# Acids & Bases. pH scale Ranges from 1-14 Ranges from 1-14 1 – 6 = Acid 1 – 6 = Acid 1 is most acidic 1 is most acidic Concentration of H + (hydrogen)

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Acids & Bases

pH scale Ranges from 1-14 Ranges from 1-14 1 – 6 = Acid 1 – 6 = Acid 1 is most acidic 1 is most acidic Concentration of H + (hydrogen) ions is higher than OH - (hydroxide) ions Concentration of H + (hydrogen) ions is higher than OH - (hydroxide) ions 8 – 14 = Base 8 – 14 = Base 14 is most basic 14 is most basic Concentration of OH - (hydroxide) ions is higher than H + (hydrogen) ions Concentration of OH - (hydroxide) ions is higher than H + (hydrogen) ions 7 = neutral 7 = neutral Concentration of H + (hydrogen) ions and OH - (hydroxide) ions are equal Concentration of H + (hydrogen) ions and OH - (hydroxide) ions are equal

pH scale Each increase / decrease of 1 on the pH scale (Ex. 1 to 2) represents a 10 fold increase / decrease of ion concentration change. Each increase / decrease of 1 on the pH scale (Ex. 1 to 2) represents a 10 fold increase / decrease of ion concentration change. Ex. Moving from 2 to 4 on the pH scale DECREASES the H + ion concentration (or INCREASES OH - concentration) by 100 times. (10 X 10) Ex. Moving from 2 to 4 on the pH scale DECREASES the H + ion concentration (or INCREASES OH - concentration) by 100 times. (10 X 10) How much does the OH - concentration change when moving from 10 to 7 on the pH scale? How much does the OH - concentration change when moving from 10 to 7 on the pH scale?

Acids Have a higher concentration of H + (hydrogen) ions Have a higher concentration of H + (hydrogen) ions pH of 1-6 pH of 1-6 Taste sour Taste sour Feel like water, but “sting” the skin Feel like water, but “sting” the skin Lemon juice, stomach acid, vinegar Lemon juice, stomach acid, vinegar Litmus paper: blue  red Litmus paper: blue  red Phenolphthalein indicator remains colorless Phenolphthalein indicator remains colorless Reacts with metals and carbonates Reacts with metals and carbonates

Bases Have a higher concentration of OH - (hydroxide) ions Have a higher concentration of OH - (hydroxide) ions pH of 8-14 pH of 8-14 Taste bitter Taste bitter Feel slippery Feel slippery Cleaners, soap, baking soda Cleaners, soap, baking soda Litmus paper red  blue Litmus paper red  blue Phenolphthalein indicator turns pink Phenolphthalein indicator turns pink Do NOT react with metals and carbonates Do NOT react with metals and carbonates

Neutral solutions Have an equal concentration of H + (hydrogen) and OH - (hydroxide) ions Have an equal concentration of H + (hydrogen) and OH - (hydroxide) ions Milk, pure water, blood Milk, pure water, blood Litmus paper: no change Litmus paper: no change pH of 7 pH of 7 Non reactive Non reactive

Strong Acids & Bases Dissociate fully into their ions Dissociate fully into their ions Acids 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)Examples Strong acid: hydrochloric acid Strong acid: hydrochloric acid Weak acid: acetic acid Weak acid: acetic acid Strong base: sodium hydroxide Strong base: sodium hydroxide Weak base: ammonium hydroxide Weak base: ammonium hydroxide

Buffer Keeps pH at neutral range (resists changes in pH) Keeps pH at neutral range (resists changes in pH) Made with weak acids and weak bases Made with weak acids and weak bases The weak acid can react with added base The weak base can reacts with added acid The weak acid can react with added base The weak base can reacts with added acid

Indicators Indicators contain certain dyes which change color at various pH values (used to read pH). Indicators contain certain dyes which change color at various pH values (used to read pH). Red & Blue Litmus paper Red & Blue Litmus paper pH paper pH paper Phenolphthalein indicator solution Phenolphthalein indicator solution Universal indicator solution Universal indicator solution

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

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