Question
Sun December 25, 2011 By: Sai-netra Ramesh

sir, if PV=nRT, P?T and if you see it with respect to V, V?T. but since p?1/V, there is a doubt on which relation to follow because both give opposite results on either increase or decrease of T... so what should we do???

Expert Reply
Mon December 26, 2011

According to Avogadro's law V/n = k
According to Boyle's law PV = k
Charles's Law compares volume and temperature i.e. V/T = k
Now on combining all these we have PV/nT = k
When replace k with the universal gas constant R
Thus, PV/nT = R
Its not that you have to apply only one relation, all the laws have to be applied.

Now if we consider increase of temperature then Pressure would also increase and similarly volume would also increase now since both volume and pressure can’t increase at the same time. So this law has various consequences:

  1. If temperature and pressure are kept constant, then the volume of the gas is directly proportional to the number of molecules of gas.
  2. If the temperature and volume remain constant, then the pressure of the gas changes is directly proportional to the number of molecules of gas present.
  3. If the number of gas molecules and the temperature remain constant, then the pressure is inversely proportional to the volume.
  4. If the temperature changes and the number of gas molecules are kept constant, then either pressure or volume (or both) will change in direct proportion to the temperature.
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