(i) For the same amount of gas being effusedr2​r1​​=t1​t2​​⇒M2​​=p2​p1​​M1​M2​​​⇒3857​=1.60.8​28M2​​​=252 g mol−1​Also, one molecule of unknown xenon-fluoride contain only one Xe atom [M(Xe)=131], formula of the unknown gas can be considered to be XeFn​ ⇒131+19n=252;n=6.3, hence the unknown gas is XeF6​.(ii) For a fixed amount and volume, p∝T⇒1.11​⇒T⇒t⇒ Volume ​=T+10T​ where, T= Kelvin temperature =100 K=t+273=−173∘C=pnRT​=(12012​)×10.082×100​=0.82 L​