Acids & Bases

Acids Arrhenius Model Produce hydrogen ions aqueous solution. HCl  H + (aq) + Cl - (aq) Acids you SHOULD know: Acids you SHOULD know: Strong Acids Hydrochloric acid, HCl Nitric acid, HNO 3 Sulfuric acid, H 2 SO 4 Weak Acids Phosphoric acid, H 3 PO 4 Acetic acid, HC 2 H 3 O 2

Properties of Acids A cids taste sour A cids affect indicators B lue litmus turns red M ethyl orange turns red A cids have a pH lower than 7 A cids are proton (hydrogen ion, H + ) donors A cids react with active metals, produce H 2 A cids react with carbonates A cids neutralize bases

Bases Arrhenius Model Produce Hydroxide ions. NaOH  Na + (aq) + OH - (aq) Examples of Bases Examples of Bases Sodium hydroxide (lye), NaOH Sodium hydroxide (lye), NaOH Potassium hydroxide, KOH Potassium hydroxide, KOH Magnesium hydroxide, Mg(OH) 2 Magnesium hydroxide, Mg(OH) 2 Calcium hydroxide (lime), Ca(OH) 2 Calcium hydroxide (lime), Ca(OH) 2

Properties of Bases Bases taste bitter Bases affect indicators Red litmus turns blue Phenolphthalein turns purple Bases have a pH greater than 7 Bases are proton (hydrogen ion, H + ) acceptors Solutions of bases feel slippery Bases neutralize acids

Bronsted – Lowery Model ACID: Substance that can donate proton (H +1 ). BASE: Substance that can accept proton (must contain lone pair of electrons).

The pH Scale The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. The pH scale is logarithmic and as a result, each whole pH value below 7 is ten times more acidic than the next higher value. For example, pH 4 is ten times more acidic than pH 5 and 100 times (10 times 10) more acidic than pH 6. The same holds true for pH values above 7, each of which is ten times more alkaline (another way to say basic) than the next lower whole value.

The pH Scale The pH scale is logarithmic and as a result, each whole pH value below 7 is ten times more acidic than the next higher value. For example, pH 4 is ten times more acidic than pH 5 and 100 times (10 times 10) more acidic than pH 6. The same holds true for pH values above 7, each of which is ten times more alkaline (another way to say basic) than the next lower whole value.

Calculating pH or pOH pH = -log[H + ] Example [H + ] = 1.0 x Answer pH=9.0 pOH = -log[OH + ] Example [OH + ] = 1.0 x Answer pOH = 6 pOH + pH = 14.0

Acids Neutralize Bases HCl + NaOH  NaCl + H 2 O Neutralization reactions ALWAYS produce a salt and water. H 2 SO 4 + 2NaOH  Na 2 SO 4 + 2H 2 O 2HNO 3 + Mg(OH) 2  Mg(NO 3 ) 2 + 2H 2 O

Bases Neutralize Acids Milk of Magnesia contains magnesium hydroxide, Mg(OH) 2, which neutralizes stomach acid, HCl. 2 HCl + Mg(OH) 2 MgCl H 2 O

Acid Base Titration Titration a method for determining the concentration of a solution by reacting a known volume of that solution with a solution of known concentration. In a titration procedure, a measured volume of an acid or base of unknown concentration is placed in a beaker or flask, and initial pH recorded.

Titration with an Indicator 15