Acids & BasesAcids & Bases

pH scalepH scale

Ranges from 0-14Ranges from 0-14 0 – 6 = Acid 0 – 6 = Acid

0 is most acidic0 is most acidic Concentration of HConcentration of H++ (hydrogen or hydronium) ions is (hydrogen or hydronium) ions is

higher than OHhigher than OH-- (hydroxide) ions (hydroxide) ions 8 – 14 = Base8 – 14 = Base

14 is most basic14 is most basic Concentration of OHConcentration of OH-- (hydroxide) ions is higher than (hydroxide) ions is higher than

HH++ (hydrogen) ions (hydrogen) ions 7 = neutral 7 = neutral

Concentration of HConcentration of H++ (hydrogen) ions and OH (hydrogen) ions and OH-- (hydroxide) ions are equal (hydroxide) ions are equal

pH scalepH scale

Each increase / decrease of 1 on the Each increase / decrease of 1 on the pH scale (Ex. 1 to 2) represents a 10 pH scale (Ex. 1 to 2) represents a 10 fold increase / decrease of ion fold increase / decrease of ion concentration change.concentration change.Ex. Moving from 2 to 4 on the pH scale Ex. Moving from 2 to 4 on the pH scale

DECREASES the HDECREASES the H+ + ion concentration (or ion concentration (or INCREASES OHINCREASES OH-- concentration) by 100 concentration) by 100 times. (10 X 10)times. (10 X 10)How much does the OHHow much does the OH-- concentration change concentration change

when moving from 10 to 7 on the pH scale?when moving from 10 to 7 on the pH scale?

Calculating pH from H+ Calculating pH from H+ concentrationconcentration

pH = - (log [HpH = - (log [H++])])Ex. The hydrogen ion concentration Ex. The hydrogen ion concentration

of a solution is 6.3 x 10of a solution is 6.3 x 10-8-8. What is the . What is the pH of this solution?pH of this solution?

AcidsAcidsHave a higher concentration of HHave a higher concentration of H++

(hydrogen) ions(hydrogen) ionspH of 0-6pH of 0-6Taste sourTaste sourFeel like water, but “sting” the skinFeel like water, but “sting” the skinLemon juice, stomach acid, vinegarLemon juice, stomach acid, vinegarLitmus paper: blue Litmus paper: blue red redPhenolphthalein indicator remains Phenolphthalein indicator remains

colorlesscolorlessReacts with metals and carbonatesReacts with metals and carbonates

BasesBasesHave a higher concentration of OHHave a higher concentration of OH--

(hydroxide) ions(hydroxide) ionspH of 8-14pH of 8-14Taste bitterTaste bitterFeel slipperyFeel slipperyCleaners, soap, baking sodaCleaners, soap, baking sodaLitmus paper red Litmus paper red blue bluePhenolphthalein indicator turns pinkPhenolphthalein indicator turns pinkDo NOT react with metals and Do NOT react with metals and

carbonatescarbonates

Neutral solutionsNeutral solutions

Have an equal concentration of HHave an equal concentration of H++ (hydrogen) and OH(hydrogen) and OH-- (hydroxide) ions (hydroxide) ions

Milk, pure water, bloodMilk, pure water, bloodLitmus paper: no changeLitmus paper: no changepH of 7pH of 7Non reactiveNon reactive

Strong Acids & BasesStrong Acids & Bases

Dissociate fully into their ionsDissociate fully into their ionsAcids break down to H+Acids break down to H+Bases break down to OH-Bases break down to OH-

Conduct electrical current well Conduct electrical current well (strong electrolyte)(strong electrolyte)

ExamplesExamples Strong acid: hydrochloric acidStrong acid: hydrochloric acid

Weak acid: acetic acidWeak acid: acetic acid Strong base: sodium hydroxideStrong base: sodium hydroxide

Weak base: ammonium hydroxideWeak base: ammonium hydroxide

BufferBuffer

Keeps pH at neutral range (resists Keeps pH at neutral range (resists changes in pH) changes in pH)

Buffers are a combination of a weak Buffers are a combination of a weak acid and its conjugate base. acid and its conjugate base.

The weak acid can react with added The weak acid can react with added base The weak base can reacts with base The weak base can reacts with added acid added acid

Buffer ContinuedBuffer Continued

Ex.Ex. CO2 transport provides buffering system for the blood in

that CO2 combines with Water to form carbonic acid (HH22COCO33)and then bicarbonate (HCO33

−−).).

IndicatorsIndicators

Indicators contain certain dyes which Indicators contain certain dyes which change color at various pH values change color at various pH values (used to read pH). (used to read pH). Red & Blue Litmus paperRed & Blue Litmus paperpH paperpH paperPhenolphthalein indicator solutionPhenolphthalein indicator solutionUniversal indicator solutionUniversal indicator solution

WarningWarning

All of the acids and bases used in this All of the acids and bases used in this class are corrosive to the eyes & class are corrosive to the eyes & skin. They are TOXIC by ingestion & skin. They are TOXIC by ingestion & direct inhalation. Avoid breathing the direct inhalation. Avoid breathing the vapors & wear safety goggles at all vapors & wear safety goggles at all times. times.