Molecular Masses of Gaseous Substances

Determining the Molecular Mass of Oxygen. Assemble a setup for determining the molecular mass of oxygen (Fig. 34) and check its tightness by parts. 

Checking the Clamp. Fill the siphon with water. It must contain no air bubbles. To do this, take the test tube off stopper 1, open clamp 3, blow air through the tube with stopper 1, and close the clamp again. See if any water flows out of the siphon tube. 

Checking the Test Tube and the Setup as a Whole. Connect the test tube to the setup, lower the end of the tubing into the beaker with 

Lower the end of the tubing into the beaker with water, close the clamp, and return the setup to its previous position. Fill flask 2 with water up to its neck (the volume of the flask should be one litre). Pour about 2 g of potassium chlorate into the refractory test tube of the setup so that no crystal.s remain in the upper part of the tube. 

Determine the mass of the test tube with the potassium chlorate approximately on a technical chemical balance, and then weigh it on an analytical balance with an accuracy up to 0.01 g. Carefully connect the test tube to the setup. Check the tightness of the latter again. 

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