KCET 2020 Chemistry Solved Paper

Since temperature and pressure is constant, we can assume it to be in STP condition.
Now, let the total volume be 100 L
Moles of He present =

25

22.4

=1.12mol
Mass of He present =1.12×4=4.48g
Moles of CH4 present =

75

22.4

=3.35mol
Mass of CH4 present =3.35×16=53.60g
Hence, the mass percentage of CH4=

53.60

58.08

×100=92.28%