- #1
MexChemE
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Homework Statement
Consider an ideal gas with [itex]C_V=6.76 \frac{cal}{mol \cdot K}[/itex]. Calculate [itex]\Delta H[/itex] and [itex]\Delta U[/itex] when ten moles of this gas are heated from 273.15 K to 373.15 K.
Homework Equations
[tex]\Delta H = \Delta U + P\Delta V[/tex]
[tex]Q=n C_V \Delta T[/tex]
The Attempt at a Solution
As I'm given the heat capacity at constant volume I'm assuming this is an isochoric process. That means [itex]W=0[/itex]. Therefore, [itex]\Delta U=Q[/itex].
[tex]\Delta U=Q= (10 \ mol) \left(6.76 \frac{cal}{mol \cdot K} \right) (100 \ K) = 6760 \ cal[/tex]
Now, for the change in enthalpy we have:
[tex]\Delta H = 6760 \ cal + P\Delta V[/tex]
This is where I'm having trouble. Should I cancel the second term in the above equation? And so have: [itex]\Delta H=\Delta U[/itex]. But, if the gas is heated at constant volume pressure should increase, that means I should consider the PV term in the last equation. I wasn't provided with initial or final values for pressure and volume, so there's not enough information to use PV=nRT. What should I do?