1.A helium-filled weather balloon has a volume of 811 L at 23 °C and 750 mm Hg.

Question

1.A helium-filled weather balloon has a volume of 811 L at 23 °C and 750 mm Hg. It is released and rises to an altitude of 8.69 km, where the pressure is 281 mm Hg and the temperature is -34 °C. The volume of the balloon at this altitude is ______ L.

2.

A sample of hydrogen gas occupies a volume of 9.89 L at 44 °C and 0.944 atm.

If it is desired to decrease the volume of the gas sample to 8.88 L, while increasing its pressure to 1.29 atm, the temperature of the gas sample at the new volume and pressure must be_______ °C.

3.A sample of hydrogen gas collected at a pressure of 1.11 atm and a temperature of 16.0°C is found to occupy a volume of 29.9 liters. How many moles of H2 gas are in the sample?_____ mol

4.A sample of argon gas collected at a pressure of 0.836 atm and a temperature of 281 K is found to occupy a volume of 604 milliliters. How many moles of Ar gas are in the sample? _____mol

Explanation / Answer

1) PV= nRT

n of He= (750mmHg/760mmHg x 1atm) x 811L/0.082L.atm/mol.K x 296K = 32.97 mol

the moles of gas at beginning are the same as the moles at the end.

V= 32.97 mol x 0.082L.atm/mol.K x 239 K/(281mmHg/760mmHg x 1atm) = 1747.6 L

2) mol H2= 0.944atm x 9.89L/0.082L.atm/mol.K x 317K= 0.359 mol

Final T:

T= 1.29atm x 8.88L/0.359 mol x 0.082L.atm/mol.K= 389K

3) moles H2= 1.11atm x 29.9L/0.082L.atm/mol.K x 289K= 1.4 mol

4) moles Ar= 0.836atm x 0.604L/0.082L.atm/mol.K x 281K= 0.022 mol

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