Chemistry 141 Lecture 6 Monday, September 18, 2017

Objectives for today Predict and write chemical formulas Name chemical compounds Write and balance chemical equations Identify types of reactions (combination, decomposition, and combustion)

Ionic Compounds

Your turn For each of the following pairs, predict the ionic compound they form Mg and Cl Fe(III) and O K and N

Chemical Nomenclature Common names (water, ammonia, etc.) Ionic compounds Cations Group 1 and 2 metals (first 2 columns): same name as element Transition metals Add Roman numeral to denote charge: e.g. Fe3+  Iron (III) Or, use Latin names: e.g. Fe3+  ferric ion, Fe2+  ferrous ion Molecular cations tend to end in “ium”: e.g. NH4+  ammonium, H3O+  hydronium

Chemical Nomenclature Common names Ionic compounds Cations Anions Monatomic anions: replace suffix with “ide” Cl-  chloride N3-  nitride Polyatomic anions containing oxygen (oxyanions) Most “common”  ends in “ate” One less oxygen than “ate” version  ends in “ite”

Chemical Nomenclature Common names Ionic compounds Cations Anions Monatomic anions: replace suffix with “ide” Polyatomic anions containing oxygen (oxyanions) Most “common”  ends in “ate” One fewer oxygen than “ate” version  ends in “ite” One more oxygen than “ate” version  starts with “per” / ends in “ate” One fewer oxygen than “ite” version  starts with “hypo” / end in “ite” ClO- = hypochlorite ClO2- = chlorite ClO3- = chlorate ClO4- = perchlorate

Chemical Nomenclature Common names Ionic compounds Cations Anions Monatomic anions: replace suffix with “ide” Polyatomic anions containing oxygen (oxyanions) Oxyanions containing hydrogen One hydrogen: add “hydrogen” to start of name (add +1 to charge) Two hydrogens: add “dihydrogen” to start of name (add +2 to charge) PO43- = phosphate HPO42- = hydrogen phosphate H2PO4- = dihydrogen phosphate

Chemical Nomenclature Common names Ionic compounds Cations Anions Compounds LiF  ? aluminum sulfite  ? FeHPO4  ?

Chemical Nomenclature Common names Ionic compounds Cations Anions Compounds Hydrates (some ionic compounds include “waters of hydration”) Use latin number prefix and add –hydrade (e.g. trihydrade) FeCl3  iron (III) chloride FeCl3 • 6H2O  iron (III) chloride hexahydrate

Chemical Nomenclature Common names Ionic compounds Acids (anions with hydrogen cations (H+)) From anions ending in “ide”  prefix “hydro”, change “ide” to “ic acid” From oxyanions For oxyanions ending in “ate”  change “ate” to “ic acid” For oxyanions ending in “ite”  change “ite” to “ous acid” HI  hydroiodic acid HNO3  nitric acid (H2SO4  sulfuric acid) HClO  hypochlorous acid

Chemical Nomenclature Common names Ionic compounds Acids Binary molecular compounds The leftmost (or bottom-most) element on the periodic table goes first … unless it’s oxygen, which always goes last … unless oxygen is paired with fluorine, and then it’s first again The name of the second element is given the “ide” suffix Use Greek prefixes (mono, di, tri, tetra, etc.) to indicate number of atoms … but don’t use “mono” for first element PCl5  phosphorous pentachloride N2O3  dinitrogen trioxide

Chemical Nomenclature Common names Ionic compounds Acids Binary molecular compounds Basic organic compounds Alkanes (contain only C and H): CH4 = methane Alcohols (contain an OH group): CH3OH = methanol Organic acids (contain a COOH group): CH3COOH = acetic acid

Your turn For each pair below: Predict the formula of the compound they form Write the name of the compound Ca and NO3- Cr(III) and SO42- NH4+ and S H and PO43- 2 N’s and 5 O’s

The Law of Conservation of Mass Matter cannot be created or destroyed (Lavoisier, “The father of modern chemistry”, 1789) “…an equal amount of matter exists both before and after the experiment. Upon this principle, the whole art of performing chemical experiments depends.”

CH4(g) + 2O2(g) CO2(g) + 2H2O(g) States of matter CH4(g) + 2O2(g) CO2(g) + 2H2O(g) The states of the reactants and products are written in parentheses to the right of each compound. (g) = gas (l) = liquid (s) = solid; (aq) = in aqueous solution

Your turn How many atoms of Mg, O, and H are represented by the notation 3 Mg(OH)2? 1 Mg, 2 O, and 2 H 2 Mg, 2 O, and 2 H 6 Mg, 6 O, and 6 H 3 Mg, 6 O, and 6 H Answer: d

Balance the following equations: TiCl4 (l) + H2O (l)  TiO2 (s) + HCl (aq) AlCl3 (s) + Ca3N2 (s)  AlN (s) + CaCl2 (s) C6H6 + O2  CO2 + H2O

Three Types of Reactions Combination reactions Decomposition reactions Combustion reactions

Combination Reactions In combination reactions two or more substances react to form one product. 2 Mg(s) + O2(g) 2 MgO(s)

Decomposition Reactions In a decomposition reaction one substance breaks down into two or more substances. 2 NaN3(s) 2 Na(s) + 3 N2(g)

Combustion Reactions CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g) Combustion reactions most often involve oxygen in air as a reactant and can produce a flame. CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g)