1. What is it?2. What is the main cause of it?3. What chemical reactions are

involved?4. What are the effects of it?5. What can we do about it?

pH related to the exponent of molarity of [H3O

+]

Examples:Concentration of H3O

+ is 1.0 × 10–1 M pH =1

Concentration of H3O+ is 1.0 × 10–5 M pH =5

Concentration of H3O+ is 1.0 × 10–8 M pH =8

Every 1.0 drop in pH = ten times higher [H3O

+]

pH = 7.0 [H3O+] = 1/10,000,000 moles

per literpH = 6.0 [H3O

+] = 1/1,000,000 moles per literpH = 1.0 [H3O

+] = 1/10 moles per liter

[H3O+] at pH 1 is million X higher than at

pH 7

Review- pH Scale

pH Scale

pH of Selected natural liquids•Ocean water 8.0 – 8.2 (varies by location & time)•Human blood 7.35 – 7.45•Pure water 7.0

• At 25°C both [H3O+] and [OH–] is 1.0 × 10–7 M

•“Clean” rain 5.6 – 5.7•“Acid” rain is defined as anything with pH <5.0

Atmosphere behaves much like human blood. Both have CO2 gas which can dissolve in

water After dissolving, CO2 reacts with water

to form carbonic acid - a weak acid. CO2 + H2O H2CO3

Carbonic acid and bicarbonate ions form an important pH buffer

[H2CO3 + H2O HCO3- + H3O+] “Clean” rain typically has pH 5.6 - 5.7

About 15 times [H3O+] of pure water

Why “Clean” Rain is slightly acidic

Formed from anthropogenic sources (i.e. human activity)

SO2 gas - released primarily from burning coal

SO2 reacts with water through a series of reactions to form sulfuric acid – a strong acid.

SO2 + H2O H2SO4

NO2 gas - released primarily from internal combustion engines burning gasoline and diesel fuel

NO2 reacts with water to form nitric acid (a strong acid) and nitrous acid (a weak acid)

2NO2 + H2O HNO3 + HNO2

Causes of “Acid Rain”

Forests, freshwaters and soils become more acidicTrees lose nutrients, poisoned, susceptible

to attack by insects, fungus, etc. Insect and aquatic life-forms (especially

fish) struggle and dieSome lakes in New England had no non-algae

life in mid-80’s

Manmade structures are also impactedDamage to buildings and sculptures made

of stone

Adverse Impacts of “Acid Rain”

“Acid” rain pH < 5.0•Typically 5 - 20 times [H3O+] of “normal” rain with pH = 5.7

Acid Rain video clip made by students:http://www.youtube.com/watch?v=893KB3s_jIA&feature=related

Trees killed by acid rain

GNU Free Documentation License

Video clip - What’s

eating Washington D.C http://www.youtube.com/watch?v=MqHw1hMEkAQ&feature=fvst

Acid rain can eat through stone and metal. Accelerated weathering process on stone angel's face.

Photographer: Michael Drager | Agency: Dreamstime.com

Coal Combustion & Acid Rain

2007-03-01 03:49 Analogue Kid 2048×1536×8 (868607 bytes) The General James M. Gavin plant on the Ohio River. Note the clouds of water and Sulfuric Acid coming from the stacks (the emissions from the Cooling Towers are just water vapor). Self made photo.

Video Clip about Cleaning Up Coal

Technologyhttp://www.youtube.com/watch?v=HE6Y0iEuXMQ&feature=fvwrel

How to Stop Acid RainTighter emissions regulation for power

generationCapture more SO2 and other pollutantsUse alternative energy sources

Transportation improvementsCatalytic converters to reduce NO2

Hybrids and alternative power sourcesImproved mpg standards

1. What is it?2. What is the main cause of it?3. What chemical reactions are

involved?4. What are the effects of it?5. What can we do about it?