Chemistry, The Central Science, 10th edition Theodore L. Brown;. Eugene LeMay, Jr.; and Bruce E. Bursten Unit 4 (Chapter 4): Aqueous Reactions & Solution Stoichiometry John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice all, Inc.
Solutions: + homogeneous mixtures: evenly mixed (same) solvent is present in greatest abundance. solute dissolved in/by solvent
Molarity Molarity (M) is a measure of the concentration of a solution. Molarity (M) = moles of solute (mol) liters of solution (L) units: mol/l or mol L 1 What s the concentration of a solution with 29.2 g of sodium chloride in 250. ml of water? 29.2 g NaCl x 1 mol NaCl 58.44 g NaCl = 0.500 mol NaCl = 2.00 M 0.250 L NaCl
Solution Prep from Solid 1-Calc & Mass solute 2-Add solvent, swirl to dissolve 3-Fill with DI water to mark 4-Mix (Cap & Invert to mix evenly) WS #1-2 Conc. Calc s
WS Concentration & Dilutions #1 5.00 g NaCO 3 x 1 mol NaCO 3 84.01 g NaCO 3 x 1 L NaCO 3 = 0.100 mol NaCO 3 0.595 L NaCO 3 #2 0.275 L CuSO 4 x 1.20 mol CuSO 4 x 159.62 g CuSO 4 = 1 L CuSO 4 1 mol CuSO 4 52.7 g CuSO 4
Solution Prep by Dilution 1-Calc M 1 V 1 =M 2 V 2 2-Pipet V 1 from concentrated 3-Fill to mark with DI water 4-Mix (Cap & Invert to mix evenly) M 1 V 1 = M 2 V 2 WS #3-4 Dilutions
WS Concentration & Dilutions M 1 V 1 = M 2 V 2 W p.160 #60, 67 #3 M 1 V 1 = M 2 V 2 (12.0 M)V 1 = (1.25 M)(500. ml) V 1 = 52.1 ml (or 0.0521 L) #4 M 1 V 1 = M 2 V 2 (2.50 M)V 1 = (0.200 M)(250. ml) V 1 = 20.0 ml (or 0.0200 L)
Cl O O + Cl Cl + 2 O 3 O + + Cl Acid: proton ( + ) donor Base: proton ( + ) acceptor N 3 + 2 O N 4+ + O N O N O +
Strength of Acids and Bases STRONG: (complete ionization) (completely as ions) A(aq) MO(aq) + (aq) + A (aq) M + (aq) + O (aq) WEAK: (partial ionization) (mostly as molecules) A(aq) + 2 O(l) B(aq) + 2 O(l) 3 O + (aq) + A (aq) B + (aq) + O (aq)
Strong Acids: I + 2 O 3 O + + I proton ( + ) donors Only 6 strong acids: Nitric (NO 3 ) Sulfuric ( 2 SO 4 ) ydrochloric (Cl) ydrobromic (Br) ydroiodic (I) Perchloric (ClO 4 )
The strong bases are Strong Bases: soluble hydroxides O + (O ) of 3 O + 2 O + 2 O Group 1 (Li,Na,K) proton ( + ) acceptors CBS (Ca, Ba, Sr) Mg(O) 2 & Be(O) 2 are not soluble ydroxides of Group I ase and CBS
Salts: Ionic Solids: (metal-nonmetal) dissociate (dissolve) by separation into ions Electrolytes: ions in solution that conduct electricity
Non Weak Strong C 11 22 O 11 C 3 O 2 O C 3 COO NO 2 N 3 NaO NO 3 KCl only molecules NO ions partially ionize SOME ions W p.159 #33 ALL ions completely dissociate
Electrolytes: Strong, Weak, or Non? (ions conduct electricity) Compound metal-nonmetal Ionic W p.157 #1,2,4,5,38 nonmetals (Covalent) Molecular Acid ( ) STRONG KBr CaI 2 STRONG FeCl 3 (6) NaO Cl, Br, I Ca(O) 2 NO 3 (strong bases) 2 SO 4 ClO 4 Weak Base WEAK (& N 3 ) C 3 COO NO 2 F Not Acid NON C 11 22 O 11 C 2 5 O 2 O
QUIZ!!! (at the bell) Electrolytes: Strong, Weak, or Non? metal-nonmetal Compound nonmetals (Covalent) Ionic Molecular STRONG STRONG (6) Acid ( ) Weak Base WEAK (& N 3 ) Not Acid NON
Acid-Base Neutralization Reactions strong acid ( + A ) strong base (M + O ) ionic compound (M + A ) water 2 O (O) ACID + BASE SALT + WATER Cl Na O Na + Cl O Cl(aq) + NaO(aq) NaCl(aq) + 2 O(l) W p.159 #40a
Precipitation Reactions Double Replacement: (precipitate) 2 (aq) + (aq) 2 (aq) + ( ) precipitate: insoluble product (as predicted by solubility rules) Pb 2+ I
* * * ALWAYS Soluble ions: Li +, Na +, K +,... + N 4 NO 3 Solubility Rules Group I (alkali metals) ammonium nitrate Common Precipitates form with: examples Ag +, Pb 2+, g 2+ (AP/) AgCl, PbI 2 O (hydroxide) Cu(O) 2 CO 2 3 (carbonate) CaCO 3 WS Solubility & NIE s #1
Molecular Equation reactants and products in molecular form AgNO 3 (aq) + KCl(aq) AgCl(s) + KNO 3 (aq) Ionic Equation Strong Electrolytes are Dissociated as ions (strong acids, strong bases, soluble salts) Ag + (aq) + NO 3 (aq) + K + (aq) + Cl (aq) AgCl (s) + K + (aq) + NO 3 (aq)
Net Ionic Equation (NIE) Cross out Spectator Ions (no change) (same state) (same charge) only species left are those that react (change) during the course of the reaction. Ag + (aq) + NO 3 (aq) + K + (aq) + Cl (aq) Net NIE: AgCl (s) + K + (aq) + NO 3 (aq) Ag + (aq) + Cl (aq) AgCl (s)
Balanced Net Ionic Equations comp diss cross net bal 1. Write a Complete molecular equation. 2. Dissociate all strong electrolytes(aq). 3. Cross out spectators (same charge & state) 4. Write the Net ionic equation with the species that remain. 5. Balance the NIE. (solubility rules)
Balanced Net Ionic Equations comp diss cross net bal + 2 2+ + 1) (N 4 ) 2 SO 4 + Ba(NO 3 ) 2 Ba 2+ + SO 4 2 BaSO 4 BaSO 4 + N 4 NO 3 + 2+ + 2) NaO + MgBr 2 NaBr + Mg(O) 2 Mg 2+ + 2 O Mg(O) 2 (s) W p.158 #21
Neutralization Reactions When a Strong Acid reacts with a Strong Base, the net ionic equation is + + O 2 O Cl(aq) + NaO(aq) NaCl(aq) + 2 O(l) + + Cl + Na + + O Na + + Cl + 2 O
Neutralization Reactions When a Weak acid reacts with a Strong base, the net ionic equation is X + O X + 2 O F(aq) + KO(aq) KF(aq) + 2 O(l) (dissociate ONLY STRONG electrolytes) F + K + + O K + + F + 2 O W p.159 #40 (finish)
Balanced Net Ionic Equations comp diss cross net bal + 2 2+ + (N 4 ) 2 SO 4 + Ba(NO 3 ) 2 BaSO 4 + N 4 NO 3 Ba 2+ + SO 4 2 BaSO 4 (s) + F(aq) + KO(aq) KF(aq) + 2 O(l) + F + O F + 2 O WS Solubility & NIE s #2
Gas-Forming Reactions 2 Demo (M 0 ) ( + ) (M + ) (gas) Single Rep: Metal + Acid Metal Ion + 2 + 2 2+ 2 Ex: Zn(s) + 2 SO 4 (aq) NIE: Zn(s) + 2 + (aq) ZnSO 4 (aq) + 2 (g) Zn 2+ (aq) + 2 (g) (gas) CO 2 Demo ( + ) (CO 2 3 ) 2 O(l) + CO 2 (g) Double Rep: Acid + Carbonate Salt + 2 CO 3 (aq) (or Bicarbonate) (decomposes W p. 159 #43 (CO 3 ) immediately) Ex: Cl(aq) + CaCO 3 (s) NIE: 2 + (aq) + CaCO 3 (s) CaCl 2 (aq) + 2 O(l) + CO 2 (g) Ca 2+ (aq) + 2 O(l) + CO 2 (g) C 3 COO + NaCO 3 C 3 COONa + 2 O + CO 2
g A Solution Stoichiometry Rxn: A(aq) + 2 B(aq) C + 2 D molar mass A g A 1 mol A g B 1 mol B molar mass B mol A mol-to-mol ratio molarity A (M) mol A 1 L mol B 1 L molarity B (M) L of A W p. 161 #81 g B mol B L of B
Oxidation-Reduction Reactions video clip (REDOX) (One cannot occur without the other) LEO says GER
Oxidation Numbers Is it a redox reaction? To find out 1) assign oxidation numbers* (or oxidation states) to each element in a reaction. 2) check if any oxidation states changed ( reduced, oxidized) *charges of ions show electrons transferred IN an ionic compound *oxidation numbers of elements describe electrons that would be lost or gained IF the compound was 100% ionic. in Na 2 O, O 2 in 2 O, O 2
Assigning Oxidation Numbers 1. All pure elements are 0 2. Monatomic ion is its charge (Mg 2+ has +2) 3. Most nonmetals tend to be negative, but some are positive in certain compounds or ions. (in SO 3, O is 2 but S is +6) O is 2 always but in peroxide ion is 1 (O 2 2 ) is +1 with nonmetals, 1 with metals F is always 1. other halogens are 1, BUT can be positive, like in oxyanions. 2 Ex. ClO 3 or NO 3 or SO 4
Oxidation Numbers The sum of the ox. # s in a neutral compound is 0. The sum of the ox. # s in a polyatomic ion is the charge on the ion. Determine the oxidation number of: Sulfur in SO 2 Chromium in K 2 Cr 2 O 7 Nitrogen in N 4 + Cobalt in [CoCl 6 ] 3
Classifying REDOX Reactions All rxns (but NOT double replacement) Synthesis A + B AB 2 1 (0 0 +/ ) Decomposition AB A + B 1 2 (+/ 0 0) Single Replacement AB + C A + CB (+/ 0 0 +/ ) Combustion C x y + O 2 CO 2 + 2 O ( /+ 0 +/ +/ )
Single Replacement (REDOX) silver ions oxidize copper metal Cu(s) + 2 Ag + (aq) X Cu 2+ (aq) + 2 Ag(s) Cu 2+ (aq) + 2 Ag(s) Cu(s) + 2 Ag + (aq)
Activity Series of Metals Cannot displace + from acid to make 2 (g) increasing ease of oxidation
Writing REDOX Reactions Write the net ionic equation for the reaction of solid zinc in a solution of hydrochloric acid. comp diss cross net bal 0 +1 1 +2 1 0 Mg(s) + Cl(aq) MgCl 2 (aq) + 2 (g) Mg + 2 + Mg +2 + 2 Classify the reaction in two ways. Single-Replacement and Redox
ox Mg + 2 + Mg 2+ WS Aq Soln s & Chem Rxns + 2 (g) red What is red & what is ox?