Environmental Chemistry 2Environmental Chemistry 2

Acids & BasesAcids & BasesPg.197Pg.197

Acids & bases are used everyday and Acids & bases are used everyday and within our bodies.within our bodies.

They are used for distinct roles & tastes.They are used for distinct roles & tastes.Eg. HCL is used in your stomach for digestion Eg. HCL is used in your stomach for digestion

(very strong acid)(very strong acid)Phosphoric acid is used in carbonated drinks Phosphoric acid is used in carbonated drinks

as a flavoring agent and gives food a tangy as a flavoring agent and gives food a tangy flavor. (like cheese, jams, jelly)flavor. (like cheese, jams, jelly)

Identifying Acids & BasesIdentifying Acids & Bases You can identify acids & You can identify acids &

bases by:bases by: Taste Taste

**not useful if unknownnot useful if unknown TouchTouch*not useful if unknown*not useful if unknown Chemical indicator Chemical indicator

litmus (mixture of plant litmus (mixture of plant compounds extracted from compounds extracted from lichens)lichens)

Litmus turns red Litmus turns red acid acid blue blue base base

Usually called litmus paperUsually called litmus paper

AcidAcid BaseBase

Taste sourTaste sour

Eg. lemonsEg. lemons

Taste bitterTaste bitter

Eg. Eg. Celery,horse Celery,horse radishradish

Litmus redLitmus red Slippery/greasySlippery/greasy

Litmus - blueLitmus - blue

pH ScalepH Scale

pH – strength of hydrogenpH – strength of hydrogen pH is the strength of an acid or basepH is the strength of an acid or base pH <7 is an acidpH <7 is an acid pH>7 is a basepH>7 is a base pH of 7 is neutralpH of 7 is neutral Every step from pH 0-14 is 0.1 times more Every step from pH 0-14 is 0.1 times more

concentrated.concentrated. Look at figure 3.9 on pg 198 of your text to see Look at figure 3.9 on pg 198 of your text to see

examplesexamples

How To Determine pHHow To Determine pH

The strength or conc. of acid determines The strength or conc. of acid determines the extent that it reacts with H2O.the extent that it reacts with H2O.

You determine pH by:You determine pH by:The reaction changes the conductivity of H2O The reaction changes the conductivity of H2O

which can then be measured which can then be measured using a voltage using a voltage meter.meter.

Using pH paper – this paper changes to a Using pH paper – this paper changes to a characteristic color with each specific pH then characteristic color with each specific pH then the colors are matched to a chartthe colors are matched to a chart

Acid RainAcid Rain

Carbon,nitrogen, & sulfur produced from Carbon,nitrogen, & sulfur produced from the burning of organic materials (contain the burning of organic materials (contain carbon) when they react with moisture in carbon) when they react with moisture in the air to form acids.the air to form acids.

Acid rain occurs when these compounds Acid rain occurs when these compounds are washed out of the air by rain/snow. are washed out of the air by rain/snow.

Acid rain doesn’t look, taste or feel Acid rain doesn’t look, taste or feel differentdifferent

What does acid rain do?What does acid rain do? Damages/destroys aquatic ecosystems (lakes & Damages/destroys aquatic ecosystems (lakes &

streams)streams) Reduces productivity of cropsReduces productivity of crops Harms other vegetationHarms other vegetation Increase the decay of buildings, structures and Increase the decay of buildings, structures and

monuments.monuments. Acid in soil dissolves mineral nutrients and allows them Acid in soil dissolves mineral nutrients and allows them

to be washed away resulting in nutrient poor soil and to be washed away resulting in nutrient poor soil and poor growing cond. (leaching)poor growing cond. (leaching)

Leaching may also release heavy metals (mercury, lead, Leaching may also release heavy metals (mercury, lead, nickel) into water supplies where they are consumed by nickel) into water supplies where they are consumed by plants and animals.plants and animals.

How to control acid rainHow to control acid rain By acid/base neutralizationBy acid/base neutralization As a result of the ice age the glaciers moved across As a result of the ice age the glaciers moved across

north america and deposited lots of calcium carbonate. north america and deposited lots of calcium carbonate. This basic substance neutralizes the acid rain and This basic substance neutralizes the acid rain and therefore protects our lakes and streams.therefore protects our lakes and streams.

So you add calcium carbonate to an acidic lake and you So you add calcium carbonate to an acidic lake and you neutralize the H2O (this process is called liming)neutralize the H2O (this process is called liming) The problem with this: once all the calcium carbonate is gone, The problem with this: once all the calcium carbonate is gone,

the pH of the lake will plummet and thus negatively affect the pH of the lake will plummet and thus negatively affect animals and plants by killing them.animals and plants by killing them.

Liming is very expensiveLiming is very expensive So we must try reduce or eliminate oxides in the air before they So we must try reduce or eliminate oxides in the air before they

get there.get there.

Catalytic ConvertersCatalytic Converters These are the first step to reducing the oxides in These are the first step to reducing the oxides in

the air leading to acid rain.the air leading to acid rain. These are required on all vehicles.These are required on all vehicles. They contain ceramic or honeycomb structure They contain ceramic or honeycomb structure

coated with a catalyst.coated with a catalyst. Remember a catalyst speeds up a reaction Remember a catalyst speeds up a reaction

without being used up in the reaction.without being used up in the reaction. The converter aids the formation of CO2 and The converter aids the formation of CO2 and

H2O from hydrocarbons which reduces the amt H2O from hydrocarbons which reduces the amt of CO and NO produced.of CO and NO produced.

The converter encourages complete oxidation.The converter encourages complete oxidation.

Pollution & PollutantsPollution & Pollutants

Pollutant – is any material or form of energy that Pollutant – is any material or form of energy that will cause harm to a living organism. Basically, will cause harm to a living organism. Basically, anything that will threaten the health or survival anything that will threaten the health or survival of that organism.of that organism.

Pollution – any alteration of the environment Pollution – any alteration of the environment producing a condition harmful to living things. producing a condition harmful to living things. Eg. DDT pollutionEg. DDT pollution

To find out if pollution is occurring you need to To find out if pollution is occurring you need to test on a living thing. Ie: indicator species.test on a living thing. Ie: indicator species.

ToxicityToxicity The ability of a chemical to cause harm to an organism.The ability of a chemical to cause harm to an organism. Acute toxicity – serious symptoms occur with one Acute toxicity – serious symptoms occur with one

exposure.exposure. Chronic toxicity- symptoms occur after an accumulation Chronic toxicity- symptoms occur after an accumulation

of a chemical to a specific level. Ie: lead, alcoholof a chemical to a specific level. Ie: lead, alcohol The amt of chemical causing damage matters but can be very The amt of chemical causing damage matters but can be very

hard to determine. This is because of many factors ( mass, hard to determine. This is because of many factors ( mass, metabolism, gender)metabolism, gender)

Lethal Dose 50 is the amount of a substance that will kill Lethal Dose 50 is the amount of a substance that will kill 50% of the population.50% of the population.

Evaluate the risk of certain chemicals Pg.219-221Evaluate the risk of certain chemicals Pg.219-221