UNIT 10 Chemistry of the environment [self-taught]

Question 1

one use of water

• in the home
• industrial

Answer 1

• washing / cooking / cleaning / sanitation
• cooling / as a solvent

Question 2

chemical tests for water

Answer 2

anhydrous / blue cobalt (II) chloride goes pink

anhydrous / white copper (II) sulfate goes blue

MP 0, BP 100

Question 3

what do impurities do to BP

Answer 3

increase the boiling point of water, so above 100 oC

Question 4

& to MP

Answer 4

decrease the melting point of water, below 0 oC

Question 5

eqns for cobalt (II) chloride

SIXXX MOLES OF WATER

Answer 5

• anhydrous cobalt(II) chloride + water ⇌ hydrated cobalt(II) chloride

CoCl2 (s) + 6H2O (l) ⇌ CoCl2*6H2O (s)

Question 6

eqns for copper (II) chloride - COPPER 5 COPPER 5

Answer 6

anhydrous copper(II) sulfate + water ⇌ hydrated copper(II) sulfate

CuSO4 (s) + 5H2O (l) ⇌ CuSO4*5H2O (s)

Question 7

WHY distilled water (water that has been heated to form a vapour, and then condensed back to a liquid)

.. is used in practical chemistry rather than tap water

Answer 7

it contains fewer chemical impurities

• if impure, could interfere with chemical reactions

Question 8

unpolluted air - gases

Answer 8

78% nitrogen
21% oxygen
approx 1% argon
0.04% co2
remainder: other gases

Question 9

one environmental consequence of an increase in the percentage of carbon dioxide

Answer 9

global warming / ice-caps melting

• water levels rise as glaciers melt bc of high temperatures, causing flooding in low-lying countries
• extinction of species due to the destruction of natural habitats
• migration of species as they will move to areas that are more habitable (no droughts)
• spread of diseases caused by warmer climate

-loss of habitat due to climate change

Question 10

State that water from natural sources may
contain substances, including:

Answer 10

dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, nitrates from fertilisers, phosphates from fertilisers and detergents

Question 11

some (2) substances beneficial - which? why?

Answer 11

• dissolved oxygen for aquatic life
• some metal compounds provide essential minerals for life

Question 12

some (4) of these substances are
potentially harmful

Answer 12

• some metal compounds are toxic
• some plastics harm aquatic life
• sewage contains harmful microbes which
  cause disease
• nitrates and phosphates lead to
  deoxygenation of water and damage to
  aquatic life

Question 13

treatment of domestic water supply (filtration -> carbon -> chlorination)

1. sedimentation / filtration -

to remove solid, insoluble impurities

Answer 13

water is pumped into sedimentation tanks and allowed to stand for a few hours

mud, sand and other particles will fall to the bottom of the tank due to gravity and form a layer of sediment

the water is then filtered through sand and gravel to remove smaller particles

Question 14

2. filtration / treatment with carbon

Answer 14

removes unpleasant tastes and odours

Question 15

3. chlorination

Answer 15

Bacteria and other microorganisms are too small to be trapped by the filters

so chlorine is carefully added to the water supply to kill bacteria and other microorganisms

Question 16

what is used as fertilisers

e.g., NH4NO3, (NH4)3PO4, KNO3

Answer 16

ammonium salts and nitrates are used
as fertilisers

Question 17

NPK? for?

Answer 17

nitrogen, potassium and phosphorus

for improved plant growth

Question 18

functions & sources -

1. nitrogen

Answer 18

makes chlorophyll and protein and promotes healthy leaves

• NH4+ and NO3-, are sources of soluble nitrogen

Question 19

2. potassium

Answer 19

promotes growth and healthy fruit and flowers

• Most common potassium compounds dissolve in water, produce K+

Question 20

3. phosphorus

Answer 20

promotes healthy roots

• Phosphate ions, PO43- are a source of soluble phosphorus

Question 21

source of each of these FIVE air pollutants

1. CO2

Answer 21

from the complete combustion of carbon-containing fuels

e.g, methane COMPLETE
CH4 + 2O2 → CO2 + 2H2O

Question 22

2. CO & particulates

Answer 22

from the incomplete combustion of carbon-containing fuels

e.g. INCOMPLETE - gasoline/octane, methane (C & CO)
C8H18 + 9O2 → 5CO + 2CO2 + 9H2O

2CH4 + 3O2→ 2CO + 4H2O
CH4 + O2→ C + 2H2O

Question 23

3. CH4 (methane)

Answer 23

from the decomposition of vegetation and waste gases from digestion in animals

Question 24

4. oxides of nitrogen

Answer 24

from car engines -

nitrogen and oxygen react in the high pressure and temperature conditions of internal combustion engines and blast furnaces

Question 25

5. SO2 (sulfur dioxide)

Answer 25

from the combustion of fossil fuels which contain sulfur compounds

Question 26

adverse effect of these SIX air pollutants 1. CO2 & 4. methane

Answer 26

higher levels of carbon dioxide/methane leading to increased global warming, which leads to climate change

Question 27

2. CO

Answer 27

toxic gas -combines with haemoglobin in the blood and prevents it from carrying oxygen

Question 28

3. particulates

Answer 28

increased risk of respiratory problems and cancer

Question 29

5. oxides of nitrogen

Answer 29

📌 acid rain [dissolves in rain to form acid rain which causes corrosion to metal structures & damage to aquatic organisms], 📌 produces photochemical smog 📌 respiratory problems

Question 30

6. SO2

Answer 30

acid rain

Question 31

sun emits energy... how is thermal energy reflected/absorbed/emitted?

Answer 31

Sun's rays enter 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, where some thermal energy passes straight through and is emitted into space

Question 32

thermal energy is _____ by greenhouse gases...

Answer 32

📌 some thermal energy is absorbed by greenhouse gases, such as carbon dioxide and methane, and is re-emitted in all directions

Question 33

what does this do? what is it called?

Answer 33

reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm greenhouse effect

Question 34

what is enhanced greenhouse effect?

Answer 34

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)

Question 35

strategies to reduce the effects of 1. climate change

Answer 35

planting trees, reduction in livestock farming, decreasing use of fossil fuels, increasing use of hydrogen and renewable energy, e.g. wind, solar

Question 36

of 2. acid rain

Answer 36

use of catalytic converters in vehicles, reducing emissions of sulfur dioxide by using low-sulfur fuels and flue gas desulfurisation with calcium oxide

Question 37

flue gas desulfurisation

Answer 37

- waste gases from coal fired power stations are passed into a scrubbing chamber - they are sprayed with a wet slurry of calcium oxide and calcium carbonate - the calcium compounds react with sulfur dioxide to produce calcium sulfate

Question 38

catalytic converters

Answer 38

- contain a series of transition metal catalysts including platinum and rhodium - metal catalysts are in a honeycomb within the converter to increase the surface area available for reaction

Question 39

series of redox reactions, neutralise pollutant gases - EACH STEP & EQN

Answer 39

1. Carbon monoxide is oxidised to carbon dioxide: 2CO + O2 → 2CO2

Question 40

2.

Answer 40

oxides of nitrogen are reduced to N2 gas: 2NO → N2 + O2 2NO2 → N2 + 2O2

Question 41

3.

Answer 41

- summarise the reaction of nitrogen monoxide and carbon monoxide within a catalytic convertor: 2NO + 2CO → N2 + 2CO2

Question 42

4. 12.5 OXYGENS.

Answer 42

Unburned hydrocarbons can also be oxidised to carbon dioxide and water: C8H18 + 12½O2 → 8CO2 + 9H2O

Question 43

photosynthesis

Answer 43

the reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light

Question 44

word & symbol eqns

Answer 44

- carbon dioxide + water → glucose + oxygen - 6CO2 + 6H2O → C6H12O6 + 6O2