UNIT 10 Chemistry of the environment [self-taught] Flashcards
one use of water
- in the home
- industrial
- washing / cooking / cleaning / sanitation
- cooling / as a solvent
chemical tests for water
anhydrous / blue cobalt (II) chloride goes pink
anhydrous / white copper (II) sulfate goes blue
MP 0, BP 100
what do impurities do to BP
increase the boiling point of water, so above 100 oC
& to MP
decrease the melting point of water, below 0 oC
eqns for cobalt (II) chloride
SIXXX MOLES OF WATER
- anhydrous cobalt(II) chloride + water ⇌ hydrated cobalt(II) chloride
CoCl2 (s) + 6H2O (l) ⇌ CoCl2*6H2O (s)
eqns for copper (II) chloride - COPPER 5 COPPER 5
anhydrous copper(II) sulfate + water ⇌ hydrated copper(II) sulfate
CuSO4 (s) + 5H2O (l) ⇌ CuSO4*5H2O (s)
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
it contains fewer chemical impurities
- if impure, could interfere with chemical reactions
unpolluted air - gases
78% nitrogen
21% oxygen
approx 1% argon
0.04% co2
remainder: other gases
one environmental consequence of an increase in the percentage of carbon dioxide
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
State that water from natural sources may
contain substances, including:
dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, nitrates from fertilisers, phosphates from fertilisers and detergents
some (2) substances beneficial - which? why?
- dissolved oxygen for aquatic life
- some metal compounds provide essential minerals for life
some (4) of these substances are
potentially harmful
- 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
treatment of domestic water supply (filtration -> carbon -> chlorination)
- sedimentation / filtration -
to remove solid, insoluble impurities
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
- filtration / treatment with carbon
removes unpleasant tastes and odours
- chlorination
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
what is used as fertilisers
e.g., NH4NO3, (NH4)3PO4, KNO3
ammonium salts and nitrates are used
as fertilisers
NPK? for?
nitrogen, potassium and phosphorus
for improved plant growth
functions & sources -
- nitrogen
makes chlorophyll and protein and promotes healthy leaves
- NH4+ and NO3-, are sources of soluble nitrogen
- potassium
promotes growth and healthy fruit and flowers
- Most common potassium compounds dissolve in water, produce K+
- phosphorus
promotes healthy roots
- Phosphate ions, PO43- are a source of soluble phosphorus
source of each of these FIVE air pollutants
- CO2
from the complete combustion of carbon-containing fuels
e.g, methane COMPLETE
CH4 + 2O2 → CO2 + 2H2O
- CO & particulates
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
- CH4 (methane)
from the decomposition of vegetation and waste gases from digestion in animals
- oxides of nitrogen
from car engines -
nitrogen and oxygen react in the high pressure and temperature conditions of internal combustion engines and blast furnaces
- SO2 (sulfur dioxide)
from the combustion of fossil
fuels which contain sulfur compounds
adverse effect of these SIX air pollutants
- CO2 & 4. methane
higher levels of carbon dioxide/methane leading to increased global warming, which leads to climate change
- CO
toxic gas
-combines with haemoglobin in the blood and prevents it from carrying oxygen
- particulates
increased risk of respiratory problems and cancer
- oxides of nitrogen
📌 acid rain [dissolves in rain to form acid rain which causes corrosion to metal structures & damage to aquatic organisms],
📌 produces photochemical
smog
📌 respiratory problems
- SO2
acid rain
sun emits energy…
how is thermal energy reflected/absorbed/emitted?
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
thermal energy is _____ by greenhouse gases…
📌 some thermal energy is absorbed by greenhouse gases, such as carbon dioxide and methane, and is re-emitted in all directions
what does this do? what is it called?
reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm
greenhouse effect
what is enhanced greenhouse effect?
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)
strategies to reduce the effects
of 1. climate change
planting trees,
reduction in livestock farming,
decreasing use of fossil fuels,
increasing use of hydrogen and renewable energy, e.g. wind, solar
of 2. 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
flue gas desulfurisation
- 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
catalytic converters
- 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
series of redox reactions, neutralise pollutant gases -
EACH STEP & EQN
- Carbon monoxide is oxidised to carbon dioxide:
2CO + O2 → 2CO2
2.
oxides of nitrogen are reduced to N2 gas:
2NO → N2 + O2
2NO2 → N2 + 2O2
3.
- summarise the reaction of nitrogen monoxide and carbon monoxide within a catalytic convertor:
2NO + 2CO → N2 + 2CO2
- 12.5 OXYGENS.
Unburned hydrocarbons can also be oxidised to carbon dioxide and water:
C8H18 + 12½O2 → 8CO2 + 9H2O
photosynthesis
the reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light
word & symbol eqns
- carbon dioxide + water → glucose + oxygen
- 6CO2 + 6H2O → C6H12O6 + 6O2
