chemistry of the environment Flashcards
chemical test for the presence of water
use anhydrous cobalt (II) chloride and anhydrous copper (II) sulfate
how to test for the purity of water
use melting point and boiling point
why is distilled water used in practical chemistry rather than tap water
because it contains fewer chemical impurities
7 substances from water from natural sources
- dissolved oxygen
- metal compounds
- plastics
- sewage
- harmful microbes
- nitrates from fertilisers
- phosphates from fertilisers and detergents
what substances found in water are beneficial
- dissolved oxygen for aquatic life
- some metal compounds provide essential minerals for life
substances found in water that are potentially harmful to us
- 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
describe treatment of domestic water supply
- sedimentation and filtration to remove solids
- use of carbon to remove tastes and odours
- chlorination to kill microbes
composition of clean, dry air
78% nitrogen
21% oxygen
remainder as a mixture of noble gases and carbon dioxide
what is used as fertilisers
ammonium salts and nitrates
what is the use of NPK fertilisers
provide elements nitrogen, phosphorus and potassium for improved plant growth
what is the source of carbon dioxide
complete combustion of carbon-containing fuels
what is the source of carbon monoxide and particulates
incomplete combustion of carbon containing fuels
source of methane
decomposition of vegetation and waste gases from digestion in animals
sources of oxides of nitrogen
car engines
sources of sulfur dioxide
combustion of fossil fuels which contain sulfur compounds
adverse effect of carbon dioxide
higher levels of carbon dioxide leading to increased global warming, which leads to climate change
adverse effect of carbon monoxide
toxic gas
adverse effect of particulates
increased risk of respiratory problems and cancer
adverse effect of methane
higher levels of methane leading to increased global warming, which leads to climate change
adverse effect of oxides of nitrogen
acid rain, photochemical smog and respiratory problems
adverse effect of sulfur dioxide
acid rain
how do greenhouse gases (carbon dioxide and methane) cause global warming
absorption, reflection and emission of thermal energy. reducing thermal energy loss to space
strategies to reduce effects of climate change
- planting trees
- reduction in livestock farming
- decreasing use of fossil fuels
- increasing use of hydrogen and renewable energy (wind, solar)
strategies to reduce effects of acid rain
- catalytic converters in vehicles
- reducing emissions of sulfur dioxide by using low-sulfur fuels and flue gas desulfurization with calcium oxide
what is photosynthesis
reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light
removal of oxides of nitrogen by catalytic converter equation
. 2CO + 2NO → 2CO2 + N2
what is rust
chemical reaction between iron, water and oxygen to form compound hydrated iron (III) oxide (rust)
what conditions does rust need to form
oxygen and water
what is oxidised during rusting
iron
how to investigate rusting
- 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
how to prevent rust
coat iron with barriers that prevent iron from coming into contact with water and oxygen
common barrier methods
- grease
- oil
- paint
- plastic
what is it called when a metal oxidises that isnt iron or an alloy containing iron
instead of rust, say corroded
what is rust
hydrated iron (III) oxide
what is sacrificial protection
a more reactive metal can be attached to a less reactive metal (more reactive will oxidise, therefore corroding first)
what is galvanisation
process where iron to be protexted is coated with a layer of zinc (done by electroplating/dipping in molten zinc)
what is formed when zinc reacts with oxygen and carbon dioxide, and what does it do
protects iron by barrier method. if coating is damaged/scrated, iron is still protexted by sacrificial protection
