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chem in the environment Flashcards

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1
Q

what are the chemical tests for water

A

anhydrous cobalt chloride
anhydrous copper sulfate

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2
Q

what is the positive result of this test

(cobalt chloride)

A

cobalt chloride paper turns blue to pink on addition of water

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3
Q

what is the chemical reaction for this test

(cobalt chloride)

A

cocl2 + 6h2o <—-> cocl2.6h2o

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4
Q

what is the positive result of the anhydrous copper sulfate test

A

anhydrous copper sulfate turns white to blue on the addition of water

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5
Q

what is the reaction for this test

(copper sulfate)

A

CuSo4 + 5h2o <—-> CuSo4.5h2o

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6
Q

how to test for the purity of water

A

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

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7
Q

what is distilled water useful for

A

Distilled water is used in practical chemistry because of its high purity

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8
Q

why is tap water not used in practical chemistry

A

Tap water contains more impurities which could interfere with chemical reactions so is typically not used

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9
Q

how can water be obtained from natural sources

A

lakes, rivers and underground water sources (groundwater)

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10
Q

what is an aquifer

A

A rock that stores water

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11
Q

what can water obtained from natural sources contain

A

Dissolved oxygen
Metal compounds
Plastics
Sewage
Harmful microbes
Nitrates from fertilisers
Phosphates from fertilisers and detergents

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12
Q

which substance found in natural source water can be beneficial

A

Dissolved oxygen - essential for aquatic life
Metal compounds - some provide essential minerals which are necessary for life, such as calcium and magnesium

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13
Q

which subtance found in natural source water can be fatal

A

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

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14
Q

some metal compounds can be beneficial some can be fatal
which is which

A

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

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15
Q

what are the steps to purify water

A

-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

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16
Q

what are the steps of purification of water called

A

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

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17
Q

what elements do artificial fertilizers contain and each elements uses

A

nitrogen - chlorophyll and other proteins
Phosphorus - root growth and crop ripening
potassium - making proteins and to resist diseases

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18
Q

what is a fertilizer

A

any substance added to soil to make it more fertile

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19
Q

what are the reactions to make fertilizers

A

NH3 + HNO3 —-> NH4NO3
Ammonia + Nitric Acid –> Ammonium Nitrate

3NH3 + H3PO4 ——> (NH4)3PO4
Ammonia + Phospheric Acid —> Ammonium Phospate

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20
Q

what is the composition of air

A

78% nitrogen (N2)
21% oxygen (O2)
the remainder is a mixture of noble gasses and CO2

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21
Q

what is the main source of carbon monoxide and the negative impact of it on the environment

A

incomplete combustion of carbon-containing substances
binds with haemoglobin, constricting oxygen supply in cells; leads to fatigue/death. toxic

22
Q

what is the main source of sulfur dioxide and its negative impact on the environment

A

hydrocarbons burned with sulfur impurities/compounds
causes acid rain and bronchospasm in asthmatics

23
Q

what is the main source of nitrogen oxides and its negative impact on the environment

A

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

24
Q

what are the main source of lead and its negative impact on the environment

A

combustion of leaded fuels
Damages brain and nerve cells in young children

25
Q

what is the main source of methane and its negative impact on the environment

A

-Sources of methane: oil and natural gas, decomposition of vegetation, and waste gases from digestion in animals

greenhouse gas– > contributes to global warming

26
Q

what is the main source of carbon dioxide and its negative impact on the environment

A

complete combustion of carbon-containing compounds
global warming/climate change

27
Q

how do greenhouse gasses (carbon dioxide and methane) cause global warming?

A

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

28
Q

what are other ways can carbon dioxide be formed

A

Respiration
Reaction between an acid and a carbonate
Complete combustion of a carbon containing substance
Thermal decomposition of limestone

29
Q

what are the steps of fractional distillation of air

A

-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.

30
Q

what is a catalytic converter and how does it work

A

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

31
Q

ways to counteract climate change

A

planting trees
reduction in livestock farming
decreasing use of fossil fuels
increasing use of hydrogen and renewable energy

32
Q

ways to counteract acid rain

A

use of catalytic converters in vehicles

reducing emissions of sulfur dioxide by using low-sulfur fuels and flue gas

desulfurisation with calcium oxide

33
Q

Describe photosynthesis

A

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

34
Q

Word eqn for photosynthesis

chemical eqn

A

carbon dioxide + water → glucose + oxygen

6CO2 + 6H2O → C6H12O6 + 6O2

35
Q

what are the necessary elements in a fertilizer

A

nitrogen
phosphorus
potassium

36
Q

why is carbon monoxide considered a pollutant

A

it is toxic

37
Q

is carbon monoxide basic, acidic or neutral

A

is a neutral oxide

38
Q

how is flue gas desulfurization done

A

sprinkle calcium hydroxide in chimneys of factories

39
Q

what is the reaction in flue gas desulfurisation

A

so2 + ca(oh)2 —> caso3 + h2o

40
Q

what is done to calcium sulfide so it can be converted to a more useful form

A

react with water and oxygen to form gypsum, used for castings and blasters

2caso3 + 4h2o + o2 —-> 2Caso4.2h2o

41
Q

Products of oxidation of methane

A

Carbon dioxide
Water

42
Q

some industrial uses of water

A

Contact process - sulfuric acid
Production of hydrogen - electrolysis
Hydration of alkenes to form alcohols

43
Q

How is rain water treated before entering water supply

A

(past paper q)

filtration
chlorination

44
Q

Acid rain question -
what does sulfuric dioxide form
what does nitric dioxide form

A

sulfuric dioxide - sulfuric acid

nitric dioxide - nitric acid

45
Q

calcium oxide and calcium carbonate can both neutralise acid (desulfurisation)

Why is calcium oxide a better way to desulphurize than calcium carbonate

A

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

46
Q

where could seaweed obtain the following while growing:

Carbon
hydrogen
chlorine

A

CO2

H2O

Sea water - NaCl (salt)

47
Q

2 compounds in unpolluted air

A

Carbon dioxide
Water

48
Q

harmful effects of acid rain

name 3

A

damage buildings
soil acidification
acidify lakes
kill fish
damage trees
crop loss

49
Q

3 bases to increase ph of soil

A

calcium hydroxide
calcium oxide
calcium carbonate

50
Q

Why is ammonium nitrate prefered over other fertilizers such as ammonium sulfate

A

More nitrogen in Ammonium Nitrate

51
Q

State the essential plant nutrient not supplied by ammonium phosphate.

A

Potassium

52
Q

Why could a fertilizer like urea (CO(NH2)2) not be effective in promoting crop growth

A

only has nitrogen
no phosphorous or potassium

Chem (31 decks)

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