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Acidity and pH LESSON # 6

- e - e - e - e - e - e - e - e - e - e Na Chloride ion (Cl ) - Sodium ion (Na ) e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e Cl e - Sodium Chloride pH

- e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e Cl 17 - pH + 1 p 0 n + H

- e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e Cl 17 - Hydrogen Proton + Chloride anion - Hydrochloric Acid (HCl) pH + 1 p 0 n + H

Cl _ Na + Salt Cl _ H + Acid Hydrogen proton An acid is a substance that yields hydrogen protons when put in aqueous solution Cl _ Na + + Cl _ H + +

pH H H Cl Acidity

NeutralAcidicBasic Pure waterLemon juice Oven cleaner H + H + H + H + H + H + OH H + Hydrogen proton OH - Hydroxyl group It makes substances acidic It makes substances basic

A C I D: ACID It is a substance that yields hydrogen protons when put in aqueous solution (proton donor) pH H + H + H + H + H + H + H + H + H + H + H + H + H + H + H + ACIDIC WATER BECOMES ACIDIC H +

BASE BASE : It is a substance that accepts hydrogen ions when put in aqueous solution (proton acceptor) pH OH WATER BECOMES BASIC BASIC

Most bases accept hydrogen protons because they yield hydroxide groups, which combine with hydrogen to form water molecules + - OH + H H O 2 BASE OH It is a substance that accepts hydrogen ions when put in aqueous solution (proton acceptor)BASE:

H + H + H + H + H + H + H + H + H + H + H + H + H + H + H +H + H + H + pH A c i d i t y i n c r e a s e s The grade of acidity is proportional to the concentration of hydrogen protons H +

pH scale The pH scale Allows us to Quantify How Acidic or Basic Compounds are The pH is a scale used to quantified the level of acidity or concentration of hydrogen ions + HIs the pH = ? It is not H pH = + - log pH How the acidity is quantified?

H pH = + - log When the concentration of H increases, the pH decreases + When the concentration of H decreases, the pH increases + H + Acidity pH and H + Acidity pH and

AcidicBasic Lemon juice Baking soda H + H + H + H + H + H + OH H + H + High Acidity High pH Low Acidity pH Low High

pH Acidic Basic Neutral H + H + Lower Higher

When a solution becomes more acid, its pH drops When a solution becomes more basic, its pH rises Ex: Solution 1 is more acid than solution 2. Therefore, pH of solution 1 is _________ than pH of solution 2 Ex: Solution 3 is less acid than solution 4. Therefore, pH of solution 3 is _________ than pH of solution 4 Ex: Solution 5 is more basic than solution 6. Therefore, pH of solution 5 is _________ than pH of solution 6 Ex: Solution 7 is less basic than solution 8. Therefore, pH of solution 7 is _________ than pH of solution 8 pH

H pH = + - log Solution 1 is ____ times more acid than solution 2 Solution 1 is ____ times more acid than solution 3 Solution 1 pH: 7 Solution 2 pH: 8 Solution 3 pH: 9 pH

H + H + H + H + H + H + H + H + H + H + H + H + H + H + H +H + H + H + pH: ___ Solution 1Solution 2Solution 3Solution 4 When a solution becomes more acid, its pH drops 6543 When a solution becomes more basic, its pH raises M o r e a c i d M o r e b a s i c pH

Acidic Basic H + H + Higher Lower pH

pH Acidic Basic H + H + Higher Lower pH

pH H + H + Higher Lower pH Does not change

pH

How the pH is measured ? pH

Why does pH matter ? Because living things are very sensitive to changes in the pH. Ex: The pH of human blood normally ranges from If pH drops under 7.35 the persons has an acidosis. If the pH raises over 7.45 the person is in alkalosis. pH below 7 can produce coma and death pH above 7.8 can produce uncontrollable and sustained skeletal muscle contraction and death pH

Abnormal fluctuations in pH can damage cells and tissues by: 1- Breaking chemicals bounds 2- Changing the shape of proteins, which consequently lose their functions. 3- Altering cellular functions pH

Buffers resist changes in pH because they can remove or release hydrogen ions If the concentration of H buffer system remove H and the pH does not change + + If the concentration of H buffer system releases H and the pH does not change + + Buffer is a chemical system that resists abrupt and large swings in the pH of body fluids Homeostasis of acid-base balance is carefully regulated by chemical systems called buffers

pH H + OH -WATER pH H + Does not change OH - pH Does not change Buffering Solutions