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.

Answer 1

Mass of water= mass of flask with water - Mass of flask with air

=(345.86-96.8848)g

=248.9752g.

1.Volume of flask=volume of water=Mass of water/density of water

=248.9752/0.998

249.4741mL.

2.mass of air=0.249.4741×1.17g

   =0.2918g.

3.mass of flask=Mass of flask with air -Mass of air

   =96.8848-0.2911

=96.5929g

4.mass of gas in flask=mass of flask with gas -mass of epy flask

   =97.482-96.5929

   =0.8891g

5.Pv=nRT

   n=Pv/RT=0989×249.4741/82.1×295.2

   =0.0101mol

6.n=mass/molar mass

Molar mass=0.8891/0.0101

   =87.33g/mol.