Tiêu đề EDX Topic 8 gases in the atmosphere.pdf ✅

Topic 9 2 Composition of Air Composition of Air Clean dry air is a mixture of gases. (78% Nitrogen, 21% Oxygen, 0.9% Argon, 0.04% Carbon Dioxide & 0.06% other gases) Separation of Oxygen & Nitrogen from Air Air is cooled down & liquefied Fractional Distillation of Liquid Air Example 1 Experiment to determine % of Oxygen in Air Fill a gas syringe with 100cm3 of air Copper in the glass tube is heated using a bunsen burner Push the plunger of the syringe to force air to pass over copper powder, oxygen reacts with copper forming Copper Oxide and colour changes from reddish brown into black Keep pushing air back and forth between the 2 syringes until volume of air stays constant Stop heating and allow the apparatus to cool. Then push all the gas into one syringe and measure its volume. Volume of Oxygen = Total Volume of Air at the start - Volume of Air at the end Percentage of Oxygen = (Volume of Oxygen / Total Volume in Air) x 100
3 Example 2 Experiment to determine % of Oxygen in Air Place a damp iron wool in a measuring cylinder Invert the measuring cylinder into a trough containing water Measure the starting volume of air in the measuring cylinder Leave the apparatus for a week, the water will rise up the measuring cylinder (to replace the oxygen used up in the reaction with iron) Measure the final volume of air in the measuring cylinder Percentage of Oxygen = (Volume of Oxygen / Total Volume in Air) x 100 Topic 9