A canister containing air has a volume of 8.5 L and a pressure of 1.45 atm when the temperature is 310 K. What is the pressure when the volume is increased to 18.0 L and
the temperature is reduced to 280 K?

yes the answer is total mass in unchanged   : )

5 structural isomers

the isomers are:

n-exane :   ch3ch2ch2ch2ch2ch3

2-methylpentane :   ch3ch(ch3)ch2ch2ch3

3-methylpentane :   ch3ch2ch(ch3)ch2ch3

2,3-dimethylbutane :   (ch3)2chch(ch3)2

2,2-dimethylbutane :   (ch3)3cch2ch3