Electrolytes, Weak and Strong Electrolytes are compounds that ionize in water to produce aqueous solutions that conduct an electric current. Nonelectrolytes are substances that do not ionize, remain as molecules, and do not conduct an electric current. Strong electrolytes are molecules that ionize 100% (or nearly so) and conduct an electric current well. Weak electrolytes barely or partially ionize; most molecules remaining un-ionized, and conduct an electric current poorly.

Examples Nitric acid (HNO3) is a strong electrolyte. HNO3  H+1 + NO3-1 If 1.00 mole of HNO3 is dissolved in water, it will ionize to produce 1.00 mole of H+1 and 1.00 mole of NO3-1 . There will not be any HNO3 left, unionized. By contrast, one mole of a weak electrolyte will produce much less than 1.00 mole of its constituent ions. One mole of acetic acid HC2H3O2 ↔ H+1 + C2H3O2-1 might produce 0.05 moles of H+1 and 0.05 moles of C2H3O2-1 and still contain 0.95 moles of the original acetic acid.

Another Example: Calculate the concentrations of ions in a 0.015 M Ba(OH)2 solution. Ba(OH)2 is a strong electrolyte. Hint: What is the valency of Ba? What ion will it form? Where will the extra electrons go?

Solubility Rules Soluble Compounds 􀂄 Sodium, potassium, and ammonium compounds 􀂄 Acetates and nitrates 􀂄 Halides (chlorides, bromides, and iodides) 􀂄 Sulfates Exceptions Lead(II), silver, and mercury(I) halides are insoluble Calcium, strontium, barium, and lead(II) sulfates are insoluble

Solubility Rules Insoluble Compounds 􀂄 Carbonates and phosphates 􀂄 Hydroxides 􀂄 Sulfides Exceptions Sodium, potassium, and ammonium carbonates and phosphates are soluble Alkali hydroxides and barium hydroxide is soluble whereas strontium and calcium hydroxide are slightly soluble Sodium, potassium, calcium, and ammonium sulfides are soluble

Precipitation is the Opposite to Dissolution Whenever the concentration of a substance in solution exceeds its solubility, precipitation occurs. Can cause precipitation of a solution by remove solvent add solute change solvent change temperature

Acids and Bases Arrhenius Acids and Bases H2O(l) H+(aq) + OH-(aq) Three main definitions for acids and bases: After Arrhenius After Lewis After Bronsted-Lowry Arrhenius Acids and Bases H2O(l) H+(aq) + OH-(aq) Autoionization or self-dissociation of water is an intrinsic property and cannot be suppressed

Arrhenius Acids and Bases An Arrhenius Acid is a substance that, when dissolved in water, delivers hydrogen ions H+(aq) to the solution, i.e., it increases the concentration of hydrogen ions. e.g., HCl(g) H+(aq) + Cl- (aq) An Arrhenius Base is a substance that, when dissolved in water, delivers hydroxide ions OH-(aq) to the solution, i.e., it increases the concentration of hydroxide ions. e.g., NaOH(s) Na+(aq) + OH-(aq)

Hence…… [OH-(aq)] = [H+(aq)] H2O(l) H+(aq) + OH-(aq) Water is both, an Arrhenius Acid and an Arrhenius Base! Such a substance that acts as both acid and base is called amphoteric. In pure water, the concentration of hydroxide ion equals the concentration of hydrogen ion so that [OH-(aq)] = [H+(aq)]

The Neutralization Reaction … is the reaction between an acid -- excess H+(aq) -- and a base -- excess OH-(aq) -- leading to the formation of neutral H2O and a salt that can either precipitate or stay in solution depending on its solubility. e.g., HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) H2O(l) + Cl-(aq) + Na+(aq) Net: H+(aq) + OH-(aq) H2O(l)

Acids HCl(g) H+(aq) + Cl-(aq) HNO3(g) H+(aq) + NO3-(aq) Monoprotic Acids HCl(g) H+(aq) + Cl-(aq) HNO3(g) H+(aq) + NO3-(aq) Diprotic Acids H2SO4(aq) H+(aq) + HSO4-(aq) HSO4-(aq) H+(aq) + SO42-(aq) Triprotic Acids H3PO4(l) H+(aq) + H2PO4-(aq) H2PO4-(aq) H+(aq) + HPO42-(aq) HPO42-(aq) H+(aq) + PO43-(aq)

The Name Game A binary acid is formed by hydrogen with a second element. For binary acids use the prefix hydro-, attach it to the name of the element, and end with –ic. Examples: HF – hydrofluoric acid HCl –hydrochloric acid Of course, these also have names as covalent compounds … …

The Name Game An oxoacid is formed by hydrogen with an oxoanion. For oxoacids, if the oxoanion ends in -ate, replace –ate with –ic and add the word acid. If the oxoanion ends in –ite, replace –ite with –ous, and add the word acid. The prefix per- (meaning largest number of oxygen atoms in the oxoacid) and hypo- (meaning smallest number of oxygen atoms in the oxoacid) is used when more than one possibility exists.

The Name Game Examples: ClO- hypochorite anion HClO hypochlorous acid ClO2- chlorite anion HClO2 chlorous acid ClO3- chlorate anion HClO3 chloric acid ClO4- perchlorate anion HClO4 perchloric acid SO32- sulfite anion H2SO3 sulfurous acid SO42- sulfate anion H2SO4 sulfuric acid

The Name Game O O + H+ R R C C O-H O An organic acid has one or more –COOH groups. The naming is not systematic but involves the –ate anion becoming the –ic acid. Examples follow: HCOO - formate anion HCOOH formic acid CH3COO- acetate anion CH3COOH acetic acid CH3CHOHCOO- lactate anion CH3CHOHCOOH lactic acid O O H+ + R R C C O-H O

Produce H+ in aqueous solution to limited extent Strong acids Weak acids Dissociate virtually completely Produce H+ in aqueous solution to limited extent HCl HNO3 H2SO4 HClO4 HF CH3COOH (acetic acid) HCOOH (formic acid) Discuss H2SO4 in more detail.

Typical Bases Weak bases Strong bases Dissolve only slightly in water Easily soluble in water Dissolve only slightly in water but can neutralize acids Mg(OH)2, NH3 NaOH KOH Ba(OH)2 Mg(OH)2+ HCl(aq) H2O(l) + MgCl2(aq)