A party-supply store sells a helium-gas cylinder with a volume of 1.55 × 10^-2 m^3. If the cylinder provides 1.81 m^3 of helium for balloon inflation (at STP), what must be the pressure inside the cylinder?

Question

Now I don't understand this at all. My book does not explain how to do problems like these and I need help. Any takers?

Answer 1

In essence you will place the same number of mols that occupy 1.81 m^3 into a volume of 0.0155 m^3 so the pressure will increase by the inverse of the volumes; i.e.,
1 atm (the initial P) x (1.81/0.0155) = ? atm