Question

How do you solve ideal gas law problems?

Answer 1

Ideal gas law problems can be solved by knowing the equation correctly. All the terms have to be understood properly. Units have to be taken special care while solving these problems. It has to be noted ideal gas law is only applied to ideal gases. Real gases follow Van der Waals equation of state.

Complete answer:
We are quite familiar with the ideal gas equation,
$PV = nRT$
Another form of ideal gas equation,
$PM = dRT$
$P = pressure\,in\,atm\,or\,bar\,N{m^{ - 2}}\,or\,Pa\,or\,bar$
$V = volume\,in\,L\,or\,d{m^{ - 3}}$
$n = no.\,of\,moles\,of\,the\,gas = \frac{{given\,mass\,of\,the\,gas(m)}}{{Molecular\,mass\,of\,the\,gas(M)}}$
$R = 8.314J\,{K^{ - 1\,}}mo{l^{ - 1}}$ (universal gas constant)
$T = temperature\,in\,K$
$M =$molecular mass of the gas in Kg
$d =$density of the gas in $Kg{L^{ - 1}}$
We should be very careful while solving ideal gas law problems. The universal gas law constant R has different values for different units.
In S.I. units, the pressure is measured in Pascals, V is measured in ${m^{ - 3}}$, n is measured in moles and T is measured in Kelvin, universal gas constant R has values of $8.314\,J\,{K^{ - 1}}\,mo{l^{ - 1\,}}\,or\,2\,cal{K^{ - 1}}mo{l^{ - 1\,}}or\,0.0821\,L\,atm\,{K^{ - 1}}mo{l^{ - 1}}$

Additional information: Ideal gas law can’t be applied to real gases. The other form of the ideal gas is also useful as it relates pressure, density and temperature in a unique sense independent of the quantity of the gas.

Note: This law makes no comment as to whether a real gas heats or cools during compression or expansion. An ideal gas undergoes no change in temperature on heating or cooling but real gases undergo a change in accordance with the Joule-Thomson effect.