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Math Help - Thermodynamics (Ideal gases)

  1. #1
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    Thermodynamics (Ideal gases)

    I tried posting this in physicshelpforum but it says my account doesn't have sufficient privilages or is disabled by admin.

    So i'm posting it here.
    ---------------------------------------------------------------------
    Please find the question in the attachment.I need to get it solved by tonight,please try to respond ASAP.Any help is much appreciated.
    Thank you
    Attached Thumbnails Attached Thumbnails Thermodynamics (Ideal gases)-img00350-20100528-1846.jpg  
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  2. #2
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    You have to use the equation of state for an ideal gas: PV=nRT. Once you find the pressure in part (a), for part (c) use

    \frac{PV}{T}=nR

    Assuming that no air escapes during the compression so that nR remains constant. Hence set the initial value of the LHS equal to the final value:

    \frac{P_iV_i}{T_i}=\frac{P_fV_f}{T_f}

    And from what I understood the pressure remains constant so you have:

    \frac{V_i}{T_i}=\frac{V_f}{T_f}

    Now plug in the values and solve for V_f. By the way, you have to convert your tempratures from Celcius to Kelvins.
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  3. #3
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    I got that part, but can you explain how to determine pressure (first part of question) given the mass 10KG. You suggested using PV=nRT but we don't know n and new Volume of the gas.
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  4. #4
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    Quote Originally Posted by kandyfloss View Post
    I tried posting this in physicshelpforum but it says my account doesn't have sufficient privilages or is disabled by admin.

    So i'm posting it here.
    ---------------------------------------------------------------------
    Please find the question in the attachment.I need to get it solved by tonight,please try to respond ASAP.Any help is much appreciated.
    Thank you
    For part (1) , Use the fact that P=\frac{F}{A}=\frac{mg}{V/d}

    (2) Use the ideal gas equation , pV=\frac{N}{N_A}RT and solve for N

    (3) this is a Charles' law case .
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  5. #5
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    The volume of the cylinder is 0.050 m^3 and the height of cylinder is not given.Only the final position of the piston is given ,its not the full height of the cylinder.
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