Question

05 Question (1 point) See page 289 Aballoon vendor at a street fair is using a tank of helium to fill her balloons. The tank has a volume of 191.0L and a pressure of 128.0 atm at 25.0°C After a while she notices that the valve has not been closed properly. The pressure had dropped to 118.0 atm. (The tank is still at 25.0°C) 1st attempt W See Periodic Table See Hint How many moles of gas has she lost? mol

Answer 1

This question is based on the Ideal gas equation.

ideal gas equation is PV= nRT.

where P is pressure of gas.

V is volume

n is number of moles of gas

R is gas constant.

and T is the temperature.

at initial stage (before lossing gas) let the pressure is P1, volume is V1 and temperature is T1 calculate the number of moles of gas at this condition:-

n=PV/RT

n= (128atm×191L)÷(0.0821atmL/mol.K ×298K)

n= 999.27moles.

Again using P1V1=n1RT1 before losing gas.

And. P2V1=n2RT1 after losing gas.

As the volume, gas constant and the temperature remains constant.

Dividing these 2 equations, we get a relationship:-

P1/P2=n1/n2

128atm/118atm=999.27moles/n2

1.08 = 999.27moles/n2

n2=999.27moles/1.08

n2= 925.25 moles

Thus the number of moles before losing=999.27 moles

Number of moles after losing gas= 925.25 moles

Number of gas moles she lost = 999.27-925.25

Number of moles she lost = 74.02 moles

hence the answer is 74.02 moles.