Gases In The Atmosphere Flashcards
What are the four most abundant gases in the air including their percentages
Nitrogen 78%, oxygen 21%, argon 0.96%, carbon dioxide 0.04%
How do you set up the bell jar experiment to find out how phosphorus burns in the air
Mark initial water level on bell jar, light the phosphorus, seal bell jar with bung, allow phosphorus to burn, mark final water level on bell jar with
What happens when phosphorus is set alight
It creates a bright yellow flame, white smoke and water rises up in bell jar
Why does the water rise in the belll jar experiment
The phosphorus reacts with oxygen in the air so the water rises to replace the oxygen
How much does the water rise by
About 20% as it has used up all the oxygen in the air which is 21%
What is the word and symbol equation for the phosphorus oxygen reaction
Phosphorus + oxygen —> phosphorus oxide
4P(s) + 5O2(g) —> P4O10 (s)
How is copper used to determine the volume of oxygen in the air
An excess of powdered copper is put into a glass tube attached to two gas syringes. The tube is then heated. At the beginning of the experiment one gas syringes has 0cm3 of air in it, the other has 100cm3. The air in the syringes us passed over the copper while it is heated
What are the results of copper being used to determine the volume of oxygen in the air
In each pass over the copper the volume of air in the tube will decrease finishing at about 79cm3
What is the word and symbol equation for copper and oxygen reacting
Copper + oxygen —> copper(2) oxide
2Cu(s) + O2 (g) —> 2CuO(s)
What colour change occurs in the copper
It changes from pink-brown to black as copper oxide is formed
How can we use iron to determine the volume of oxygen in the air
Place wet iron fillings in the base of a conical flask, using a connecting tube connect it to a gas syringe. Record the initial volume of air in the gas syringe and in the connecting tube and the conical flask. Leave experiment for about a week until the readings on the gas syringe stop changing, record final reading on gas syringe
How do you calculate the volume of oxygen used up
Calculate the total volume of air by adding the volume of air in the conical flask, the volume of air in the connecting tube and the initial reading on the gas syringe. Then calculate the total volume of air at the experiment by adding up the same stuff but instead with the final volume of air in the gas syringe. Subtract the second value from the first value. Divide your answer by the total volume of air at the start of the experiment then x100.
Why are iron fillings used in the rusting of iron experiment
We can assume that the small volume occupied by the iron fillings is negligible
What are two reasons why your volume of oxygen calculated may be less than 21%
The experiment was not set up for long enough so the iron has not had long enough to react with all the oxygen in the apparatus. Not enough iron was adding in the beginning as it must be in excess so there is enough iron to react with all the oxygen present
What happens when magnesium combusts with oxygen. Symbol equation
Magnesium burns with a bright white flame creating a white powder of magnesium oxide
2Mg(s)+ O2(g) —> 2MgO(s)
What happens when sulfur combusts in oxygen. Symbol equation
Sulfur produces a blue flame when burned in oxygen. Poisonous, colourless sulfur dioxide gas is produced. S(s) + O2(g) —> SO2(g)
What happens when hydrogen combusts in oxygen. Symbol equation
Hydrogen produces a pale blue flame when burned in oxygen. The product is water
2H2(g) + O2(g) —> 2H2O(l)
What happens when magnesium oxide is dissolved in water. Symbol equation
MgO(s) + H2O(l) —> Mg(OH)2(aq). The white powder formed is not very soluble but a very small amount does dissolve to form a alkaline solution
What happens when sulfur dioxide is dissolved in water. Symbol equation
Sulfur dioxide dissolves in water to form an acidic solution called sulfurous acid.
SO2(g)+H2O(l)—> H2SO3(aq)
How is carbon dioxide formed from the thermal decomposition of metal carbonates
When metal carbonates are heated strongly they split to give the metal oxide and carbon dioxide. This is an example of thermal decomposition
What is an example of thermal decomposition
Copper (2) carbonate which is a green powder decomposes when heated to produce black copper (2) oxide. CuCO3(s) —> CuO(s) + CO2(g)
How is thermal decomposition used commercially
Calcium carbonate doesn’t compose unless it is heated at quite high temperatures. It is used to convert limestone (calcium carbonate) into quicklime (calcium oxide)
What is carbon dioxide
A greenhouse gas
How can increasing amounts of carbon dioxide in the atmosphere affect climate change
The greenhouse effect occurs when high-energy UV and visible light from the sun pass through the atmosphere and warm up the surface of the earth. The surface of the earth radiates infrared radiation. The IR radiation is absorbed my molecules such as CO2 in the atmosphere which then give out energy in all directions heating the atmosphere
