chem in the environment Flashcards
what are the chemical tests for water
anhydrous cobalt chloride
anhydrous copper sulfate
what is the positive result of this test
(cobalt chloride)
cobalt chloride paper turns blue to pink on addition of water
what is the chemical reaction for this test
(cobalt chloride)
cocl2 + 6h2o <—-> cocl2.6h2o
what is the positive result of the anhydrous copper sulfate test
anhydrous copper sulfate turns white to blue on the addition of water
what is the reaction for this test
(copper sulfate)
CuSo4 + 5h2o <—-> CuSo4.5h2o
how to test for the purity of water
pure substances melt and boil at specific temperatures
pure water boils at 100 deg cel
pure water melts at 0 deg cel
impurities tend to increase the boiling temp and decrease the melting temp
so impure water would boil at a temperature higher than 100 and melt at a temperature lower than 0
what is distilled water useful for
Distilled water is used in practical chemistry because of its high purity
why is tap water not used in practical chemistry
Tap water contains more impurities which could interfere with chemical reactions so is typically not used
how can water be obtained from natural sources
lakes, rivers and underground water sources (groundwater)
what is an aquifer
A rock that stores water
what can water obtained from natural sources contain
Dissolved oxygen
Metal compounds
Plastics
Sewage
Harmful microbes
Nitrates from fertilisers
Phosphates from fertilisers and detergents
which substance found in natural source water can be beneficial
Dissolved oxygen - essential for aquatic life
Metal compounds - some provide essential minerals which are necessary for life, such as calcium and magnesium
which subtance found in natural source water can be fatal
Metal compounds - some are toxic like aluminium and lead
Some plastics - may be harmful to aquatic life in many ways, e.g. getting trapped in plastic waste, dying of starvation as their stomach is filled with plastic
Sewage - contains harmful microbes which can cause disease
Nitrate & phosphates from fertilisers - these can promote the growth of aquatic plant life which leads to the deoxygenation of water. Ultimately, this can cause damage to aquatic life in a process called eutrophication
some metal compounds can be beneficial some can be fatal
which is which
calcium, magnesium, potassium and sodium are all metals which are essential for life
lead, arsenic and mercury can be fatal to humans and aquatic life
what are the steps to purify water
-Water is pumped into screens to remove solid insoluble impurities
-Aluminium sulfate or Iron (III) Sulfate (COAGULANTS) is added to make fine suspended particles clump together
- air is blown in through water in flotation tanks so that coagulated particles can be SKIMMED off.
-The water is then filtered through layers of sand and gravel to remove larger, insoluble debris.
-filter water using carbon will remove bad tastes and odours
-Chlorine gas is bubbled into the water to kill bacteria; the acidic effect on the water is reversed by adding an alkali, sodium hydroxide
-Some countries add fluoride to help fight tooth decay
what are the steps of purification of water called
Sedimentation - letting particles falling to the bottom of the container.
Flocculation - addition of a COAGULANT (aluminium sulfate, iron (III) sulfate, etc) to make the smaller particles stick together
filtering through carbon will remove tastes and odours
Chlorination - usage of chlorine to kill bacteria
what elements do artificial fertilizers contain and each elements uses
nitrogen - chlorophyll and other proteins
Phosphorus - root growth and crop ripening
potassium - making proteins and to resist diseases
what is a fertilizer
any substance added to soil to make it more fertile
what are the reactions to make fertilizers
NH3 + HNO3 —-> NH4NO3
Ammonia + Nitric Acid –> Ammonium Nitrate
3NH3 + H3PO4 ——> (NH4)3PO4
Ammonia + Phospheric Acid —> Ammonium Phospate
what is the composition of air
78% nitrogen (N2)
21% oxygen (O2)
the remainder is a mixture of noble gasses and CO2
what is the main source of carbon monoxide and the negative impact of it on the environment
incomplete combustion of carbon-containing substances
binds with haemoglobin, constricting oxygen supply in cells; leads to fatigue/death. toxic
what is the main source of sulfur dioxide and its negative impact on the environment
hydrocarbons burned with sulfur impurities/compounds
causes acid rain and bronchospasm in asthmatics
what is the main source of nitrogen oxides and its negative impact on the environment
high temperatures (eg car engine) that trigger a reaction between N2 and O2
causes respiratory problems
photochemical smog when uv light from sun reacts with the oxides
contributes to acid rain
what are the main source of lead and its negative impact on the environment
combustion of leaded fuels
Damages brain and nerve cells in young children
what is the main source of methane and its negative impact on the environment
-Sources of methane: oil and natural gas, decomposition of vegetation, and waste gases from digestion in animals
greenhouse gas– > contributes to global warming
what is the main source of carbon dioxide and its negative impact on the environment
complete combustion of carbon-containing compounds
global warming/climate change
how do greenhouse gasses (carbon dioxide and methane) cause global warming?
Trap heat inside Earth’s atmosphere, increasing it’s average temperature. Leads to climate change
Causes global warming, melting of polar-caps, rising sea levels, floods and droughts
what are other ways can carbon dioxide be formed
Respiration
Reaction between an acid and a carbonate
Complete combustion of a carbon containing substance
Thermal decomposition of limestone
what are the steps of fractional distillation of air
-Air is filtered for dust
-Cooled to -80℃ to remove CO2 and water vapour (because they would freeze and block the pipes) using absorbent filters.
-Remaining air is cooled to liquify at -200℃. The Noble gases are still in the gaseous state and are removed.
-The (liquid) air, consisting of NO2 and O2, is pumped into the fractional column where it is slowly warmed.
-The remaining components rise and condense in different fractions due to different boiling points and are collected.
what is a catalytic converter and how does it work
Present in car exhausts; contains transition metal catalysts of platinum and rhodium
Aids redox reactions to neutralize toxic pollutants formed as a result of incomplete fuel combustion.
(a) Carbon monoxide
(b) Nitrogen oxides
(c) Unburned hydrocarbons
Reaction equations:
(a) 2CO+ O2→ CO2
(b) 2NO+ 2CO→ N2+ 2CO2
(c) 2C8H18 + 25O2→ 16CO2 + 18H2O
ways to counteract climate change
planting trees
reduction in livestock farming
decreasing use of fossil fuels
increasing use of hydrogen and renewable energy
ways to counteract acid rain
use of catalytic converters in vehicles
reducing emissions of sulfur dioxide by using low-sulfur fuels and flue gas
desulfurisation with calcium oxide
Describe photosynthesis
reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light
inorganic substances to organic compounds
Word eqn for photosynthesis
chemical eqn
carbon dioxide + water → glucose + oxygen
6CO2 + 6H2O → C6H12O6 + 6O2
what are the necessary elements in a fertilizer
nitrogen
phosphorus
potassium
why is carbon monoxide considered a pollutant
it is toxic
is carbon monoxide basic, acidic or neutral
is a neutral oxide
how is flue gas desulfurization done
sprinkle calcium hydroxide in chimneys of factories
what is the reaction in flue gas desulfurisation
so2 + ca(oh)2 —> caso3 + h2o
what is done to calcium sulfide so it can be converted to a more useful form
react with water and oxygen to form gypsum, used for castings and blasters
2caso3 + 4h2o + o2 —-> 2Caso4.2h2o
Products of oxidation of methane
Carbon dioxide
Water
some industrial uses of water
Contact process - sulfuric acid
Production of hydrogen - electrolysis
Hydration of alkenes to form alcohols
How is rain water treated before entering water supply
(past paper q)
filtration
chlorination
Acid rain question -
what does sulfuric dioxide form
what does nitric dioxide form
sulfuric dioxide - sulfuric acid
nitric dioxide - nitric acid
calcium oxide and calcium carbonate can both neutralise acid (desulfurisation)
Why is calcium oxide a better way to desulphurize than calcium carbonate
calcium oxide is soluble in water
calcium carbonate is insoluble
calcium oxide can raise the pH of the water above 7 making it alkaline
calcium carbonate cannot
where could seaweed obtain the following while growing:
Carbon
hydrogen
chlorine
CO2
H2O
Sea water - NaCl (salt)
2 compounds in unpolluted air
Carbon dioxide
Water
harmful effects of acid rain
name 3
damage buildings
soil acidification
acidify lakes
kill fish
damage trees
crop loss
3 bases to increase ph of soil
calcium hydroxide
calcium oxide
calcium carbonate
Why is ammonium nitrate prefered over other fertilizers such as ammonium sulfate
More nitrogen in Ammonium Nitrate
State the essential plant nutrient not supplied by ammonium phosphate.
Potassium
Why could a fertilizer like urea (CO(NH2)2) not be effective in promoting crop growth
only has nitrogen
no phosphorous or potassium
