An isomer is a compound that differs by another based on either the molecular connectivity or how the atoms are connected to each other in the compound, or by stereochemistry usually.
I believe there are total number of 5 isomers for the compound of C6H14. Hexane.
Using P1V1/T1 = P2V2/T2, 1 being the conditions initially and 2 being the secondary conditions…. always make sure you convert you units first , L=695.8262L