[chloe chan]

1.A sample of neon occupies 105 liters at 27 degree celcius under a pressure of 985 torr.What volume would it occupy at standard temperature and pressure?
2.What pressure,in atm,is exerted by 54.0grams of Xe in a 1.00 liter flask at 20 degress celcius?
3.A helium-filled weather balloon has a volume 0f 2.05*10^5 L.How many grams of helium would be required to inflate this balloon to a pressure of 745 torr at 21 degree celcius?
4.Nitric acid,a very important industrial chemical,is made by dissolving the gas nitrogen dioxide,NO2,in water.Calculate the density of NO2 gas,in g/L,which occupies 1.00L at 1.24 atm and 50 degree celcius.
5.a)A 120ml flask contained 0.345 gram of gaseous compound at 100 degree celcius and 1.00 atm pressure.What is the molecular weight of the compound?
  b)Additional analysis of the gaseous compound in 5a showed that it contained 54.5% carbon,9.10% hydrogen and 36.4% oxygen by mass.What is its molecular formula?
6.Calculate the mole fraction of oxygen when 200 torr of air(760 torr total) is oxygen.                                                  

[opti384]

First show your attempts.

[chloe chan]

1.105L-> 27 oC
     ?L -> 0 oC(STP)

105*27=2835L

Is it correct?

[chloe chan]

6.Vrms=square root of 3(8.314)(273.15+25) / 0.002
         =1928.27(don't know the unit)

is this correct?

[opti384]

For the first question, think how you can use the ideal gas equation.

[chloe chan]

but ideal gas equation is PV=nRT,i dont think can use this formula.how about P1V1/T1=P2V2/T2,where P1 is 985torr,V1=105L,T1=300.15K(27+273.15);P2=760torr,V2=? and T2=273.15

I substitute all the values into the formula,and get V2=123.84L.

[opti384]

Of course you are right. After all, P1V1/T1=P2V2/T2 is from the ideal gas equation.

[Borek]

but ideal gas equation is PV=nRT,i dont think can use this formula.how about P1V1/T1=P2V2/T2

P₁V₁ = nRT₁

P₂V₂ = nRT₂

If it is the same sample of gas, n is identical. R is constant by definition, so

nR = P₁V₁/T₁

nR = P₂V₂/T₂

and

P₁V₁/T₁ = P₂V₂/T₂

[chloe chan]

Of course you are right. After all, P1V1/T1=P2V2/T2 is from the ideal gas equation.

ok.i never know the equation is derived from the ideal equation.thanks to let me know!

[chloe chan]

but ideal gas equation is PV=nRT,i dont think can use this formula.how about P1V1/T1=P2V2/T2

P₁V₁ = nRT₁

P₂V₂ = nRT₂

If it is the same sample of gas, n is identical. R is constant by definition, so

nR = P₁V₁/T₁

nR = P₂V₂/T₂

and

P₁V₁/T₁ = P₂V₂/T₂

thanks your explanation!