Transcript Environmental Chemistry 2

Environmental Chemistry 2
Acids & Bases
Pg.197
Acids & bases are used everyday and
within our bodies.
 They are used for distinct roles & tastes.
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Eg. HCL is used in your stomach for digestion
(very strong acid)
 Phosphoric acid is used in carbonated drinks
as a flavoring agent and gives food a tangy
flavor. (like cheese, jams, jelly)
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Identifying Acids & Bases
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You can identify acids &
bases by:
Taste
*not useful if unknown
 Touch
*not useful if unknown
 Chemical indicator 
litmus (mixture of plant
compounds extracted from
lichens)
Acid
Base
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Litmus turns red acid
blue  base
Usually called litmus
paper
Taste sour
Eg. lemons
Taste bitter
Eg.
Celery,horse
radish
Litmus red
Slippery/greasy
Litmus - blue
pH Scale
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pH – strength of hydrogen
pH is the strength of an acid or base
pH <7 is an acid
pH>7 is a base
pH of 7 is neutral
Every step from pH 0-14 is 0.1 times more
concentrated.
Look at figure 3.9 on pg 198 of your text to see
examples
How To Determine pH
The strength or conc. of acid determines
the extent that it reacts with H2O.
 You determine pH by:
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The reaction changes the conductivity of H2O
which can then be measured using a voltage
meter.
 Using pH paper – this paper changes to a
characteristic color with each specific pH then
the colors are matched to a chart
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Acid Rain
Carbon,nitrogen, & sulfur produced from
the burning of organic materials (contain
carbon) when they react with moisture in
the air to form acids.
 Acid rain occurs when these compounds
are washed out of the air by rain/snow.
 Acid rain doesn’t look, taste or feel
different
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What does acid rain do?
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Damages/destroys aquatic ecosystems (lakes &
streams)
Reduces productivity of crops
Harms other vegetation
Increase the decay of buildings, structures and
monuments.
Acid in soil dissolves mineral nutrients and allows them
to be washed away resulting in nutrient poor soil and
poor growing cond. (leaching)
Leaching may also release heavy metals (mercury, lead,
nickel) into water supplies where they are consumed by
plants and animals.
How to control acid rain
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By acid/base neutralization
As a result of the ice age the glaciers moved across
north america and deposited lots of calcium carbonate.
This basic substance neutralizes the acid rain and
therefore protects our lakes and streams.
So you add calcium carbonate to an acidic lake and you
neutralize the H2O (this process is called liming)
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The problem with this: once all the calcium carbonate is gone,
the pH of the lake will plummet and thus negatively affect
animals and plants by killing them.
Liming is very expensive
So we must try reduce or eliminate oxides in the air before they
get there.
Catalytic Converters
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These are the first step to reducing the oxides in
the air leading to acid rain.
These are required on all vehicles.
They contain ceramic or honeycomb structure
coated with a catalyst.
Remember a catalyst speeds up a reaction
without being used up in the reaction.
The converter aids the formation of CO2 and
H2O from hydrocarbons which reduces the amt
of CO and NO produced.
The converter encourages complete oxidation.
Pollution & Pollutants
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Pollutant – is any material or form of energy that
will cause harm to a living organism. Basically,
anything that will threaten the health or survival
of that organism.
Pollution – any alteration of the environment
producing a condition harmful to living things.
Eg. DDT pollution
To find out if pollution is occurring you need to
test on a living thing. Ie: indicator species.
Toxicity
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The ability of a chemical to cause harm to an organism.
Acute toxicity – serious symptoms occur with one
exposure.
Chronic toxicity- symptoms occur after an accumulation
of a chemical to a specific level. Ie: lead, alcohol
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The amt of chemical causing damage matters but can be very
hard to determine. This is because of many factors ( mass,
metabolism, gender)
Lethal Dose 50 is the amount of a substance that will kill
50% of the population.
Evaluate the risk of certain chemicals Pg.219-221