Question

A balloon vendor at a street fair is using a tank of helium to fill her balloons. The tank has a volume of 149.0 L and a pressure of 121.0 atm at 19°C. After awhile she notices that the valve has not been closed properly. The pressure had dropped to 106.0 atm. How many moles of gas have been lost?
_____ moles

Answer 1

1st find initial moles of gas present:

we have:

P = 121.0 atm

V = 149.0 L

T = 19.0 oC

= (19.0+273) K

= 292 K

find number of moles using:

P * V = n*R*T

121 atm * 149 L = n * 0.08206 atm.L/mol.K * 292 K

n = 752.4 mol

Since volume and temperature here is constant

Lets calculate the final mol of gas in container

we have:

n1 = 752.4 mol

P1 = 121.0 atm

P2 = 106.0 atm

we have below equation to be used:

P1/n1 = P2/n2

121.0 atm / 752.4 mol = 106.0 atm / n2

n2 = 659.1 mol

so,

moles escaped = n1 - n2

= 752.4 mol - 659.1 mol

= 93.3 mol

Answer: 93.3 mol