A cylinder contains hydrogen gas at 20 atm. How many balloons of 500 ml capacity can be filled up completely from the gas cylinder at the external atmospheric pressure of 640 mm of Hg at constant temperature? The volume of empty cylinder is 20 liters.​

950 balloons

Explanation:

P1 = pressure inside cylinder = 20atm

P2 = pressure outside = 640mmhg = 0.842105 atm

V1= volume of cylinder =20L = 20,000 ml

V2 = volume of a single balloon= 500ml

n = number of balloons

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

- lead + phosphoric acid = hydrogen + lead(ii) phosphate