Question

A vessel of volume 5L contains 1.4g of nitrogen at a temperature 1800K .The pressure of the gas if 30% of its molecules are dissociated into atoms at this temperature is

Answer 1

Since some of the nitrogen gas is dissociated into atoms, the vessel will now contains a mixture of molecular nitrogen and atomic nitrogen. Let us assume the partial pressure of ​molecular nitrogen and atomic nitrogen be equal to p1 and p2, respectively.

Hence,

mass of molecular nitrogen, m1 = 1.4×70/100=0.98 g

mass of atomic nitrogen, m2 = 1.4 - 0.98 = 0.42g

According to Dalton's law, Total pressure P = p1 + p2

P=p1+p2=n1RT/V+n2RT/V
=(0.98/28×0.0821×1800/5)+(0.42/14×0.0821×1800/5)
P = 1.0344 + 0.887 = 1.9214 atm