Hello Aspirant,

P(1)*V(1)/T=P(2)*V(2)/T

20*1=P(2)*50

P(2)=0.4 atm

This formula is valid since the no. of moles did not change and is derived from Ideal gas equation PV=nRT

ideal gas law, also called the general gas equation, is the equation of state of a hypothetical ideal gas. It is a good approximation of the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of the empirical Boyle's law, Charles's law, Avogadro's law, and Gay-Lussac's law.