This question is about determining the percentage composition by volume of a mixture of three gases, oxygen, carbon dioxide and argon in air.
Two experiments are done to determine the percentage composition by volume of oxygen.
In experiment 1, a student connects a gas syringe to a conical flask filled with iron filings. The diagram shows the apparatus the student uses.
i)
Give two changes the student needs to make to the apparatus in experiment 1 to find the percentage by volume of oxygen in a sample of air.
(2)
In experiment 2, two 100 cm3 gas syringes are connected to a reaction tube containing copper powder. The sample of air is passed over hot copper oxide. The diagram shows the apparatus that is used.
ii)
Explain why both syringes should not be filled with 100 cm3 of oxygen.
(2)