Gas Chemistry Flashcards
How much % of the air is nitrogen?
About 78%
How much % of the air is oxygen?
About 21%
How much % of the air is carbon dioxide?
About 0.03-0.04%
How much % of the air is argon?
About 1%
Apart from the main gases in the air what else is the air made up of?
Small proportions of other noble gases and varying proportions of water vapour.
What is nitrogen’s physical properties, is it reactive or unreactive, why and what are its uses?
Nitrogen is a colourless and odourless gas.
It is unreactive because it has a triple covalent bond.
Nitrogen is used in food packaging, as a coolant and for reduction in ammonia.
What is the test for ammonia and what is ammonia used for?
You use a glass rod and dip it in concentrated hydrochloric acid. Then apply the rod to the gas, if ammonia is present there will be a white fumes.
Ammonia is used in the manufacturing of fertilisers by its reaction with acids.
How do you prepare hydrogen, what are its physical properties, uses and the test for hydrogen?
We prepare hydrogen by reacting zinc or magnesium with dilute hydrochloric acid:
(Look at a diagram of the experiment)
Zn + 2HCl → ZnCl2 + H2
Mg + 2HCl → MgCl2 + H2
hydrogen is insoluble in water, so you can collect it using a gas jar in a trough of water.
dilute hydrochloric acid reacts vigorously with magnesium and can be dangerous.
Physical properties:
Colourless, odourless, less dense than air.
Uses:
Meteorological balloons, rockets, as a clean fuel.
Test:
Light a splint and apply it to the gas, if it is hydrogen there will be a pop.
How do you prepare oxygen, what are its physical properties, uses and test?
Oxygen can be made from hydrogen peroxide, which decomposes slowly to form water and oxygen:
hydrogen peroxide → water + oxygen
2H2O2(aq) → 2H2O(l) + O2(g)
The rate of reaction can be increased using a catalyst, manganese(IV) oxide. When manganese(IV) oxide is added to hydrogen peroxide, bubbles of oxygen are given off.
To make oxygen in the laboratory the same apparatus that was used for the preparation of hydrogen is used. Hydrogen peroxide is poured into a conical flask containing some solid manganese(IV) oxide. Hydrogen peroxide is a colourless solution and manganese(IV) oxide is a black solid.
Instead of the gas jar and water bath, a gas syringe could be used to collect the oxygen.
Physical properties:
Colourless
Odourless
About same density as air (slightly denser)
Uses:
Breathing apparatus
Welding
Test:
A glowing splint applied to a sample of oxygen gas will relight.
How do you prepare carbon dioxide, what are its uses and what is the test for it?
It is formed using the same apparatus as before using solid calcium carbonate and hydrochloric acid
CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
Uses:
Fire extinguisher, carbonated drinks, dry ice.
Test:
When CO2 is bubbled through limewater the limewater has a colour change from clear to cloudy/milky.
