More In-Class Practice Reviewing Bronsted Acid- Base Concepts Let’s do acid !

What observation required Bronsted to create a new Acid/Base Theory different than Arrhenius’s model ? A.Many salts formed conjugate acids. B.Spontaneous acid+base reactions only occurred if weaker acids and bases formed. C.H 2 O spontaneously decomposed to OH- and H+ in presence of various salts. D.Many salts without OH - somehow created OH - in water.

Which part of the Bronsted salt K 3 PO 4 is the proton acceptor ? A.K + B.O 2- C.P 3- D.PO 4 3- E.K 3 PO 4 F.OH -

What new concept of Bronsted’s most directly explains why many salts are bases? A.The anionic part of salts can hydrolyze water. B.Spontaneous acid/base reactions lead to weaker conjugate acids/bases. C.Bronsted bases are proton acceptors. D.Bronsted acids are proton donors.

In-class reaction Jeopardy Low heat, precipitates, cation swap metathesis WHAT IS… Na 2 CO 3 for example A Bronsted base What’s my reaction type: HCl + KOH  KCl + H 2 O Acid/base neutralization (Arrhenius) Pick the Arrhenius acids H 2 O HNO 3 NaHCO 3 HBr NaCl HNO 3 HBr

In-class reaction Jeopardy WHAT IS… What’s my reaction type: K 3 PO 4 + H 2 O  HK 2 PO 4 + KOH Acid/base hydrolysis (Bronsted) Write my products ? AgNO 3 (aq) + NaCl(aq)  ? AgCl(s) + NaNO 3 (aq) Pick the Bronsted base(s) NaOH HBr NaHCO 3 K 3 PO 4 NaOH NaHCO 3 K 3 PO 4 Pick the Arrhenius bases NaOH

OXIDATION-REDUCTION (REDOX) REACTIONS see pages text REDOX REACTIONS ALL INVOLVE CHANGES IN ELECTRON OWNERSHIP EXAMPLE #1 : (w/demo) Mg o + 2H +  Mg 2+ + H Mg loses 2 e - Each H+ gains 1 e- Losing is oxidation Gaining is reduction

Leo-Ger Lose electrons = oxidation Gain electrons =reduction Oxidation-Reduction: Remembering which is which…..

Oil-Rig Oxidation is losing Reduction is gaining Oxidation-Reduction: Remembering which is which…..

Qualitative Features of REDOX Reactions Often involves gross changes in state (solid  gas or solution) Extreme changes in energy (fire, light, explosions) prime engine of living metabolisms (if you breathe, you redox…)

How to know if a reaction is a `redox’ reaction: assign OXIDATION NUMBERS RULES: (SEE PAGE 171 TABLE 4.2) 1) PURE UNCHARGED ELEMENTS HAVE 0 OXIDATION # H 2 O 2 N 2 Fe Cu Au To emphasize, metals often written M o Example: Fe  Fe o

How to know if a reaction is a `redox’ reaction: assign OXIDATION NUMBERS RULES: (SEE PAGE 171 TABLE 4.2) 2) OXIDATION # OF A CHARGED ATOM IS THE CHARGE ITSELF F - Co 3+ H + S

How to know if a reaction is a `redox’ reaction: assign OXIDATION NUMBERS RULES: (SEE PAGE 171 TABLE 4.2) 3) F (AND USUALLY THE OTHER HALOGENS) ARE -1 in binary and larger compounds NaFHClNCl 3 SiOF * -1 * * Each atom of Cl or F is -1

How to know if a reaction is a `redox’ reaction: assign OXIDATION NUMBERS RULES: (SEE PAGE 171 TABLE 4.2) 4) O IS -2 EXCEPT IN PEROXIDES (X-OO-Y) WHERE IT IS -1 H 2 ONaOHK 2 CrO 4 NaMnO * -2* * Each atom of O in compound is -2 HOOH =H 2 O PEROXIDE STRUCTURE

How to know if a reaction is a `redox’ reaction: assign OXIDATION NUMBERS RULES: (SEE PAGE 171 TABLE 4.2) 5)H IS +1 FOR COVALENT COMPOUNDS (AND MOST IONIC ONES TOO) HClNH 3 H 2 O CH * +1* +1* *Each H in the compound is +1

PRACTICE ASSIGNING OXIDATION # N2N2 O2O2 H2OH2O Fe 2 O 3 H 2 SO 4 N=0 O=0 H=+1 O= -2 Fe=+3O= -2 H= +1 O= -2 S=+6 Provide oxidation # for all elements below

Mg(s) + 2HCl(aq)  MgCl 2 (aq) + H 2 (g) 2Al(s) + 3CuSO 4 (aq)  Al 2 (SO 4 ) 3 (aq) + 3 Cu(s) Which element oxidized ? Which element reduced ? Which element oxidized ? Which element reduced ? PRACTICE ASSIGNING OXIDATION #(cont.) Mg H Al Cu w/demo

What are the oxidation # for H, Mn and O in HMnO 4 A.H=+1, Mn=+3, O=-1 B.H=+1, Mn =+7, O=-2 C.H=0, Mn=8, O =-2 D.H=-1, Mn = 9, O=-2

What is oxidized and reduced in the reaction: PbO + CO  Pb+CO 2 A.O reduced, Pb oxidized B.C reduced, Pb oxidized C.Pb reduced, O oxidized D.Pb reduced, C oxidized

What is oxidized and reduced in the reaction: CH 4 +O 2  CO 2 +H 2 O A.C oxidized, O reduced B.H oxidized, C reduced C.C oxidized, H reduced D.O oxidized. C reduced

SPECTACULAR REDOX REACTION BEHAVIOR 2Al o (s) + Fe 2 O 3 (s)  2Fe 0 (liq)+Al 2 O 3 (s) 3)let’s see the reaction in the `flesh’ Which element oxidized ? Which element reduced ? Al Fe 1)assign oxidation # 2) Who does what? 1) Thermite reaction wGQ

SPECTACULAR REDOX REACTION BEHAVIOR (continued) Example 2: Combustion CH 4 +2O 2  CO 2 +2H 2 O 1) Assign Oxidation # Which element oxidized ? Which element reduced ? 2) Who does what? C O BURN BABY, BURN

: 2Na + Cl 2  NaCl (table salt) SPECTACULAR REDOX REACTION BEHAVIOR (continued) Example 3: Combination redox 1) Assign Oxidation # Which element oxidized ? Which element reduced ? 2) Who does what? 3) Let’s see it

C 12 H 22 O K Cl O 3  11H 2 O + 12CO 2 + 8KCl 4) EXAMPLE 4 Decomposition redox: aka The DEATH TO SKITTLES REACTION SPECTACULAR REDOX REACTION BEHAVIOR (continued) Ox Red And now, the dangerous, scary In-class demo…

One other unique and highly useful feature of redox reactions … The oxidation and reduction can be separated in space and you can still run the reaction as a `cell’ or ‘battery’

Example: Cu-Mg cell Cu 2+ + Mg o  Cu o +Mg 2+ The complete redox reaction Reduction half reaction: Cu 2+ +2e -  Cu o cathode Oxidation half reaction: Mg o  Mg 2+ +2e- Gains 2e - Loses 2e- anode Cu 2+ + Mg o  Cu o +Mg 2+

The experimental set-up of (Mg|Mg 2+ ||Cu 2+ |Cu) cell anode cathode LOAD Electron flow out of anode OxidationReduction Mg 0  Mg 2+ +2e - Cu 2+ +2e -  Cu o NaCl bridge Na +   Cl -

Traditional demo Potato clock