Recent content by patrickmoloney

  1. patrickmoloney

    Optimizing Refrigerator Efficiency: Solving for Necessary Power Draw

    Yeah I think I'll do it algebraically so until the final line. Thanks very much.
  2. patrickmoloney

    Optimizing Refrigerator Efficiency: Solving for Necessary Power Draw

    Homework Statement Suppose that heat leaks into your kitchen refrigerator at an average rate of 300W. Assuming ideal operation, how much power must it draw from the wall. Homework Equations \eta = \dfrac{T_C}{T_H - T_C} W= \dfrac{Q}{COP} The Attempt at a Solution A typical refrigerator...
  3. patrickmoloney

    Relation between heat capacities and van der Waals equation

    I got it from T \Bigg{(}\dfrac{\partial p}{\partial T}\Bigg{)}_V I couldn't get an R on its own
  4. patrickmoloney

    Relation between heat capacities and van der Waals equation

    I got \dfrac{RT}{1-\frac{2a}{V^3}\frac{(V-b)^2}{RT}}. But I'm happy enough that I know how to solve the problem should it come up. Thanks guys.
  5. patrickmoloney

    Relation between heat capacities and van der Waals equation

    Ok I've tried it using your fraction and got \dfrac{RV(V-b)}{4a(\frac{b}{V}-1)} I've just realized how bad I am at algebra.
  6. patrickmoloney

    Relation between heat capacities and van der Waals equation

    I was thinking cause ] Yeah I would love that in the end I got \dfrac{T^2(2a-1)}{V^3(V-b)} which looks respectable. It's not a homework problem anyway but it was from an exam paper which means it could be something that could come up in the exam. Would you be able to teach the method chester...
  7. patrickmoloney

    Relation between heat capacities and van der Waals equation

    \Bigg{(}\dfrac{\partial T}{\partial V}\Bigg{)}_p = -\Bigg{(}\dfrac{2ab}{V^3} +\dfrac{a}{V^2}- P\Bigg{)} \cdot \dfrac{1}{R} Letting p = \dfrac{RT}{(v-b)}-\dfrac{a}{V^2} and substituting into my equation for \Bigg{(}\dfrac{\partial T}{\partial V}\Bigg{)}_p gives \Bigg{(}\dfrac{\partial...
  8. patrickmoloney

    Relation between heat capacities and van der Waals equation

    I got \Bigg{(}\dfrac{\partial T}{\partial V}\Bigg{)}_p = -\Bigg{(}\dfrac{2ab}{V^3} +\dfrac{a}{V^2}- P\Bigg{)} \cdot \dfrac{1}{R} Then inverting this equation yields \Bigg{(}\dfrac{\partial V}{\partial T}\Bigg{)}_p = -\Bigg{(}\dfrac{V^3}{2ab} +\dfrac{V^2}{a}-\dfrac{1}{P}\Bigg{)} \cdot R
  9. patrickmoloney

    Relation between heat capacities and van der Waals equation

    Van der waals equation of state. Like I did with \Bigg{(}\dfrac{\partial p}{\partial T}\Bigg{)}_V
  10. patrickmoloney

    Relation between heat capacities and van der Waals equation

    Would that mean I could do \Bigg{(}\dfrac{\partial T}{\partial V}\Bigg{)}_p to solve the VDW equation?
  11. patrickmoloney

    Relation between heat capacities and van der Waals equation

    Differentiating the LHS with respect to T and keeping the volume constant I get \Bigg{(}\dfrac{\partial p}{\partial T}\Bigg{)}_V= \dfrac{R}{V-b} Substituting that into my desired equation I get c_p - c_v = \Bigg{[}T\Bigg{(}\dfrac{R}{V-b}\Bigg{)}\Bigg{]}\Bigg{(}\dfrac{\partial V}{\partial...
  12. patrickmoloney

    Relation between heat capacities and van der Waals equation

    Homework Statement Find the expression for c_p - c_v for a van-der-waals gas, with the equation of state \Bigg{(}p+\dfrac{a}{V^2}\Bigg{)}(V-b)=RT Homework EquationsThe Attempt at a Solution Basically I've proved c_p - c_v = \Bigg{[} p + \Bigg{(}\dfrac{\partial E}{\partial V}\Bigg{)}_T...
  13. patrickmoloney

    Molar latent heat of phosphine

    Homework Statement [/B] Phospine exist in three forms. known as the \alpha, \beta and \gamma forms. The \alpha and \beta forms are in equilibrium with each other at 49.43 \, K, and the \alpha and \gamma forms are in equilibrium at 30.29 \, K. Obtain the molar heat of transformation for the...
  14. patrickmoloney

    Show that the entropy is non-negative

    Yeah I thought so! Thanks a lot.
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