# What is pH? Tells us the relative quantity of H + ions (or the acidity) in solution. Tells us the relative quantity of H + ions (or the acidity) in solution.

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What is pH? Tells us the relative quantity of H + ions (or the acidity) in solution. Tells us the relative quantity of H + ions (or the acidity) in solution. The greater the [H + ] the lower the pH. The greater the [H + ] the lower the pH.

pH Values of Common Liquids

H + and OH - in Pure Water Self Ionization of Water: small quantity of water molecules in a sample will self ionize. Results in small, but equal [H + ] and [OH - ] Concentration of these ions is 1 x 10 -7 M (pH = 7) Reversible reaction that is at equilibrium. H 2 O H + + OH - H 2 O H + + OH - [H + ] = [OH - ] [H + ] = [OH - ] H+H+ OH - http://youtu.be/kW-Zk4zABzw

When Acid is Added to Water Increases the H + concentration Increases the H + concentration As H + increases, OH - decreases As H + increases, OH - decreases [H + ] > [OH - ] H+H+ OH -

When Base is Added to Water Increases OH - concentration Increases OH - concentration When OH - increases, H + decreases When OH - increases, H + decreases [OH  ] > [H + ] H+H+ OH -

pH Scale 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Neutral [H + ] > [OH - ] [H + ] = [OH - ] [OH - ] > [H + ] Acidic Basic

Important Summary Acidic:[H+] > [OH-] Acidic:[H+] > [OH-] Basic:[H+] < [OH-] Basic:[H+] < [OH-] Neutral:[H+] = [OH-] Neutral:[H+] = [OH-]

Pretty Hydrangeas The color of hydrangea flowers depends on the pH of the soil. The color of hydrangea flowers depends on the pH of the soil.

Calculating pH pH = - log [H + ] From the French pouvoir hydrogene From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen) (“hydrogen power” or power of hydrogen)

11 [H + ] pH 1 x 10 -5 M 5 1 x 10 -9 M 9 1 x 10 -11 M 11

If the [H+] is 0.000001 M, what is the pH? If the [H+] is 0.000001 M, what is the pH? pH = 6 If the [H+] is 0.01M, what is the pH? If the [H+] is 0.01M, what is the pH? pH = 2

If the pH is 10, what is the [H+]? If the pH is 10, what is the [H+]? [H+] = 1 x 10 -10 M If the pH is 4, what is the [H+]? If the pH is 4, what is the [H+]? [H+] = 1 x 10 -4 M

Calculating pOH What if you are given the concentration of a base? What if you are given the concentration of a base? Ex:.000001M LiOH Ex:.000001M LiOH You need to find the pOH!!

pOH pOH = -log [OH - ] Ex:.000001M LiOH = 1 x 10 -6 pOH = 6 Ex:.0001M NaOH = 1 x 10 -4 pOH = 4

How can you find pH of a Base? Easy!!! Easy!!! pH + pOH = 14 Ex:.000001M LiOH = 1 x 10 -6 pOH = 6 pH = 8 Ex:.0001M NaOH = 1 x 10 -4 pOH = 4 pH = 10

Kw or Equilibrium Constant for Water If you know the concentration of one ion you can find the other! [H+] x [OH-] = 1 x 10 -14 If [H+] is.001M what is the [OH-]? If [H+] is.001M what is the [OH-]? [1 x 10 -3 ] x [OH-] = 1 x 10 -14 [OH-] = 1 x 10 -11

Everything keeps adding up to 14!! What’s up with that?

Let’s Try It You have a.001 HCl solution. Find: [H+], [OH-], pH, pOH

Let’s Try It You have a.000000001M NaOH solution. Find: [H+], [OH-], pH, pOH

Equation Summary pH = -log [H + ]pOH = -log [OH - ] [H + ] = 10 -pH [OH - ] = 10 -pOH pH + pOH = 14[H + ] x [OH - ] = 1x10 -14 Acidic solution: pH 7 Neutral solution: pH = 7pOH = 7 Basic solution: pH > 7pOH 7pOH < 7

Let’s Practice A solution with a pH of 2.0 has a hydronium ion concentration ten times greater than a solution with a pH of A solution with a pH of 2.0 has a hydronium ion concentration ten times greater than a solution with a pH of (1) 1 (1) 1 (2) 3 (3) 0.20 (3) 0.20 (4) 20

Which statement correctly describes a solution with a pH of 9? Which statement correctly describes a solution with a pH of 9? (1) It has a higher concentration of H 3 O + than OH – and causes litmus to turn blue. (2) It has a higher concentration of OH – than H 3 O + and causes litmus to turn blue. (3) It has a higher concentration of H 3 O + than OH – and causes methyl orange to turn yellow. (4) It has a higher concentration of OH – than H 3 O + and causes methyl orange to turn red.

What is the pH of a solution that has a hydronium ion concentration 100 times greater than a solution with a pH of 4? What is the pH of a solution that has a hydronium ion concentration 100 times greater than a solution with a pH of 4? (1) 5 (2) 3 (3) 2 (3) 2 (4) 6

Solution A has a pH of 3 and solution Z has a pH of 6. Solution A has a pH of 3 and solution Z has a pH of 6. How many times greater is the hydronium ion concentration in solution A than the hydronium ion concentration in solution Z? (1) 100 (2) 3 (3) 2 (3) 2 (4) 1000

When the pH of a solution changes from a pH of 5 to a pH of 3, the hydronium ion concentration is When the pH of a solution changes from a pH of 5 to a pH of 3, the hydronium ion concentration is 1). 0.01 of the original content 2). 0.1 of the original content 3). 10 times the original content 4). 100 times the original content

As the pH of a solution is changed from 3 to 6, the concentration of hydronium ions As the pH of a solution is changed from 3 to 6, the concentration of hydronium ions (1) increases by a factor of 3 (2) increases by a factor of 1000 (3) decreases by a factor of 3 (4) decreases by a factor of 1000

Honors Questions If the pH of a solution is 3.25 find the pOH, [H+], and [OH-]. If.065 mole of KOH is placed in 20 liters of water, what is the resulting pH?

Acid Rain (Not to be confused with “Chocolate Rain”)

Acid Rain Unpolluted rain has a pH of 5.6 Unpolluted rain has a pH of 5.6 It is naturally acidic due to the gases in the air that dissolve in it. It is naturally acidic due to the gases in the air that dissolve in it.

Acid Rain Rain with a pH below 5.6 is “acid rain“ Rain with a pH below 5.6 is “acid rain“

pH of Rainwater across United States in 2001

Sources of Acid Rain

Power stations Power stations Oil refineries Oil refineries Coal with high S content Coal with high S content Car and truck emissions Car and truck emissions Bacterial decomposition, and lightning hitting N 2 Bacterial decomposition, and lightning hitting N 2

CO 2 in the air forms carbonic acid CO 2 in the air forms carbonic acid CO 2 + H 2 O H 2 CO 3 This increases the [H + ] of rain This increases the [H + ] of rain H 2 CO 3 H + (aq) + HCO 3 -(aq) Reactions with oxygen in air form SO 3 Reactions with oxygen in air form SO 3 2SO 2 + O 2 2 SO 3 Reactions with water in air form acids Reactions with water in air form acids SO 3 + H 2 O H 2 SO 4 sulfuric acid NO + H 2 O HNO 2 nitrous acid HNO 2 + H 2 O HNO 3 nitric acid HNO 2 + H 2 O HNO 3 nitric acid

Effects of Acid Rain

Leaches heavy metals like Al from soil, which kills fish Leaches heavy metals like Al from soil, which kills fish Fish kills in spring from runoff due to accumulation of large amounts of acid in snow Fish kills in spring from runoff due to accumulation of large amounts of acid in snow Prevents shellfish from building strong shells Prevents shellfish from building strong shells Dissolves waxy coatings that protect leaves from bacteria Dissolves waxy coatings that protect leaves from bacteria Corrodes metals, textiles, paper and leather Corrodes metals, textiles, paper and leather

Honors: pH and pOH game Honors: pH and pOH game http://www.quia.com/rr/4051.html http://www.quia.com/rr/4051.html http://www.quia.com/rr/4051.html

Acid Rain Destroys National Monuments http://news.discovery.com/videos/earth-acid- rain-eating-washington-dc.html http://news.discovery.com/videos/earth-acid- rain-eating-washington-dc.html Global Warming: CO 2 and Ocean Acidity http://planetgreen.discovery.com/videos/blue -august-acid-in-the-water.html http://planetgreen.discovery.com/videos/blue -august-acid-in-the-water.html

Acid Rain Site produced by EPA Acid Rain Site produced by EPA http://www.epa.gov/acidrain/education/site _kids/ http://www.epa.gov/acidrain/education/site _kids/ http://www.epa.gov/acidrain/education/site _kids/ http://www.epa.gov/acidrain/education/site _kids/ EPA Website Detailing Acid Rain Causes and Effects as well as Legislation EPA Website Detailing Acid Rain Causes and Effects as well as Legislation http://www.epa.gov/acidrain/ http://www.epa.gov/acidrain/ http://www.epa.gov/acidrain/

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