chemistry of the environment

Question 1

chemical test for the presence of water

Answer 1

use anhydrous cobalt (II) chloride and anhydrous copper (II) sulfate

Question 2

how to test for the purity of water

Answer 2

use melting point and boiling point

Question 3

why is distilled water used in practical chemistry rather than tap water

Answer 3

because it contains fewer chemical impurities

Question 4

7 substances from water from natural sources

Answer 4

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

Question 5

what substances found in water are beneficial

Answer 5

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

Question 6

substances found in water that are potentially harmful to us

Answer 6

• 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 7

describe treatment of domestic water supply

Answer 7

• sedimentation and filtration to remove solids
• use of carbon to remove tastes and odours
• chlorination to kill microbes

Question 8

composition of clean, dry air

Answer 8

78% nitrogen
21% oxygen
remainder as a mixture of noble gases and carbon dioxide

Question 9

what is used as fertilisers

Answer 9

ammonium salts and nitrates

Question 10

what is the use of NPK fertilisers

Answer 10

provide elements nitrogen, phosphorus and potassium for improved plant growth

Question 11

what is the source of carbon dioxide

Answer 11

complete combustion of carbon-containing fuels

Question 12

what is the source of carbon monoxide and particulates

Answer 12

incomplete combustion of carbon containing fuels

Question 13

source of methane

Answer 13

decomposition of vegetation and waste gases from digestion in animals

Question 14

sources of oxides of nitrogen

Answer 14

car engines

Question 15

sources of sulfur dioxide

Answer 15

combustion of fossil fuels which contain sulfur compounds

Question 16

adverse effect of carbon dioxide

Answer 16

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

Question 17

adverse effect of carbon monoxide

Answer 17

toxic gas

Question 18

adverse effect of particulates

Answer 18

increased risk of respiratory problems and cancer

Question 19

adverse effect of methane

Answer 19

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

Question 20

adverse effect of oxides of nitrogen

Answer 20

acid rain, photochemical smog and respiratory problems

Question 21

adverse effect of sulfur dioxide

Answer 21

acid rain

Question 22

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

Answer 22

absorption, reflection and emission of thermal energy. reducing thermal energy loss to space

Question 23

strategies to reduce effects of climate change

Answer 23

• planting trees
• reduction in livestock farming
• decreasing use of fossil fuels
• increasing use of hydrogen and renewable energy (wind, solar)

Question 24

strategies to reduce effects of acid rain

Answer 24

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

Question 25

what is photosynthesis

Answer 25

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

Question 26

removal of oxides of nitrogen by catalytic converter equation

Answer 26

. 2CO + 2NO → 2CO2 + N2

Question 27

what is rust

Answer 27

chemical reaction between iron, water and oxygen to form compound hydrated iron (III) oxide (rust)

Question 28

what conditions does rust need to form

Answer 28

oxygen and water

Question 29

what is oxidised during rusting

Answer 29

iron

Question 30

how to investigate rusting

Answer 30

- prepare 3 test tubes - oil in 2nd tube keeps out air and water has been boiled so that no air is left in it - calcium chloride is used in the 3rd test tube to remove any moisture in the air - 1st tube will only have water and air

Question 31

how to prevent rust

Answer 31

coat iron with barriers that prevent iron from coming into contact with water and oxygen

Question 32

common barrier methods

Answer 32

- grease - oil - paint - plastic

Question 33

what is it called when a metal oxidises that isnt iron or an alloy containing iron

Answer 33

instead of rust, say corroded

Question 34

what is rust

Answer 34

hydrated iron (III) oxide

Question 35

what is sacrificial protection

Answer 35

a more reactive metal can be attached to a less reactive metal (more reactive will oxidise, therefore corroding first)

Question 36

what is galvanisation

Answer 36

process where iron to be protexted is coated with a layer of zinc (done by electroplating/dipping in molten zinc)

Question 37

what is formed when zinc reacts with oxygen and carbon dioxide, and what does it do

Answer 37

protects iron by barrier method. if coating is damaged/scrated, iron is still protexted by sacrificial protection