A flask with a sample of gas at room temperature and pressure weighs 97.4842 g.

Question

A flask with a sample of gas at room temperature and pressure weighs 97.4842 g. The same flask with air (density = 1.17 g/L) weighs 96.8848 g. The same flask filled with water (d = 0.998 g/mL) weighs 345.86 g. The pressure in the room is 0.989 atm and the temperature is 22.2 °C.

1. Calculate the volume of the flask.

2. Calculate the mass of the air that the flask can hold.

3. Calculate the mass of the empty (no air) flask.

4. Calculate the mass of the gas in the flask.

5. Use the Ideal gas law to calculate the moles of gas in the flask.

6. Calculate the molar mass of the gas in the flask.

Explanation / Answer

1. Calculate the volume of the flask.

mass of water = (Flask + water) - (Flask + Air ) = 345.86-96.8848 = 248.9752 g of water inside

V = mass/Density = 248.9752 / (0.998) = 249.474 mL

b)

mass of air for flask:

P V= nRT

n = PV/(RT)

T = absolute. V = in liters, R =? 0.082 Latm/molK and P = atm

n = (0.989)(249.474/!000) /(0.082*(22.2+273))

n = 0.0101927 mol of aig

mass = mol*MW =0.0101927*29 = 0.2955883 g = 295.5 mg of air

3. Calculate the mass of the empty (no air) flask.

Mass of flask = 96.8848-0.2955883 = 96.5892 g of flask

4. Calculate the mass of the gas in the flask.

Mass of gas = (Mass of flas + Air) - (air) = 97.4842 -96.5892 = 0.895 g of gas

5. Use the Ideal gas law to calculate the moles of gas in the flask.

PV = nRT

n = PV/(RT)

n = (0.989)(249.474 /1000) /(0.082*(22.2+273)) = 0.010192 moles of gas

6. Calculate the molar mass of the gas in the flask.

Molar Mass = mass/ mol

mol = 0.010192

mass = 0.895 /0.010192

mass of gas = 87.81 g

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