•EXAM #2 MOVED TO FRIDAY, 10/16

Announcements

What is the oxidation number of Cl in NaOCl?

1 2 3 4 5 6 7 8 9

5% 5%

10%

6% 6%

10%

19%

10%

29%

1. +52. +43. +34. +25. +16. 07. -18. -29. -3

Recognizing Redox Reactions

Metals reacting with Nonmetals: 2 Al + 3 Br2 Al2Br6

Almost anything with Oxygen:2 Mg + O2 2 MgO S + O2 SO2

Organic Compounds:CH4 + 2 O2 CO2 + H2O

Others, more difficult to detect:5 Fe2+ + MnO4

- + 8 H+ 5 Fe3+ + Mn2+ + 4 H2O

Examples

4 Al(s) + 3 O2(g) 2 Al2O3(s)

CuO(s) + H2(g) Cu(s) + H2O()

Examples

CaCO3(s) CaO(s) + CO2(g)

MnO4-(aq) + 5 Fe2+(aq) + 8 H+(aq) Mn2+(aq) + 4

H2O() + 5 Fe3+(aq)

Examples

2 H2O2(aq) 2 H2O() + O2(g)

CaCO3(s) + 2 H+(aq) CO2(g) + H2O() + Ca2+(aq)

Cool Redox Demo

Vitamin C is an antioxidant I2 binds to starch black

ascorbic acid + I2 2 I- + dehydroascorbic acid

Types of Reactions

Combination(Synthesis)

Decomposition Displacement

# reactants > # products # reactants < # products # reactants = # products(usually)

SpontaneousHeatElectrolysisCatalyst

Single

Double: Precipitation

Double:Acid-BaseGas forming

Redox

Cool Redox Redux

Elephant Toothpaste

I-(aq)

2H2O2(aq) → 2H2O(g) + O2(g) + Energy