For 1 mole of a gas, R =PV/T-. We know from Avogadro’s law that under identical condition of temperature (T) and pressure (P), the volume (V) occupied by 1 mole of all the gases is same. So, for 1 mole of all gases, the value of R is same irrespective of the condition of temperature and pressure under which the volume is measured. Thus R, the universal or molar gas constant, is universal for all gases.