Molecular Weight of a Gas

Purpose:

You will be collecting one of the following gases by displacement of either air or water.

Materials:

• Get the chemicals needed for the gas you are going to produce.
  1. Oxygen gas--4 grams of 33% manganese dioxide and 67% potassium chlorate by mass.
  2. Hydrogen gas--zinc metal and sulfuric acid.
  3. Carbon dioxide gas--20 grams of calcium carbonate and hydrochloric acid.
• Testube with a one hole stopper and glass rod bent to shape.
• Collecting bottle with a stopper.
• barometer
• balance or scale

Procedure:

1. Take your stoppered bottle and immediately weigh it with air.
2. Record the barometric pressure and temperature of the air.
3. Fill the bottle with water up to the bottom of the stopper and then measure the amount of water (this is the amount of gas the bottle holds).
4. See the diagram below for connecting up the testube to the bottle.
5. Mix the chemicals in the testube and immediately stopper securely.
6. Let some of the gas produced run out of the tubing before placing into the collecting bottle.
7. Fill your bottle with gas and then stopper.
8. If the bottle and stopper are wet, dry them carefully so the stopper does not come out.

   

   
   

Data Table:

mass of bottle and stopper with air_________________

mass of bottle and stopper with gas_________________

temperature of gas_____________

barometer reading______________

volume of bottle to stopper (water vol.)____________

mass of assembly_______________

volume of gas corrected to STP_______________

molecular weight of gas (experimental)_______________

molecular weight of gas (accepted)___________________

percent error_______________

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