Question

You have a 30.0L cylinder of helium at a pressure of 132 atm and a temperature of 19 Celcius. The Hlium is used to fill a balloons to a volum of 1.80L at 145mmHg and 27 Celcius.

How many baloons can be filled with He? (Assume that the cylinder can provide He until its internal pressure reaches 1.00 atm. i.e., there are 131 atmospheres of usable He in the cylinder) Show all your work with units.

Please help. Thank you so much!

Answer 1

Calculation of Number of moles of He gas in the cylinder:

We know that PV = nRT

Where

P = pressure = 132 atm

V = volume = 30.0L

n = number of moles = ?

R = gas constant = 0.0821 Latm/(mol-K)

T = temperature = 19 oC = 19+273 = 292 K

Plug the values we have n = PV / RT

                                      = 165.2 moles

Calculation of Number of moles of He gas in the ballon :

We know that P'V' = n'RT'

Where

P' = pressure = 145 mm Hg = 145/ 760 atm = 0.19 atm                    Since 1 atm = 760 mm Hg

V' = volume = 1.80L

n' = number of moles = ?

R = gas constant = 0.0821 Latm/(mol-K)

T' = temperature = 27 oC = 27+273 = 300 K

Plug the values we have n' = P'V' / RT'

                                      = 0.014 moles

So number of baloons is = n / n'

                                    = 165.2 / 0.014

                                     = 11848