Water & Air Flashcards
What type of substances are formed when burnt in air?
Oxides
Are oxides of non-metals acidic / non acidic?
Acidic
Acid + Carbonate = ?
A salt + water
What are the 2 types of salts than can exist?
Anhydrous and hydrated
Describe a chemical test for identifying water.
Add the liquid to anhydrous cobalt (II) chloride. Turns pink to blue. Cobalt (II) chloride paper can also be used. CoCl2(s) +6H2O(l) becomes CoCl2.6H2O(s)
Describe a chemical test for identifying water (2)
Add the liquid to be tested to anhydrous copper (II) sulphate solid. The powder turns from white to blue as hydrated sopper (II) sulphate forms. CuSO4(s) + 5H2O (l) CuSO4. 5H2O (s)
Describe the water cycle
Water evaporates from the sea Water vapor condenses to form clouds Water droplets in the clouds come large enough to fall as rain Water falls on the land and rivers and seas flow the water back to the sea.
What happens to the demand for drinking water as the population rise?
It increases.
Describe how water is processed to make it suitable for drinking
Water goes from reservoirs to a treatment plant Filtered through coarse gravel to remove large bits of dirt Filtered through beds of fine gravel and sand to remove small particles Chlorine is passed through it to kill bacteria (in some areas also sodium fluoride is added to stop tooth decay) Water is supplied to homes and industry
Which gases in what % is clean air composes of?
Nitrogen 78% Oxygen 21% Argon 0.9% Carbon dioxide 0.04% Trace amounts of other noble gases and water vapour 0.06%
Which cycles keep the composition of air stable?
Nitrogen cycle and carbon cycle.
How long has air had its current composition?
200 million years
What type of impurities does water contain before treatment?
Soluble (dissolved calcium, metal compounds, inorganic pollutants) and insoluble (soil, pieces of plant other organic matter).
What are examples of diseases in untreated water?
Cholera and typhoid
Name some common pollutant gases that occur in the air?
Carbon monoxide, sulphur dioxide, oxides of nitrogen and lead compounds from leaded petrol.
What gas are the various forms of rust protection trying to exclude?
Oxygen
Name 4 types of rust protection
Galvanizing/sacrificial protection, painting, plastic coating, covering with grease/oil
Which gases contribute to climate change?
Carbon dioxide and methane
Describe the separation of oxygen and nitrogen by fractional distillation.
Air is filtered to remove the dust Air is cooled to -80oC so Carbon dioxide and water vapour solidify and can be removed. Air is cooled further compressed and then allowed to expand quickly. Causes further cooling. At -200 oC the air becomes liquid. The air is fractionally distilled using a fractionating column which separates liquids with different boiling points. Boiling point of oxygen -183 oC Boiling point of argon -186 oC Boiling point of nitrogen -196 oC
Name 2 commercial uses for oxygen
Medical – supporting patients with breathing difficulties. (There has been a shortage of oxygen during Covid.) Mixed with hydrocarbons such as ethyne for use in cutting tools
Name 2 commercial uses for nitrogen
It is very unreactive – used in food packaging to stop oxidation and decay. (e.g. bags of lettuce leaves stay fresh for longer.) Used to reduce fire hazards in military aircraft systems. Used in production of ammonia. Used in production of silicon chips.
How is water used in industry?
Coolant for industrial processes e.g. nuclear power plant. Watering crops. As a solvent in many chemical production processes. Hydro electric power stations to generate electricity.
What are the uses of water in homes?
Drinking, cooking and washing, general sanitation, car radiators, for gardens and plants.
What problems arise when the supply of water in inadequate?
Food shortages and famine due to the lack of crops Spread of bacteria and disease as drinking water becomes infected due to poor sanitation.
(pollutants) What is a significant source of carbon monoxide production?
incomplete combustion of fossil fuels e.g: incomplete combustion of gasoline: C8H18 + 9O2 → 5CO + 2CO2 + 9H2O
(pollutants) What are the adverse effects of breathing in carbon monoxide?
It is poisonous, combining with haemoglobin in blood and prevents it from carrying oxygen.
(pollutants) What are sources of sulfur dioxide?
Combustion of fuels, natural gas and sulfide ores e.g: zinc blende (ZnS) in the extraction of zinc: 2ZnS + 3O2 → 2ZnO + 2SO2
(pollutants) Name some adverse effects of sulfur dioxide.
Acid rain which causes corrosion to metal structures, buildings and statues made of carbonate rocks, damage to aquatic organisms. Pollutes crops and water supplies, irritates lungs, throats and eyes.
(pollutants) Name some sources of oxides of nitrogen.
reaction of nitrogen with oxygen in car engines and high-temperature furnaces and as a product of bacterial action in soil
(pollutants) Name some adverse effects of oxides of nitrogen.
Acid rain with similar effects as SO2 as well as producing photochemical smog and breathing difficulties, in particular for people suffering from asthma.
(pollutants) Name some sources of oxides of compounds of lead.
old water pipes, old paints, petrol in some kinds of racing cars and from very old engines
(pollutants) Names some sources of compounds of lead.
Causes significant damage to the central nervous system, young infants are particularly susceptible to lead poisoning.
What are catalytic converters?
Cars are fitted with catalytic converters which form a part of their exhaust systems Their function is to render poisonous exhaust gases harmless (e.g. carbon monoxide (CO), Nitrous oxide (NO) and nitrogen dioxide (NO2).
How do catalytic converters work?
They contain a series of transition metal catalysts including platinum and rhodium The metal catalysts are in a honeycomb 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 Nitrogen oxides are reduced to N2 gas: 2NO → N2 + O2 2NO2 → N2 + 2O2 Unburned hydrocarbons are oxidised to carbon dioxide and water: C8H18 + 12½O2 → 8CO2 + 9H2O
Give the word and chemical equation for the rusting of iron.
Iron + Water + Oxygen → Hydrated Iron (III) Oxide 4Fe(s) + 3O2(g) + xH2O(l) → 2Fe2O3.xH2O(s)
What 2 items must be present for the rusting of iron to occur?
Water and iron.
Describe the rusting of iron
Rust is a chemical reaction between iron, water and oxygen to form the compound iron (III) oxide
Does rusting occur faster in salty water?
Rusting is a redox process and it occurs faster in salty water since the presence of sodium chloride increases the electrical conductivity of the water.
What happens if coatings used to prevent rusting are scratched or washed away?
If the coatings are washed away or scratched, the iron is once again exposed to water and oxygen and will rust
How does galvanising/sacrificial protection work?
Iron can be prevented from rusting using the reactivity series. Galvanising is a process where the iron to be protected is coated with a layer of zinc. ZnCO3 is formed when zinc reacts with oxygen and carbon dioxide in the air and protects the iron by the barrier method. If the coating is damaged or scratched, the iron is still protected from rusting by the sacrificial method (magnesium can also be used). This is because zinc is more reactive than iron and so it loses its electrons more readily: Zn → Zn2+ + 2e- The iron stays protected as it accepts the electrons released by zinc, remaining in the reduced state and thus it does not undergo oxidation. The electrons donated by the zinc react with hydrogen ions in the water producing hydrogen gas: 2H+ + 2e- → H2 Zinc therefore reacts with oxygen and water and corrodes instead of the iron.
Give an exmaple where sacrifical protection from rusting is used
Ships hulls have zinc bars attached to them.
Explain sacrifical protection
Iron is covered by or put close to another metal higher in the reactivity series. Normally zinc.
Name a common source of carbon monoxide
incomplete combusiotn of fuels such as in a motor car
Methane is a greenhouse gas. Name 2 sources of methane
It is a major component of natural gas. it is also prodcued by decaying plants and ruminant animals such as cows.
name 2 gases responsible for causing acid rain. For each gas name the acid they form.
Sulfur dioxide forms sulfuric acid
nitrogen oxide forms nitric acid
Name another major greenhouse gas which is not methane
Carbon dioxide
List 3 problems caused by acid rain in the environment
harming plants and fish in lakes
damaging buildings made of metal or limestone.
depleteing the soil of nutrients
what is the balanaced equation showing how nitorgen monoxide is formed in the high temperature of a car engines
N2 (g) + O2 (g) to 2NO (g)
What does anhydrous mean?
Without water
What temperature and pressure are used in the Haber process?
450oC 200 atmospheres
What are greenhouse gases?
Gases that trap heat.
Carbon dioxide, methane, nitrous oxide, fluorinated gases (methane traps 25x more heat than carbon dioxide.)
How is bio gas made?
Biodigesters convert organic material into liquid fertilizer and bio gas.
They offer a cheap source of fuel and help reduce environmental pollution and disease by using manure from animals.
How much methane is in renewable bio gas?
40-70%
How is methane created naturally? (e.g. North sea bed, Siberia)
Decay of plant matter where there is no oxygen (anaerobic decay).
What is natural gas (gas used as fuel) make up of mainly?
97% methane.
What does acid rain do?
This acid erodes stone and metal structures.
Harms plants that take up acidifed water
Harms animals that live in rivers and lakes.
Washes ions such as calcium and magnesium out of the soil depleting minerals available to plants.
How is acid rain caused?
Burning fossil fuels give of gasses including sulfur dioxide and nitrogen dioxide
They combine with water and oxygen to form sulfuric and nitric acid.
What is ammonia used in?
Cleaning agents and fertilisers.
What is the Haber Process?
Process by which ammonia is made industrially.
N2 (g) +3H2 (g) to 2NH3 (g) △H (exothermic reaction)
Nitorgen and hydrogen are introduced to a converter that has 200x atmospheric pressure, heats to 450oC and uses an iron catalyst. Ammonia is formed.
72% of the reactants do not react the first time and are recycled to react again.
Describe the nitrogen cycle
Nitrogen compounds in plants are eaten by animals
Animal bodies and excretions is decompose
Nitrifying bacteria fix the nitrogen into the soil.
Nitrogen compounds are taken in by plants.
What do artificial plant fertilizers used by farmers contain?
Most are nitrates or ammonium compounds. Some other fertilizers contain potassium nitrates or phosphates.
In what form do plants and animals use nitrogen
Nitrates - NO3- ions
Describe the carbon cycle
3 key processes:
Combustion – burning fossil fuels react with carbon
Respiration – in living things carbohydrates react with oxygen to form carbon dioxide
Photosynthesis – in the presence of light plants absorb carbon dioxide and produce oxygen
