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Chemistry help needed....

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I'm posting this in case anyone one here can help a student I'm working with (obviously I'm NOT working with her in chemistry:D) She's absolutely stuck on these two homework problems and can't get ahold of her teacher.


1. The total mass that can be lifted by a baloon is equal to the difference between the mass of gas in the balloon and the mass of air displaced by the balloon.

*How much mass could be lifted by the balloon?

**How much mass could the same balloon lift it it was filled with helium at the same pressure and temperature?


2. Use the barometric formula P=P0e=-Mgh/RT to estimate the height to which the balloon with a payload of 1000kg can rise when filled with hydrogen. (The balloon will rise until the density equals that of the surrounding air.) Assume that the temperature fo the air does not change with altitude. Use the average molar mass M (in kg) for air based on 80% N2, 20% O2, and use 9.81 m s-2 (Hint: first reassure yourself that the mass of displaced air inside the balloon is proportional to the atmospheric pressure)


So, anyone up for the challenge this late at night?

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Is there any further information given? You can derive the formula for the mass to be lifted via Sum of Forces = ma. The difference in mass is equal to V(Rho of air - Rho of He). Based on what you have posted, I don't see how to get rid of the volume in that formula.

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