Gas Chemistry Flashcards
What are the main components of air and their percentage in air?
Nitrogen - 78
Oxygen - 21
Carbon dioxide - 0.03-0.04
Argon - 1
Water vapour - varying proportions
Physical properties and uses of Nitrogen
Physical properties - colourless odourless gas, neutral and insoluble in water
Uses - coolant and food packaging
Structure of nitrogen
It is unreactive due to the strong triple covalent bond in the diatomic molecule. A lot of energy is required to break this bond before the nitrogen atoms could react.
Physical properties of ammonia
Colourless gas, characteristic pungent smell, less dense than air, very soluble in water (fountain experiment)
NH3
What is the ammonia fountain experiment?
Water is injected into flask and ammonia dissolves and reduces pressure in flask and water in a trough rushes up to replace gas.
NH3 + H2O - NH4OH
What is the reaction of ammonia with hydrogen chloride?
Used as a test for ammonia and ammonia reacts with hydrogen chloride to form white fumes of ammonium chloride as the only product, glass rod dipped in concentrated HCl will form white smoke of ammonium chloride.
HCl + NH3 - NH4Cl
What is the reaction of acids with ammonia?
Ammonia is an alkanline gas and will react with acids to form ammonium compounds.
E.g. ammonia + sulfuric acid - ammonium sulfate.
Ammonia + nitric acid - NH4NO3
These are both artificial fertilisers.
Advantages of artificial fertilisers
Greater nitrogen uptake by plant - producing larger, healthier plants.
Increase crop yield therefore increases profits.
Disadvantages of artificial fertilisers
If fertilisers gets into rivers then it contributes to eutrophication.
If gets into drinking water then can cause stomach cancer and condition in infants known as ‘blue baby syndrome’.
What happens with eutrophication?
Excess algae growth.
Leads to death of algae.
Microorganisms use oxygens to break down algae.
Lack of oxygen in water kills fish.
Physical properties and uses of hydrogen
Physical properties - colourless odourless gas, less dense than air, insoluble in water and neutral.
Uses - weather balloons, hardening vegetable oils - make margarine and potential ‘clean’ fuel
Reactions of hydrogen with oxygen and copper oxide
Oxygen - 2H2 + O2 - 2H2O.
Copper oxide - CuO + H2 - Cu + H2O
What is clean fuel?
One which when burned does not produce any toxic or polluting products
Benefits of using hydrogen as fuel
Clean burning fuel - only produces water therefore causes no pollution.
Can be used safely in fuel cells.
Drawbacks and risks of using hydrogen as fuel
Hydrogen must be manufactured as it doesn’t occur naturally in large quantities.
Difficult to transport and store.
Extremely flammable gas.
Physical properties and uses of oxygen
Physical properties - gas, colourless, odourless, slightly soluble in water and neutral.
Uses - medicine - breathing apparatus, welding and rocket fuel.
General rule of burning metals and non-metals in oxygen
Metals burn in oxygen to product metal oxides which are basic.
Non-metals burn in oxygen producing non-metal oxides which are acidic.
Exceptions are water and carbon monoxide.
Physical properties and uses of carbon dioxide
Physical properties - colourless odourless gas, heavier than air, slightly soluble in water and acidic gas.
Uses - fire extinguisher, in carbonated drinks and dry ice.
Reaction of carbon dioxide with calcium hydroxide (limewater) and calcium carbonate
Limewater - CO2 + Ca(OH)2 - CaCO3 + H2O - test for CO2
Calcium carbonate - CO2 + CaCO3 + H2O - Ca(HCO3)2
Chemical reaction of carbon dioxide with water and burning magnesium
Water - CO2 + H2O - H2CO3 (weak carbonic acid).
Magnesium - 2Mg + CO2 - 2MgO + C
