The density of a pure liquid at 25 degrees Celsius was calculated by determining the mass and volume of a sample of the liquid.
A student measured the mass of a clean, dry 25.00 mL volumetric flask, filled the flask to its calibration mark with the liquid, and then measured the mass of the flask and liquid. The recorded measurements are shown in the table above. On the basis of this information, to how many significant figures should the density of the liquid be reported?
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Answer : The partial pressure of helium is,
Solution : Given,
Molar mass of = 32 g/mole
Molar mass of helium = 4 g/mole
Molar mass of = 28 g/mole
Total pressure of gas =
As we are given gases in percent, that means 10 g of oxygen gas, 50 g of helium gas and 40 g of nitrogen gas present in 100 g of mixture.
First we have to calculate the moles of oxygen, helium and nitrogen gas.
Now we have to calculate the total number of moles of gas mixture.
Now we have to calculate the moles fraction of helium gas.
Now we have to calculate the partial pressure of helium.
where,
= partial pressure of helium
= total pressure
= mole fraction of helium
Now put all the given values in this formula, we get
Therefore, the partial pressure of helium is,