1) A compressed gas cylinder contains 1.00 103 g of argon gas. The pressure inside the cylinder is 1903 psi (pounds per square inch) at a temperature of 13°C. How much gas remains in the cylinder if the pressure is decreased to 574 psi at a temperature of 28°C?
2)A student adds 2.00 g of dry ice (solid CO2) to an empty balloon. What will be the volume of the balloon at STP after all the dry ice sublimes (converts to gaseous CO2)?
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3 Answers

1) A compressed gas cylinder contains 1.00 103 g of argon gas. The pressure inside the cylinder is 1903 psi (pounds per square inch) at a temperature of 13°C. How much gas remains in the cylinder if the pressure is decreased to 574 psi at a temperature of 28°C?
You'll need to assume that the Ideal Gas Law applies:
PV=nRT
where P=pressure, V=volume, n=number of moles of gas, T = absolute temperature, and R=Universal Gas Constant 0.08205 litatm/molK
First find the volume of the cylinder using the initial conditionsL
V= nRT/P
= (1.00x10^3g/39.9g/mol Ar)*(0.08205 litatm/molK)*(13 + 273.16 K)/(1903psi/(14.7psi/atm))
= 4.546 lit
Now calculate the new amount of moles needed to meet the new conditions:
n=PV/RT
= (574psi/14.7psi/atm)*(4.546lit)/[(0.08205litatm/molK)*(28+273.16K)]
= 7.184 moles = 7.184 moles * (39.9 g/mol Ar) = 287g Argon left.
2)A student adds 2.00 g of dry ice (solid CO2) to an empty balloon. What will be the volume of the balloon at STP after all the dry ice sublimes (converts to gaseous CO2)?
Use PV=nRT to solve for V:
V = nRT/P
= (2.00g/(44g/mol CO2))*(0.08205litatm/moleK)*(273.16K)/(1 atm)
= 1.02 liters of CO2
Hope this helps

I'm guessing... The gas can't escape the cylinder, so it all the gas will remain in the cylinder; 100g of Argon gas. But that seems a bit too easy... They don't say anything about the volume...

complicated point. lookup from google or bing. this will help!