Example: 2 Na + Cl 2 NaCl

E3 Redox: Transferring electrons

Session one of two ? First hour: Discussion

(E1) ? 2nd and 3rd hour: Lab

(E3, Parts 1 and 2A)

Oxidation-Reduction (Redox)

Reactions involve electron transfer. Change in charge (oxidation state) of reactants.

Example: 2 Na(s) + Cl2 (g) 2 NaCl(s)

Gain of e's = reduction Lose of e's = oxidation (Cl Cl- in NaCl) (Na Na+ in NaCl)

Loss of electrons (LEO) = oxidation Gain of electrons (GER) = reduction

Redox reaction

2 Na + Cl2

LEO

GER

DEMO

2 aCl + energy

1

REDOX Half Reactions

Oxidation ( > in oxidation state) 2 (Na Na+ + e- )

Reduction ( < in oxidation state)

(Cl2 + 2e- 2Cl- )

Half reactions always written to show electron GAIN. The final equation reflects the sum of the balanced half reactions so that electrons lost = electrons gained:

2 Na + Cl2 2 Na + + 2 Cl-

OXIDIZING AGENT REDUCING AGENT

Gains electrons and is reduced (GER)

Loses electrons and is oxidized (LEO)

An oxidizing agent brings about the oxidation of another substance. A reducing agent bring about the reduction of another substance.

Redox Agents

Q. Identify the reducing agents (RA) and oxidizing agents (OA) in the reaction:

2 Na + Cl2 2 a+ + 2 Cl- + energy

_R__A___________O__A___________O__A________R_A___

Oxidation State versus Family Number

Metals lose electrons

Non-metals gain electrons

1A

VIIIA

1 H

1s1 IIA

2 He

IIIA IVA VA VIA VIIA 1s2

34 Li Be

2s1 2s2

5

6

7

8

9

10

B C N O F Ne

2 s22 p12 s22 p2 2 s22 p32 s22 p4 2 s22 p52 s22 p6

11 12 Na Mg

13 14 15 16 17 18 Al Si P S Cl Ar

3s1 3s2 IIIB IVB VB VIB VIIBVIIIB ! VIIIB IB IIB 3s23p13s23p2 3s23p33s23p4 3s23p53s23p6

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 4s1 4s2 3d14 s23d24 s23d34 s23d54 s13d54 s23d64 s2 3d74 s2 3d84 s2 3d1 04s1 3d1 04s2 4 s24 p14 s24 p2 4 s24 p34 s24 p4 4 s24 p54 s24 p6

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 5s1 5s2 4d15 s24d25 s24d35 s24d55 s14d55 s24d75 s1 4d85 s1 4d1 0 4d1 05s1 4d1 05s2 5 s25 p15 s25 p2 5 s25 p35 s25 p4 5 s25 p55 s25 p6

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba La* Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 6s1 6s2 5d16 s25d26 s25d36 s25d46 s25d56 s25d66 s2 5d76 s2 5d96 s1 5d1 06s1 5d1 06s2 6 s26 p16 s26 p2 6 s26 p36 s26 p4 6 s26 p56 s26 p6

8 7 8 8 8 9 1 0 4 1 0 5 1 0 6 1 0 7 1 0 8 1 0 9 + Element synthesized,

Fr Ra Ac# + + +

++

+ but no official name assigned

7s1 7s2 6d17 s26d27 s26d37 s26d47 s26d57 s26d67 s2 6d77 s2

2

Nonmetals gain electrons and reduce (GER)

1 1A

2 IIA

18 VIIIA

- 5 - 4 - 3 - 2 -1 2 13 14 15 16 17 He IIIA IVA VA VIAVIIA 1s2

5 6 7 8 9 10 B C N O F Ne 2 s22 p12 s22 p22 s22 p3 2 s22 p42 s22 p5 2 s22 p6

3 4 5 6 7 8 9 10 11 12 IIIB IVB VB VIB VIIB VIIIB ! VIIIB IB IIB

14 15 16 17 18 Si P S Cl Ar

3 s23 p23 s23 p3 3 s23 p43 s23 p5 3 s23 p6

33 34 35 36 As Se Br Kr

4 s24 p3 4 s24 p4 4 s24 p54 s24 p6

52 53 54 Te I Xe

5 s25 p45 s25 p5 5 s25 p6

+ Element synthesized,

but no official name assigned

85 86 At Rn

6 s26 p5 6 s26 p6

+1

1

18

1A

Family A Metals

+3 +4 +5 +6

VIIIA

1 +2 H 2

Q1. Maximum charge vs. family# ? +1 +2 +3 +4

13 14 15 16

17

1s1 IIA Q2. Possible oxidation states of Sn? IIIAIVA VA VIA VIIA

3 4 Li Be 2s1 2s2

11 12

13

Na Mg 3 4 5 6 7 8 9 10 11 12 Al 3s1 3s2 IIIB IVB VB VIB VIIB V I I I B ! VIIIB IB IIB 3s23p1

19 20 21 22 23 24 25 26 27 28 29 30 31 32 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge 4s1 4s2 4s23d1 4s23d2 4s23d3 4s13d5 4s23d5 4s23d6 4s23d7 4s23d8 4s13d10 4s23d10 4s24p1 4s24p2

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb 5s1 5s2 5s24d125s24d2 5s24d3 5s14d5 5s23d5 5s14d7 5s14d8 4d10 5s14d10 5s24d10 5s25p1 5s25p2 5s25p3

5 5 5 6 5 7 7 2 7 3 74 7 5 7 6 7 7 7 8 7 9 8 0 8 1 8 2 83 8 4

Cs Ba L a * Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po

6s1 6s2 6s25d1 6s25d2 6s25d3 6s25d4 6s24d5 6s25d6 5d76s2 6s15d9 6s15d10 6s25d10 6s26p1 6s26p2 6s26p3 6s26p4

8 7 8 8 8 9 1 0 4 1 0 5 1 0 6 1 0 7 1 0 8 109 + Element synthesized,

Fr Ra Ac# + + +

+ + + but no official name assigned

7s1 7s2 7s26d1 7s26d2 7s27d3 7s26d4 7s23d5 6s26d6 6d77s2

Ions with multiple oxidation states

Q. Sn (Group IVA) has oxidation states of zero, plus two, and plus four. Write half reactions depicting:

Reduction of Sn2+ ion: Sn2+ + 2 e- Sn

Oxidation of Sn2+ ion: Sn2+ Sn4+ + 2 e-

Sn2+ can act as an oxidizing or reducing agent in redox reactions!

1

Transition Metals

18

1A Q. Maximum oxidation state vs. family # ?

VIIIA

1

H2

13 14 15 16 17

1s1 IIA

IIIA IVA VA VIA VIIA

34 Li Be

2s1

2s2

+2 !

+2 +2 +2 +2 ! !! !

11 12 +3 +4 +5 +6 +7

+2

+1 +2 1 3

Na Mg 3 4 5 6 7 8 9 10 11 12 Al

3s1 3s2 IIIB IVB VB VIB VIIB VIIIB " VIIIB IB IIB 3s23p1

19 20 21 22 23 24 25 26 27 28 29 30 31 32 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge 4s1 4s2 4s23d14s23d24s23d34s13d54s23d54s23d6 4s23d7 4s23d8 4s13d10 4s23d10 4s24 p14s24 p2

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb 5s1 5s2 5s24d152s24d25s24d3 5s14d55s23d55s14d7 5s14d8 4d1 0 5s14d10 5s24d10 5s25 p15s25 p25s25 p3

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84

Cs Ba La* Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po 6s1 6s2 6s25d16s25d26s25d3 6s25d46s24d56s25d6 5d76s2 6s15d96s15d10 6s25d10 6s26 p16s26 p26s26 p3 6s26 p4

8 7 8 8 8 9 1 0 4 1 0 5 1 0 6 1 0 7 1 0 8 1 0 9 + Element synthesized,

Fr Ra Ac# + + +

+ + + but no official name assigned

7s1 7s2 7s26d17s26d27s27d3 7s26d47s23d56s26d6 6d77s2

3

Strength of Redox Agents

Example: 2 Na + Cl2 2 a+ + 2 Cl-

__R_A____________O__A___________O_A________R__A__

The reactants are the stronger RA and OA and react spontaneously The non-reactive products are the weaker OA and RA.

RA: Na > Cl- OA: Cl2 > Na+

Redox agent strength

Q. Rank the strength of the reducing/oxidizing agents in the reaction below:

2 Sb + 3 Cl2 2 Sb3+ + 6 Cl-

RA

OA

OA

RA

RA strength:_S_b_ >_C_l_- OA strength: _C_l_2 >_S_b_ 3+

Reaction and Redox Strength If RA: Cu > Ag OA: Ag+ > Cu2+

Reactants

Cu(s) + Ag+(aq) ?

Ag(s) + Cu2+(aq) ?

DEMO

Reactions and Redox Strength The stronger RA and OA react:

Cu(s) + Ag+(aq)

reaction

The weaker RA and OA do NOT react:

Ag(s) + Cu2+(aq) no reaction

4

Part I B. Predicting Metal Reactivity.

? Determine the reducing agent (RA) strength of four team assigned metals where the metal ions of all four metals are available and only three of the four metals are available for experimental tests.

Experiment Design and Data Analysis

Example You need to determine the reducing agent strength of Zn, Cu, and Mg.

Problem Available: Solutions of Zn2+, Cu2+, and Mg2+.

Zn and Cu only (i.e., Mg is unavailable)

Experiment Design for Part 1B.

Create a table for recording data (pre-lab).

?Zn2+ ?Cu2+ ?Mg2+ ?Zn ?Cu ?Mg Reducing agent species (metals) on one side and oxidizing agents species (metal ions) on other side.

Experiment Design and Data Analysis

Test available metal and metal ion combinations Record observations

Example:

Zn(s) + Cu2+ (aq) reaction

5

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download