 # PH and pOH Chem 332 – ODette. pH (Potential of Hydrogen) Measures the degree of acidity or basicity of an aqueous solution Corresponds to the hydrogen.

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pH and pOH Chem 332 – ODette

pH (Potential of Hydrogen) Measures the degree of acidity or basicity of an aqueous solution Corresponds to the hydrogen ion concentration, [H + ] Measured on a scale from 0-14 - pH < 7 Acid - pH 7 Neutral - pH > 7 Base

pH of Different Solutions Bases: -Bleach = 13 -Soapy Water = 12 -Ammonia Solution = 11 -Milk of Magnesia = 10 -Baking Soda = 9 -Sea Water = 8 Acids: -Urine = 6 -Black Coffee = 5 -Tomato Juice = 4 -Orange Juice = 3 -Lemon Juice = 2 -Gastric Acid =1 Neutral: - Distilled Water = 7

Acid Dissociation Dissociation = acid or base separates into ions in water Ex: HBr (aq) H + (aq) + Br - (aq)

Calculating pH Based on a log scale From [H + ] pH From pH [H + ] [H + ] = 10 -pH pH = - log [H + ] Memorize

Step-Through Example Find pH of 0.01 M of Hydrochloric Acid HCl(aq) H + (aq) + Cl - (aq) 1 mole 1 mole 1 mole [0.01 M] [0.01 M] + [0.01 M] pH = - log [H + ] = - log [0.01M] pH = 2

pOH (Potential of Hydroxide) Similar to pH except pOH measures the hydroxide ion concentration, [OH - ] Base Dissociation Ex: KOH (aq) K + (aq) + OH - (aq)

Calculating pOH From [OH - ] pOH From pOH [OH - ] [OH - ] = 10 -pOH pOH = - log [OH - ] Memorize

Relationship between pH and pOH pH + pOH = 14 [H + ] x [OH - ] = 1 x 10 -14 Memorize

Ex: Find the pH of 0.1 M of Nitric Acid, HNO 3 HNO 3 H + + NO 3 - 1 mole 1 mole 1 mole [0.1 M] [0.1 M] + [0.1 M] pH = - log [H + ] = - log [0.1M] pH = 1

Ex: Find the pH of 0.005 M of Calcium Hydroxide, Ca(OH) 2 Ca(OH) 2 Ca + + 2OH - 1 mole 1 mole 2 moles [0.005 M] [0.005 M] + [0.01 M] pOH = - log [OH - ] = - log [0.01M] pOH = 2 pH = 14 – pOH = 14 - 2 pH = 12

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