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