Change in Enthelpy when Internal Energy does not Change

AI Thread Summary
In an isothermal expansion of a perfect gas, the internal energy (U) remains constant, leading to a change in enthalpy (H) of zero. The equation for enthalpy, H = U + PV, indicates that if U does not change, the change in enthalpy also depends on the change in the product of pressure and volume (PV). Since the pressure may change during expansion but the product PV does not contribute to a net change, ΔH equals zero. The confusion arises from the assumption that PΔV would be non-zero during expansion, but the overall enthalpy change remains unaffected. Thus, the conclusion is that the change in enthalpy is indeed zero during isothermal expansion.
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Homework Statement



The internal energy of a perfect gas does not change when the gas undergoes isothermal expansion. What is the change in enthalpy?

Homework Equations


H=U+PV


The Attempt at a Solution


The answer is 0

Since U, the internal energy, doesn't change, I assumed that the equation would be ΔH=PΔV. Why would PΔV equal 0 if there is an expansion (ΔV is not 0)? I'm guessing that I'm not seeing something here since this seemed to be a rather simple question.
 
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The enthalpy is actually \Delta H = \Delta U + \Delta (PV). I don't think that PV will change.
 
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