I was doing a question on thermodynamics and came across this one stating
During isothermal expansion of gas of an ideal gas :
a) Internal energy decreases
b) Enthalpy increases
c) Enthalpy reduces to zero
d) Enthalpy remains unchanged
I cannot agree to any of these as $\Delta H = \Delta U + W$, $\Delta U = 0$ as $\Delta T = 0$ but $W \neq 0$ so $\Delta H = W$ which is $\neq 0$ and as $W \lt 0$ the enthalpy should decrease but how much how do I know and to add to the confusion the answer given is enthalpy remains unchanged in the light of the equation $\Delta H = \Delta U +\Delta n_\mathrm gRT$ and $\Delta U$ and $\Delta n = 0$ so $\Delta H = 0$ is it right.