Annoying pressure prob. that is so easy i should not have to ask for help

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SUMMARY

The discussion centers on calculating the volume ratio of a helium-filled balloon at sea level versus at an altitude of 2530 m, where the pressure is 0.710 atm and the temperature is 5.60°C. The Ideal Gas Law is applied, specifically the equation (p1v1)/t1=(p2v2)/t2. The user initially miscalculates the pressure at sea level as 0.74667 atm and is confused about the correct ratio of pressures to use for volume comparison. The correct approach is to solve for the volume ratio v2/v1, rather than assuming volume remains constant.

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A child's helium-filled balloon escapes at sea level and 20.0°C. When it reaches an altitude of 2530 m where the temperature is 5.60°C and the pressure only 0.710 atm, what is the ratio its volume compare to that at sea level?


so i am going to use the ideal gas law... that is (p1v1)/t1=(p2v2)/t2

so if the gas is contained in a balloon, that means that the gas will still have the same amount of volume that it could fill so i am going to mulitiply v1 and v2 out so that i have

p1/t1=p2/t2

p1/293.15 K=0.710/ 278.75 K

p1=0.74667 atm

and now for the ratio...i am not sure if it is p1/p2 or p2/p1...but i think it may be p1/p2 and i get 1.05

either way i do the raito i still get the worng answer...please help me
 
Physics news on Phys.org
If you are going to assume that the volume is unchanged, then there is not much point in computing a ratio of volumes, is there? Don't assume that and solve for v2/v1.
 

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