An ideal gas A and a real gas B have their volumes increased from V to 2V under isothermal conditions. The increase in internal energy:
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An ideal gas A and a real gas B have their volumes increased from V to 2V under isothermal conditions. The increase in internal energy:

G1 Physics · Accepted Answer

Step 1: Both gases are expanded isothermally (T = constant). Step 2: For IDEAL gas A, U depends only on T. Thus the change in internal energy for gas A is ΔU = 0. Step 3: For REAL gas B, intermolecular potential energy can change when intermolecular separation changes, even while T stays constant. Step 4: Consequently the change ΔU for gas B is not generally zero. Its sign and magnitude require a real-gas model. Step 5: For example, an attractive van der Waals gas has (∂U/∂V) at constant T = an…