Ideal gas law is $PV = nRT$. Acetylene is $C_2H_2$ (Molar mass $= 26 \text{ g/mol}$).
Step 2: $n = \frac{4.75}{26} \approx 0.1827 \text{ mol}$.
Step 3: $P = \frac{740}{760} \text{ atm} \approx 0.9737 \text{ atm}$.
Step 4: $T = 50 + 273 = 323 \text{ K}$.
Step 5: $V = \frac{nRT}{P} = \frac{0.1827 \times 0.0826 \times 323}{0.9737} \approx \frac{4.874}{0.9737} \approx 5.005 \text{ L}$. Rounding to the nearest integer, $V = 5 \text{ L}$.