From the equation PV = nRT ,Since temperature is constant PV = constantP1V1 = P2V2P1= pressure of gas cylinder (initial pressure)V1= volume of cylinder (initial volume)= 8 LtrP1= final pressure = 1 atmP1= final volume= (2N + 8) LtrWhere N = no of balloons filledFinal volume will be (2N+8) Ltr because cylinder will also occupied by the same gas {it won't become perfectly empty, some amount of gas will be left out. When pressure in cylinder drops to 1 atm, hydrgas inside the container will not come out, so 8 Ltr of gas (at 1 atm pressure) will be inside the cylinder} solve for N10x8 = 2N +8N= 36. (Maximum no of balloons that can be filled)