2 - Gases In The Atmosphere Flashcards
What are the approximate percentages by volume of the four most abundant gases in dry air?
Nitrogen, N2 - 78.1
Oxygen, O2 - 21.0
Argon, Ar - 0.9
Carbon dioxide, CO2 - 0.04
How do you determine the volume of oxygen in the air using metals (copper)?
Method:
- take 2 Gas syringes and connect them with a capillary tube. Also need a bunsen burner.
- left syringe should have 0ml of air and the right one should have 100ml of air
- Put the bunsen burner under the capillary tubes which should be filled with excess quantity of copper turnings, this will start the reaction.
- pass the air in the syringe over the copper turnings to allow the oxygen in the air to react.
- keep passing the air over until you get a repeat reading many times
- the volume of air in the syringe should get smaller.
- remove the bunsen burner and leave for 5 minutes to cool before taking the final measurements. The air in the syringe will have expanded.
- the copper in the tube will have changed colour to black because copper + oxygen –> copper oxide
results:
- The left syringe should be at 0ml and the right should be at around 80ml
- All the oxygen in the air is therefore used up, and so the volume of the air decreases by about 20% (the percentage of oxygen in air).
How do you determine the volume of oxygen in the air using metals (iron)?
Method:
- Place wet Iron fillings at the end of a burette (use Vaseline if Iron Filings does not stick)
- Use a clamp to hold the burette vertically in the trough of Water
- Measure and note the starting height of Water level in the burette
- Leave apparatus for several days
- Measure and note the final height of Water level in the burette
results:
- As the Water level will rise to replace the volume of Oxygen lost during reaction to form Iron (II) Oxide, a constant Water level will be reached as Iron fillings will fully oxidise with Oxygen in the air
How do you determine the volume of oxygen in the air using metals (iron)?
Method:
- Add Phosphorus into an evaporating dish and place it on a trough of Water
- Ignite Phosphorus using a candle
- Cover evaporating dish with a bell jar
- Measure and note the starting height of the Water level in the bell jar
- Leave apparatus for several days
- Measure and note the final height of the Water level in the bell jar
Results:
- As the Water level will rise to replace the volume of Oxygen lost during this reaction, a constant level will be reached as Phosphorus will use up all Oxygen in Air to burn (Oxygen is one of three Elements that a fire needs)
What does combustion mean?
Chemical reaction involving burning (ignition)
describe the combustion of magnesium in oxygen:
Magnesium reacts with oxygen producing a bright white flame leaving behind a white ash of magnesium oxide.
magnesium + oxygen → magnesium oxide
2Mg (s) + O₂ (g) → 2MgO
describe the combustion of hydrogen in oxygen:
Hydrogen reacts with oxygen in an explosive reaction. This is the basis of the ‘squeak pop’ test for hydrogen in test tube. With larger quantities of hydrogen this explosion can be dangerous. It is In chemistry, something that’s exothermic.
hydrogen + oxygen → water
2H₂ (g) + O₂ (g) → 2H₂O (l)
What does Exothermic mean?
In chemistry, something that’s exothermic has to do with the release of heat
describe the combustion of sulfur in oxygen:
Sulfur reacts with oxygen producing a blue flame and a colourless gas is produced.
sulfur + oxygen → sulfur dioxide
S (s) + O₂ (g) → SO₂ (g)
What is thermal decomposition?
Breakdown of Compounds using heat energy
Describe the Formation of Carbon Dioxide from the Thermal Decomposition of Metal Carbonates. Including Copper (II) Carbonate:
Carbon Dioxide is produced when Metal Carbonates are heated through Thermal Decomposition:
Equation:
Metal Carbonate → Metal Oxide + Carbon Dioxide
Copper (II) carbonate:
- copper carbonate –> copper oxide + carbon dioxide
When Copper (II) Carbonate is Thermally Decomposed, it Turns from Green (Copper (II) Carbonate) to Black (Copper Oxide)
What is carbon dioxide?
Greenhouse gas that contributes to climate change when present in large amounts
How do greenhouse gases, like carbon dioxide, cause climate change?
- Sun emits short wave radiation (ultraviolet radiation) that enters the Earth’s atmosphere
- Earth’s surface absorbs short wave radiation from the sun and re-emits it as long wave radiation (infrared/heat)
- Greenhouse gases - such as Carbon Dioxide, absorb and re-radiate this long wave radiation, retaining heat within the atmosphere
- Earth’s average temperature rises as a result
