Gases In The Air Flashcards
Write down the main components of air and their approximate percentages in the atmosphere Nitrogen Oxygen Carbon dioxide Argon Noble gases Water vapour
- about 78% nitrogen; • about 21% oxygen; • about 0.03–0.04% carbon dioxide; • about 1% argon; • small proportions of other noble gases; and • varying proportions of water vapour;
Observations when sulfur burns (3)
Yellow, solid Sulfur melts to a red liquid
Burns with a blue flame
Colourless pungent Gas Sulfur dioxide
Why is nitrogen unreactive (inert) (2)
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
Uses of nitrogen (2)
Coolant (liquid) Food packaging (gas)
Physical properties of nitrogen (3)
- colourless, odourless gas
- neutral (pH 7)
- insoluble in Water
- Lack of reactivity due to its triple covalent bond
Diagram of ammonia
Nitrogen atom (5) (one lone pair) Bonded with 3 hydrogen atoms
Physical properties of ammonia (4)
- colourless gas
- characteristic pungent smell
- less dense than air
- very soluble in water
Describe the test for ammonia
- a glass rod dipped in concentrated hydrochloric acid will form white smoke of ammonium chloride as the only product
Give the symbol equation for the test for ammonia
HCl (g) + NH3(g) —> NH4Cl(s)
Equations for making fertiliser out of ammonia (2)
2NH3 + H2SO4 —> (NH4)2SO4
ammonia + sulfuric acid —> ammonium Sulfate
NH3 + HNO3 —> NH4NO3
Ammonia + nitric acid —> ammonia nitrate (100% atom economy)
Advantages of nitrogenous fertilisers (2)
- Greater nitrogen uptake by plant, producing larger, healthier plants
- Increase crop yield therefore increases profits
Disadvantages of nitrogenous fertilisers (2)
- if fertiliser 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
List the impacts of eutrophication caused by nitrogenous fertilisers (4)
- excess algae growth
- leads to death of algae
- microorganisms use oxygen to break down algae
- lack of oxygen in water kills fish
Testing for metal ions with Aqueous Ammonia;
Mg2+
Al3+
Zn2+
Mg2+ colour of precipitate: white Solubility in excess NH4OH: no Ionic equation: Mg2+ + 2OH- —> Mg(OH)2 [insoluble in both reagants]
Al3+ colour of precipitate: white Solubility in excess NH4OH: no Ionic equation: Al3+ + 3OH- —> Al(OH)3 [will not dissolve in excess with ammonia]
Zn2+ colour of precipitate: white Solubility in excess NH4OH: yes, colourless solution Ionic equation: Zn2+ + 2OH- —> Zn(OH)2 [soluble in excess in both reagents]
Describe the laboratory preparation and collection of hydrogen using zinc (5)
- Zinc metal and hydrochloric acid in conical flask
- thistle funnel in conical flask (to add hydrochloric acid)
- collect hydrogen through delivery tube
- gas goes into beehive shelf in water trough
- Gas travels up into gas jar
Physical properties of hydrogen (4)
- Colourless, odourless gas
- less dense than air
- insoluble in water
- neutral
Uses of hydrogen (3)
- weather balloons
- hardening vegetable oils- makes margarine
- Potential clean fuel
Clean fuel
A clean fuel is one which when burned does not produce any toxic or polluting products
Benefits of hydrogen as a fuel
- clean burning fuel, only produces water therefore causes no pollution
- can be used safely in fuel cells
Drawbacks and risks of hydrogen as fuel (4)
- hydrogen must be manufactured as it doesn’t occur naturally in large quantities
- difficult to transport and store (extremely flammable gas and leaks are hard to detect as it is colourless, odourless)
- Hydrogen used in fuel cells must be liquefied and stored under pressure in the vehicles which is expensive
- Methods of hydrogen production for fuel cells can be highly polluting (burning methane releases CO2 a greenhouse gas)
Describe the laboratory preparation and collection of oxygen by the catalytic decomposition of hydrogen peroxide
- Calcium carbonate and hydrogen solid in hydrogen peroxide liquid in a conical flask
- thistle funnel to add manganese (IV) oxide
- reacts to form carbon dioxide through delivery tube into gas jar in the water trough
List the physical properties of oxygen (5)
- Gas
- Colourless
- Odourless
- Slightly soluble in water
- Neutral
Uses of oxygen
- Medicine ; breathing apparatus
- Welding
- Rocket fuel
Describe the reaction of oxygen with hydrogen, carbon, sulfur, magnesium, iron and copper and classify the products as acidic or basic (6)
- Hydrogen - 2H2 + O2 —> 2H2O A combustion reaction - carbon ; C + O2 —> CO2 Acidic gas. Dissolved in water to form a weakly acidic solution of carbonic acid Carbon monoxide is an exception. It is a non-metal oxide neutral gas - Sulfur ; S(s) + O2(g) —> SO2 (g) Acidic non-metal oxide - Magnesium ; 2Mg(s) + O2 (g) —> 2MgO (s) Basic metal oxide - Iron ; 3Fe + 2O2 —> Fe3O4 Basic metal oxide - Copper ; 2Cu + O2 —> 2CuO basic metal oxide
Describe the laboratory preparation and collection of carbon dioxide gas using calcium carbonate and hydrochloric acid (3)
- Calcium carbonate solid in hydrochloric acid in conical flask
- Carbon dioxide travels through delivery tube into beehive shelf in water trough
- Bubbles of CO2 seen in gas jar
Observation of carbon dioxide reaction with calcium hydroxide solution
When bubbled into limewater the carbon dioxide causes the limewater to change from colourless to milky white
Excess CO2 reaction
When carbon dioxide, calcium carbonate and water react together the milky white suspension changes back to a colourless solution
Uses of carbon dioxide (3)
- fire extinguisher
- in carbonated drinks
- dry ice
Physical properties of carbon dioxide (5)
- colourless
- odourless
- Heavier than air
- slightly soluble in water
- acidic gas
Show the symbol equation for the chemical reaction of carbon dioxide with water
CO2 + H2O —> H2CO3 weak carbonic acid
Preparation of carbon dioxide symbol equation
CaCO3 + 2HCl —> CaCl2 + CO2 + H2O
Carbon dioxide is prepared from calcium carbonate marble chips and hydrochloric acid
Test for carbon dioxide common name and chemical name
Limewater, Ca(OH)2 calcium hydroxide
Test for hydrogen
Apply a lit splint
Burns with a squeaky pop