Day 71 Notes (Ch. 17 & 20) Electrolytes, Acids and Bases

Electrolytes: Solutions that conduct electrical current easily. Aqueous solutions of acids and bases are electrolytes. Ionic solids that dissolve in water are electrolytes.

NaCl(s)  Na+(aq) + Cl-(aq) Dissociation: Water surrounds ions and dissolves them. Dissociation equation: NaCl(s)  Na+(aq) + Cl-(aq)

Weak Electrolyte: Partial Ionization. Strong Electrolyte: 100% or nearly 100% dissociated. Ionic compounds that dissolve in water conduct electricity easily because ions can move in solution. Weak Electrolyte: Partial Ionization. Ionic compounds that partially dissolve in water do not conduct electricity very well because only about 5% or less of the ions dissociate. Are poor conductors of electricity

Nonelectrolyte: Does not dissolve in water. Covalent or nonpolar substances are nonelectrolytes because they do not dissociate to form ions when dissolved in a solution. Nonelectrolytes do not conduct electricity (Example: Sugar water)

Electrolytes: The ability of a solution to conduct an electric current. The ammeter measures the flow of electrons (current) through the circuit. If the ammeter measures a current, and the bulb glows, then the solution conducts. (Electrolyte) If the ammeter fails to measure a current, and the bulb does not glow, the solution is non-conducting. (Nonelectrolyte)

General definition: Acids: Produce hydrogen ions, H+ , when dissolved in water. Bases: Produce hydroxide ions, OH-, when dissolved in water.

Dissociation of an Acid Cl Cl H H C l H Dissociation equation. HCl  H+ + Cl- General Dissociation equation. HA  H+ + A- A- represents the anion

Acid-Base Neutralization + Base  Water + Salt HCl + NaOH  HOH H2O + NaCl

Some Properties of Acids Acids taste sour Acids react with certain metals to produce hydrogen gas. 2 HCl(aq) + Mg(s)  H2(g) + MgCl2(aq) Acids change the color of indicators Blue litmus turns red Phenolphthalein turns colorless Methyl orange turns red

Acids Effect on Indicators Blue litmus paper turns red in contact with an acid.

Bases Effect on Indicators Red litmus paper turns blue in contact with a base. Phenolphthalein turns purple in a base.

Neutral solutions Red litmus stays red. Blue litmus stays blue.

pH Indicators and their ranges

Hydro_______ic acid Naming Acids Acids without oxygen: HF = Hydrofluoric acid HCl = Hydrochloric acid HBr = Hydrobromic acid HI = Hydroiodic acid H2S = Hydrosulfuric acid HCN = Hydrocyanic acid CN- = cyanide anion

Naming Acids H+ + (anions with oxygen) Acids with oxygen: “ate-ic ite-ous” Anion name Acid name ____ate ____ic acid ___ite ___ous acid HNO3 = Nitr__?__ acid Anion NO3-1 = nitrate Nitric acid HNO2 = Nitr__?__ acid Anion NO2-1 = nitrite Nitrous acid

Naming Acids H+ + (anions with oxygen) Formula H+ with Anion Acid name H2SO4 2H+ + SO42- = sulfate Sulfuric acid H2SO3 2H+ + SO32- = sulfite Sulfurous acid HC2H3O2 H+ + C2H3O2-1 = Acetate Acetic acid H2CO3 2H+ + CO32- = Carbonate Carbonic acid H3PO4 3H+ + PO43- = Phosphate Phosphoric acid

Naming Acids H+ + (series of Cl and O) Formula H+ with Anion Acid name HCl H+ + Cl- = Chloride Hydrochloric acid HClO H+ + ClO-1 = hypochlorite Hypochlorous acid HClO2 H+ + ClO2-1 = Chlorite Chlorous acid HClO3 H+ + ClO3-1 = Chlorate Chloric acid HClO4 H+ + ClO4-1 = perchlorate Perchloric acid Hypo = less oxygen Per = more oxygen

Naming Bases Same method as naming ionic compounds Formula Cation with OH- Base name NaOH Na+ + OH- Sodium hydroxide (Lye) KOH K+ + OH- Potassium hydroxide Ca(OH)2 Ca2+ + 2 OH- Calcium hydroxide (Lime) Mg(OH)2 Mg2+ + 2 OH- Magnesium hydroxide (Milk of magnesia) Al(OH)3 Al3+ + 3 OH- Aluminum hydroxide NH3 (No ions) Ammonia (common name) Molecules that contain nitrogen are weak bases.

Acids Have a pH less than 7

Bases have a pH greater than 7