C11 - Air and water Flashcards
Two types of tests for water
- Using cobalt(II) chloride
- Using copper(II) sulfate
Copper(II) sulfate test for water
Anhydrous (contains no water) copper(II) sulfate turns white to blue on the addition of water
* Equation: anhydrous copper(II) sulfate + water -› hydrated copper(II) sulfate
* CuSO4 (s) + 5H2O (l) -› CuSO4.5H2O (s)
Cobalt(II) chloride test for water
Cobalt(II) chloride turns blue to pink on the addition of water. This test is usually done using cobalt chloride paper
* Equation: anhydrous cobalt(II) chloride + water -› hydrated cobalt(II) chloride
* CoCl2 (s) + 6H2O (l) -› CoCl2.6H2O (s)
Water supply
Water is taken from rivers, reservoirs or underground water sources (groundwater)
Aquifer
A rock that stores water
Filtration
The process used to remove smaller particles by passing the water through layers of sand and gravel filters that trap solid particles
Chlorination
The careful addition of chlorine to the water supply which kills bacteria and other unwanted microorganisms
Composition of air (4 components)
- 78% nitrogen
- 21% oxygen
- 0.04% CO2
- 0.9% argon and other substances
Uses of air and its components (name 2)
- The noble gases are used in many applications, e.g. helium is used to fill balloons, argon is used in tungsten light bulbs, krypton is used in lasers for eye surgery
- Oxygen is used in steel making, welding and breathing apparatus
- Nitrogen is used in food packaging, the production of ammonia and in the production of silicon chips
- Oxygen and nitrogen are separated from the air by fractional distillation
Common pollutants in air (3)
- Carbon monoxide
- Sulfur dioxide
- Oxides of nitrogen
Source and adverse effects of carbon monoxide
- Source: incomplete combustion of carbon-containing fuels such as fossil fuels
- Adverse effects: toxic, combining with haemoglobin in the blood and prevents it from carrying oxygen
Source and adverse effects of sulfur dioxide
- Sources: combustion of fossil fuels containing sulfur compounds (such as power stations)
- Adverse effects: dissolves in rain to form acid rain with similar effects as the acid rain caused by oxides of nitrogen
Sources and adverse effects of oxides of nitrogen
- Source: reaction of nitrogen with oxygen in the presence of high temperatures (car engines, furnaces, lightning)
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Adverse effects:
- Produces photochemical smog
- Dissolves in rain to form acid rain which causes corrosion to metal infrastructure, damage to aquatic organisms etc.
Examples of greenhouse gases (2)
Carbon dioxide and methane
Process of the greenhouse effect
- The Sun emits energy in the form of radiation that enters the Earth’s atmosphere
- Some thermal energy is reflected from the Earth’s surface
- Most thermal energy is absorbed and re-emitted back from the Earth’s surface
- The energy passes through the atmosphere where some thermal energy passes straight through and is emitted into space
- But some thermal energy is absorbed by greenhouse gases such as carbon dioxide and methane and is re-emitted in all directions
- This reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm
Enhanced greenhouse effect
As the concentration of greenhouse gases in the atmosphere increases due to human activity, more thermal energy is trapped within the Earth’s atmosphere causing the Earth’s average temperature to rise (global warming)
Ways to reduce emissions of sulfur dioxide (2)
- Using fueld which contain low levels of sulfur
- Fuel gas desulfurisation - reacting the sulfur dioxide emitted from burning fuels containing sulfur with calcium oxide therefore removing it from the flue gas
Use of catalyctic converters
- They contain a series of transition metal catalysts including platinum and rhodium
- The metal catalysts are in a honeycomb structure within the converter to increase the surface area available for reaction
- A series of redox reactions occurs which neutralises the pollutant gases
- Carbon monoxide is oxidised to carbon dioxide - 2CO + O2 → 2CO2
- Oxides of nitrogen are reduced to nitrogen gas - 2NO2 → N2 + 2O2
- Overall equation - 2NO + 2CO → N2 + 2CO2
Rusting
A chemical reaction between iron, water and oxygen to form the compound hydrated iron(III) oxide (rust)
* iron + water + oxygen → hydrated iron(III) oxide
Rust barrier methods (4 examples)
- Grease
- Oil
- Paint
- Plastic
- Metal plating
- Zinc galvanising
Contents of fertilisers (3)
Fertilisers contain nitrogen, potassium and phosphorus
Nitrogen (use)
Nitrogen makes chlorophyll and protein and promotes healthy leaves
Potassium (use)
Potassium promotes growth and healthy fruit and flowers
Phosphorus (use)
Phosphorus promotes healthy roots
Ammonia manufacturing (Haber process)
- Stage 1: H2 and N2 are obtained from natural gas and the air respectively and are pumped into the compressor through pipe
- Stage 2: The gases are compressed to about 200 atmospheres inside the compressor
- Stage 3: The pressurised gases are pumped into a tank containing layers of catalytic iron beds at a temperature of 450 °C. Some of the hydrogen and nitrogen react to form ammonia: N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
- Stage 4: Unreacted H2 and N2 and the product ammonia pass into a cooling tank. The ammonia is liquefied and removed to pressurised storage vessels
- Stage 5: The unreacted H2 and N2 gases are recycled back into the system and start over again
Source of hydrogen in Haber process
Reaction of methane with steam
Source of nitrogen in Haber process
The air
Conditions for high yield in Haber process
- low temperature
- high pressure
- catalyst of iron to speed up the reaction
