Oxygen and Oxides Flashcards
What are the gases present in air and their approximate percentage?
Nitrogen - 78%
Oxygen - 21%
Argon - 0.96%
Carbon dioxide - 0.04%
Explain experiments to investigate the percentage by volume of oxygen in air
Copper: 100cm3 of air is in a gas syringe. As heat is applied to a silica tube packed with copper, this syringe is pushed backwards and forwards. Copper turns black as copper oxide is formed.
Busen is moved along the tube so that it is always heating fresh copper. The volume stops contracting and the copper stops turning black once all the oxygen has been used up. 79cm3 of gas is left.
Iron: Sprinkle iron filings into a wet tube, they will stick to the sides. The tube is inverted in a beaker of water and the level of water in the tube is marked by a small rubber band. The tube is now left for a week for the iron to use up all the oxygen. Water level rises and new level is marked using rubber band.
Describe the laboratory preparation of oxygen
Heat a solution of hydrogen peroxide and solid manganese oxide. Oxygen collects in an inverted test tube in a beaker of water.
Describe the reactions of magnesium, carbon and sulfur with oxygen in air
Magnesium: burns with a bright white flame to give a white ash of magnesium oxide.
Sulfur: burns with a bring blue flame
Carbon: carbon dioxide produced and a small yellow-orange flame and sparks.
Describe the laboratory preparation of carbon dioxide
Place calcium carbonate in a conical flask. Add hydrochloric acid in the conical flask and carbon dioxide will be released. Use downwards displacement to measure how much CO2 was made.
Calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide
Describe the formation of carbon dioxide
Put some copper(II) carbonate into a test tube and insert a bung with a delivery tube at the top
- Clamp the test tube at a 90º angle and insert the delivery tube into another test tube
- Heat the copper(II) carbonate with a bunsen burner.
- Carbon dioxide produced
Describe the properties of carbon dioxide
Carbon dioxide is more dense than air (which is why it can be collected using the downward delivery method). It is also soluble in water at high pressure.
Explain the use of carbon dioxide
Used in carbonated drinks because it dissolved in water under pressure.
Used in fire extinguisher because the dense gas sinks onto the flames to prevent any oxygen from reaching them.
What are the dangers of carbon dioxide?
Carbon dioxide absorbs longer-wave radiation and re-emits it back down to the earth. This prevents heat from escaping the atmosphere, which will rise the temperatures on earth, this leads to global warming so glaciers melt.
