Acids, Bases and Salts

● Acids

○ A substance which turns blue litmus paper red

○ It has a sour taste and is corrosive

○ Reacts with a base to form salt

○ Disassociates in water to form H+ ions

○ Conducts electricity

○ Numbers less than 7 in the pH scale are acids

○ The presence of H+ ions is what makes a solution acidic

● Examples of common acids

○ Hydrochloric acid (HCl)

○ Sulfuric acid (H2SO4)

○ Nitric acid (HNO3)

○ Ethanoic acid (CH3COOH)

● Reactions of Acids

○ Acid + Base → Salt + Water

○ Acid + Metal → Salt + Hydrogen

○ Acid + Carbonate → Salt + Carbon Dioxide + Water

● Alkali

○ A substance which turns red litmus paper blue

○ Have a bitter taste and are slippery

○ Numbers more than 7 in the pH scale are alkalis

○ Disassociates in water to form OH- ions

● Bases

○ A base which is water-soluble is referred to as an alkali

○ Bases are usually oxides and hydroxides of metals

○ Bases are substances which can neutralise an acid, forming a salt and water

● Examples of common alkali

○ Sodium hydroxide/lye (NaOH)

○ Potassium hydroxide (KOH)

○ Calcium hydroxide {Ca(OH)}

○ Ammonia (NH3)

● Chemical indicators

○ Phenolphthalein

■ Colourless(acid)

■ Pink(alkali)

○ Litmus

■ Red(acid)

■ Blue(alkali)

○ Methyl orange

■ red(acid)

■ yellow(alkali)

● Ionic equations

○ State symbols (important)

○ Cancel spectator ions after balancing

○ In neutralization reaction water is only product

● Oxides

○ Elements combining with O2

○ Types of oxides

■ Acidic(non-metal oxides)

■ Basic(metal oxides)

■ Neutral

■ Amphoteric(both acid and base)

● Acidic oxides

○ C + 02 → CO2 +H2O → H2CO3

○ S + O2 → SO2 +H20 → H2SO3

○ 4P + 5O2 → 2P2O5 +H20 → H3PO4

○ N + O2 → NO2 +H2O → HNO3

● Metal/Basic oxides

○ 4Na + 02 → 2Na2O

○ 2Mg + O2 → 2Mgo

○ 4Fe + 3O2 → 2Fe2O3

○ 2Cu + O2 → 2CuO

○ CuO + HCl → CuCl2 + H2O

● Amphoteric oxides

○ Behave like both acid and base

○ ZnO/Al2O3/PaO

● Neutral oxides

○ Neither acid or base

○ CO, N2O, H2O

Soluble salts

Insoluble salts

All sodium

All potassium

All ammonium

All nitrates

All chlorides → except →

Lead(ll), Silver

All sulfates → except →

Barium, Calcium, Lead

Potassium,Sodium,Ammonium ← except ←

All Carbonates

Potassium, Sodium, Ammonium ← except ←

All hydroxides and oxides

● Precipitation

○ Stir the 2 reactants with H20

○ Heat to form precipitate

○ Wash precipitate to remove impurities

○ Dab dry

● Reaction with acids

○ Fill the beaker with H2SO4 then add excess Zn powder until it dissolves. No more H2

bubbles

○ Filter to remove unreacted Zinc powder

○ Take filtrate and heat to concentrate salt

○ Heat till crystallization point, test vy dipping a cold glass rod in filtrate. Stop heating when

crystals form on the rod(solution is saturated)

○ Cool solution for crystallization and filter to collect crystals

○ Wash and dry with filter paper and distilled water

● Solubility for reaction(acid+metal)

○ K, Na, Ca → very reactive, too dangerous to react with acids

○ Mg, Al, Zn, Fe, Pb → Suitable and moderately reactive

○ Cu, Ag → too unreactive

● Titration

○ Apparatus: pipette, burette, conical flask

○ Pipette the base into the conical flask

○ Add indicator(phenolphthalein) to see exactly how much acid and base is present

○ Run acid from burette into conical flask drop by drop

○ Till end/neutralisation point(observe indicator)

○ Repeat without indicator with precise amounts for purity of product

○ Heat, saturate, crystallize, cool, wash, dry