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Homework Help: Physical chemistry problem

  1. Nov 11, 2007 #1
    1. The problem statement, all variables and given/known data
    In a closed system shown in the Figure below (http://i18.tinypic.com/7x1r8mo.jpg"), the piston is freely moving without friction and the system is initially filled with gaseous molecules A only. The mass of a piston is 100 g, its area is 10 cm2 and it is 10 cm from the bottom in the initial state of equilibrium. The pressure outside the system is 1 atm; temperature inside the system is 900 ÂșC.

    a) Calculate the initial number of molecules in the system;
    b) Write the equation describing the initial rate of decrease in the number of gaseous
    molecules if it is known that molecules A stick to the surface of the piston upon
    collision with it (molecules do not stick to any other surfaces; the processes when
    gaseous molecules react with a hot substrate surface are the basis of the chemical
    vapour deposition technology). Obtain numerical value of the initial rate.

    2. Relevant equations

    3. The attempt at a solution

    I'm really struggling with where to start on this. I'v been handed a large physical chemistry book and basically been left to my own devices. I understand the problem relates to molecular theory of gasses but could you please steer me in the right direction.
    Last edited by a moderator: Apr 23, 2017
  2. jcsd
  3. Nov 12, 2007 #2


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    Science Advisor
    Homework Helper
    Gold Member

    You can start by determining the pressure exerted by the piston on the confined "Molecules A, 900 C". The external pressure is 1 atm but the piston has mass as well.
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