Question:

At \(27^\circ C\), a real gas of molar mass \[ 44\ \text{g mol}^{-1} \] occupies a volume of \[ 0.4\ \text{L} \] at a pressure of \[ 40\ \text{atm}. \] If the compressibility factor is \[ Z=0.65, \] what is its weight (in g)? \[ (R=0.082\ \text{L-atm K}^{-1}\text{mol}^{-1}) \]

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For real gases: \[ PV=ZnRT. \] If \(Z\lt 1\), intermolecular attractions dominate. Always calculate moles using \[ n=\frac{PV}{ZRT} \] before finding the mass.
Updated On: Jul 29, 2026
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The Correct Option is B

Solution and Explanation

Concept: For a real gas, \[ PV=ZnRT \] where \[ Z=\text{compressibility factor}. \] Hence, \[ n=\frac{PV}{ZRT}. \] Mass of gas: \[ m=nM, \] where \(M\) is the molar mass.

Step 1: Calculate the number of moles. Given, \[ P=40\ \text{atm}, \] \[ V=0.4\ \text{L}, \] \[ T=27^\circ C=300\ \text{K}, \] \[ Z=0.65, \] \[ R=0.082\ \text{L-atm K}^{-1}\text{mol}^{-1}. \] Therefore, \[ n = \frac{PV}{ZRT} = \frac{40\times0.4} {0.65\times0.082\times300}. \] \[ = \frac{16}{15.99} \approx1. \] \[ n\approx1\ \text{mol}. \]

Step 2: Calculate the mass of the gas. Given molar mass, \[ M=44\ \text{g mol}^{-1}. \] Thus, \[ m=nM. \] \[ m=(1)(44). \] \[ m=44\ \text{g}. \]

Final Answer: \[ \boxed{44\ \text{g}} \] \[ \boxed{\text{Answer = (B)}} \]
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