Acids, Bases, and pH

Essential Question Explain the differences between acids and bases and give examples of each.

What is pH?  Scale based on concentration of H + ions in solution  ACIDIC is  BASIC is  NEUTRAL is 7

l chemicals that release H + ions in a solution. l So…acids produce more H + ions (lower pH). l Low pH means high H + ion concentration l What are acids?

l Low pH – 0 to 7 l Sour taste l Turns litmus paper red l Corrosive l Reacts with metals l Electrolytes l Properties of Acids

l chemicals that release OH - ions in a solution. l So…bases produce more OH - ions and less H + ions (higher pH) l What are bases? Soap

l High pH – 7 to 14 l Bitter taste l Feels slippery l Turns litmus blue l Corrosive l Reacts with fats l Properties of Bases

l Acids (low pH) l Bases (high pH) l used throughout industry… fertilizer, soft drinks, batteries, etching metals & glass. l unclog drains; used as cleaners, soaps, shampoos.

l pH [OH - ] l pH >7 means [H + ] 7 means [H + ] < [OH - ] l pH = 7 means [H + ] = [OH - ] l How do these pH values compare?

l pH of drinking water indicates its quality. –pH too high, pipes clog –pH too low, pipes corrode l Why is pH important?

l pH of natural bodies of water has to be right (pH 6-8) for fish and other aquatic animals and plants to reproduce. –Lower pH and they die! l pH plays important role in digestion. l pH important to life

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Electrolytes PAGE 99

l dissociate (break apart into ions) almost completely in water. l do not dissociate (ionize) completely in water. l Strong acids & bases l Weak acids & bases

l Concentrated l Dilute l little water in the solution and lots of acid / base molecules. l lots of water in the solution and few acid / base molecules.

l Mixing equal parts of an acid and base together, results in a solution made of water and a salt. l It is neutral – (pH = 7, [H + ] = [OH - ]) l They neutralize each other! l What happens when you mix an acid and a base?

Examples: HCl + NaOH  NaCl + H 2 O strong acid + strong base  salt + water H 2 SO 4 + 2KOH  K 2 SO 4 + 2H 2 O

l All acids and bases are electrolytes because they form ions when dissolved. l Electrolytes – ions which allow a solution to conduct electricity when dissolved in water. l Electrolytes

l Chemicals that do not form ions when they are dissolved in solution. l Example: sugar in water l Non- electrolytes

l Any rain, snow, hail, sleet, fog with pH < 5.6 l Harmful to plants, animals, people, buildings l What is acid rain?

l Acid rain results from gases produced during combustion reactions. –SO 2 from coal burning –SO 3 and NO 2 from rxns with oxygen- containing compounds in atmosphere –NO from traffic & power plants l Gases produced from acid rain?

These sulfur and nitrogen gases mix with water to form sulfuric and nitric acid. SO 3 + H 2 O  H 2 SO 4 air pollutant rain acid rain

Dissolves poisonous metals in soil

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