The correct option is
C 20 kgThe amount of oxygen added to increasew the pressure from 6 atm to 9 atm will be 20 kg.
From the gas law we know that,
PV=nRT
Since V,R and T are constant here,
⟹Pαn
Since pressure is increased by 1.5 times, hence number of moles should also increase by 1.5 times.
So, oxygen added should be equal to half the nymber of moles of nitrogen.
Number of moles of nitrogen in 35 kg =3500014=2500 moles
Hence, number of moles of oxygen =25002=1250 moles
One mole of oxygen weight =16g
⟹1250 moles of oxygen weight =1250×16=20000g=20kg
Hence the amount of oxygen added to increase the pressure from 6 atm to 9 atm will be 20kg.