E3 Redox: Transferring electrons. Oxidation-Reduction (Redox)

E3 Redox: Transferring electrons Session one of two • First hour: Discussion (E1) • 2nd and 3rd hour: Lab (E3, Parts 1 and 2A) Oxidation-Reduction (R...
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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) →

Lose of e’s = oxidation (Na → Na+ in NaCl)

2 NaCl(s)

Gain of e’s = reduction (Cl → Cl- in NaCl)

Redox reaction

2 Na LEO

+

Cl2



2 ΝaCl + energy

GER DEMO

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

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REDOX Half Reactions Oxidation ( > in oxidation state)

Reduction ( < in oxidation state)

2 (Na → Na+ + e- )

( Cl2 + 2e- → 2Cl- )

OXIDIZING AGENT

REDUCING AGENT

Gains electrons

Loses electrons and is oxidized (LEO)

and is reduced (GER)

 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-

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

Oxidation State versus Family Number

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

2 Na

+

Cl2

→ 2

Νa+

+ 2

Cl-

RA OA OA RA _________________________________________

+ energy

Metals lose electrons

Non-metals gain electrons

1A

VIIIA

1

2

H

He

1 s1

IIA

IIIA IVA VA VIA VIIA

1 s2

3

4

5

10

2s1 11

2s2 12

3s1

3s2

19

20

4s1 37

4s2 38

10 1 10 2 3d1 4 s2 3d2 4 s2 3d3 4 s2 3d5 4 s1 3d5 4 s2 3d6 4 s2 3d7 4 s2 3d8 4 s2 3d 4 s 3d 4 s 4 s2 4 p14 s2 4 p2 4 s2 4 p3 4 s2 4 p4 4 s2 4 p5 4 s2 4 p6

5s1 55

5s2 56

10 1 10 2 4d1 5 s2 4d2 5 s2 4d3 5 s2 4d5 5 s1 4d5 5 s2 4d7 5 s1 4d8 5 s1 4d1 0 4d 5 s 4d 5 s 5 s2 5 p1 5 s2 5 p2 5 s2 5 p3 5 s2 5 p4 5 s2 5 p5 5 s2 5 p6

6s1 87

6s2 88

7s1

7s2

5d1 6 s2 5d2 6 s2 5d3 6 s2 5d4 6 s2 5d5 6 s2 5d6 6 s2 5d7 6 s2 5d9 6 s1 5d 6 s 5d 6 s 6 s2 6 p1 6 s2 6 p2 6 s2 6 p3 6 s2 6 p4 6 s2 6 p5 6 s2 6 p6 89 1 0 4 1 0 5 1 0 6 1 0 7 1 0 8 1 0 9 + Element synthesized, Ac# + + + + + + but no official name assigned 6d1 7 s2 6d2 7 s2 6d3 7 s2 6d4 7 s2 6d5 7 s2 6d6 7 s2 6d7 7 s2

Li Na

K

Rb Cs Fr

Be

B

Sr

Ba Ra

C

7

N

8

O

9

F

Ne

2 s2 2 p1 2 s2 2 p2 2 s2 2 p3 2 s2 2 p4 2 s2 2 p5 2 s2 2 p6

13

Mg

Ca

6

Al

Sc 39

Y

57

22

Ti 40

Zr 72

La * Hf

23

V

41

Nb 73

Ta

24

Cr 42

25

43

Mo Tc 74

W

26

Mn Fe

75

Re

44

Ru 76

Os

27

Co 45

Rh 77

Ir

28

Ni 46

Pd 78

Pt

29

30

Cu

49

Cd

79 10

Ga

48

Ag Au

31

Zn

47

In

80 1

Hg 10

Si

15

P

16

S

17

Cl

18

Ar

3 s2 3 p1 3 s2 3 p2 3 s2 3 p3 3 s2 3 p4 3 s2 3 p5 3 s2 3 p6

IIIB IVB VB VIB VIIBVIIIB ! VIIIB IB IIB 21

14

81 2

Tl

32

Ge 50

Sn 82

Pb

33

As 51

Sb 83

Bi

34

Se 52

Te 84

Po

35

Br 53

I

85

At

36

Kr 54

Xe 86

Rn

2

+1 1

Nonmetals gain electrons and reduce (GER) 1 1A

18 VIIIA

-5

2 IIA

13

-4

14

-3

15

-2

16

-1

17

IIIA IVA VA VIA VIIA 5

B

6

C

7

N

8

O

9

F

2

He 1 s2

10

Ne

2 s2 2 p1 2 s2 2 p2 2 s2 2 p3 2 s2 2 p4 2 s2 2 p5 2 s2 2 p6

3 4 5 6 7 8 9 10 IIIB IVB VB VIB VIIB VIIIB ! VIIIB

11 IB

12 IIB

14

Si

15

P

16

S

17

Cl

18

Ar

3 s2 3 p2 3 s2 3 p3 3 s2 3 p4 3 s2 3 p5 3 s2 3 p6

33

As

34

Se

35

Br

36

Kr

4 s2 4 p3 4 s2 4 p4 4 s2 4 p5 4 s2 4 p6

52

Te

18

1A

53

I

54

Xe

5 s2 5 p4 5 s2 5 p5 5 s2 5 p6

85

At

86

Rn

6 s2 6 p5 6 s2 6 p6

+

Element synthesized, but no official name assigned

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

Sn2+

Reduction of ion: Sn2+ + 2 e- → Sn Oxidation of Sn2+ ion: Sn2+ → Sn4+ + 2 e-

1

+3 +4 +5 +6 Q1. Maximum charge vs. family# ? +1 +2 +3 +4

+2

H 2 1s1

3

13

14

15

16

17

IIA Q2. Possible oxidation states of Sn? IIIA IVA VA VIA V I I A 4

Li Be 2s1 2s2 11 12

13

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

12 Al 2 1 IIB 3s 3p

19 20 21

22

23

24

25

26

27

28

29

30

31

K Ca Sc

Ti

V

Cr

Mn Fe

Co

Ni

Cu

Zn

Ga Ge

32

1 10 2 10 4s1 4s2 4s23d1 4s23d2 4s23d3 4s13d5 4s23d5 4s23d6 4s23d7 4s23d8 4s 3d 4s 3d 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

1 10 2 10 5s1 5s2 5s24d125s24d2 5s24d3 5s14d5 5s23d5 5s14d7 5s14d8 4d10 5s 4d 5s 4d 5s25p1 5s25p2 5s25p3 5 5 5 6 5 7 7 2 7 3 74 75 76 77 78 79 80 81 82 83 84 Cs Ba L a * Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po 1 10 2 10 6s1 6s2 6s25d1 6s25d2 6s25d3 6s25d4 6s24d5 6s25d6 5d76s2 6s15d9 6s 5d 6s 5d 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#

+

+

+

+

+

2 2 2 3 2 4 2 5 2 6 7 2 7s1 7s2 7s26d1 7s 6d 7s 7d 7s 6d 7s 3d 6s 6d 6d 7s

but no official name assigned

Transition Metals Q. Maximum oxidation state vs. family # ?

1 1A 1

H 2 1s1 IIA 3

18 VIIIA

13 14 15 16 17 IIIA IVA VA VIA VIIA

4

Li Be 2s1 2s2

+2 !

11 12

+3 + 4 + 5 +6 +7

3s1 3s2

IIIB IVB VB VIB VIIB VIIIB " VIIIB IB

Na Mg 3

19 20 21

K Ca Sc

+2 ! 4

22

Ti

+2 +2 ! ! 5

23

V

6

24

Cr

+2 ! 7

25

8 26

Mn Fe

+2 9

27

Co

10 28

Ni

+1 +2 11 29

13

Al

12

IIB 3s2 3p1 30

31

Cu Zn

Ga

32

Ge

1 10 2 10 4s1 4s2 4s2 3d1 4s2 3d2 4s2 3d3 4s1 3d5 4s2 3d5 4s2 3d6 4s2 3d7 4s2 3d8 4s 3d 4s 3d 4s2 4p1 4s2 4p2 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 1

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

VIIIA

Family A Metals

10

Cd 2

10

In

Sn

Sb

5s1 5s2 5s2 4d125s2 4d2 5s2 4d3 5s1 4d5 5s2 3d5 5s1 4d7 5s1 4d8 4d10 5s 4d 5s 4d 5s2 5p1 5s2 5p2 5s2 5p3 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 1 5d10 6s2 5d10 2 2 2 3 2 4 2 5 2 6 7 2 1 9 6s 2 1 2 2 2 3 2 6p4 1 2 2 1 6s 5d 6s 5d 6s 5d 6s 4d 6s 5d 5d 6s 6s 5d 6s 6p 6s 6p 6s 6p 6s 6s 6s 6s 5d 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 7s2 6d1 7s2 6d2 7s2 7d3 7s2 6d4 7s2 3d5 6s2 6d6 6d7 7s2

3

Strength of Redox Agents Example: 2 Na +

Cl2

→ 2 Νa+ + 2 Cl-

RA OA OA RA _________________________________________

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

2 Sb + 3 Cl2 RA

→ 2 Sb3+ + 6 ClOA

OA

RA

 The reactants are the stronger RA

and OA and react spontaneously  The non-reactive products are the weaker OA and RA. RA: Na > Cl-

-

Sb >___ Cl OA strength: ___ Cl2 >___ Sb 3+ RA strength:___

OA: Cl2 > Na+

Reaction and Redox Strength If RA: Cu > Ag

Reactions and Redox Strength  The stronger RA and OA react:

OA: Ag+ > Cu2+

Reactants

Cu(s) + Ag+ (aq) →

reaction

 The weaker RA and OA do NOT react:

Cu(s) + Ag+(aq) → ?

Ag(s) + Cu2+(aq) → ? DEMO

Ag(s) + Cu2+(aq) → no reaction

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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 for Part 1B.  Create a table for recording data (pre-lab). •Zn2+

•Cu2+

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 and Data Analysis  Test available metal and metal ion combinations  Record observations

•Mg2+

•Zn

Example:

•Cu •Mg Reducing agent species (metals) on one side and oxidizing agents species (metal ions) on other side.

Zn(s) + Cu2+ (aq) →

reaction

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Data Analysis

Check data. Does it make sense? Zn2+

Cu2+

# rxns.

Rxn

1 1

Zn Cu

Rxn

# rxns.

1

1

•Zn2+

•Cu2+

•Zn

No

•Reaction

•1

•Cu

•No

No

•0

•0

•1

•# rxns.

“ These results don’t make sense!”

•# rxns.

This data makes sense:  The stronger RA and OA show more reactions!  RA and OA strength are inverse:

 Only one combination of metal and metal ion should react spontaneously -- the stronger RA and OA!

Reducing Agent Strength of Mg, Zn, and Cu? Q1. Complete the table below.

•Zn •Cu •Mg

•Zn2+

•Cu2+

•Mg2+

No

•Rxn.

•No

•No

No

•No

Rxn

Rxn

No

RA: Zn > Cu OA: Cu2+ > Zn2+

Part I A. Metal reactions with water. • Rank the reducing agent strength of the metals Na, K, Mg, and Ca from experimental observations. • Correlate the results with the position of the metal in the periodic table.

Q2. Comparative RA strength of the metals? RA strength: _______________ Mg > Zn > Cu

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Reactivity of K and Na

Experimental Comparison of Ca and Mg Metal + Water → metal hydroxide + H2(g) RA OA OA RA

 Experimental determination of the reactivity of K and Na compared to Ca and Mg.

Example:

Mg(s) + 2HOH(l) → Mg(OH)2(s) +

H2(g)

DEMO

DEMO

Ca > Mg RA: ________________

Experimental Comparison of K, Na, Ca, and Mg

RA and OA Predictions from Electronegativity values = Electron pulling power of an atom when part of a bond Electronegativity of the elements 1 2 3 4 5 6 7 8 IA IIA IIIB IVB VB VIB VIIB

Na skitters around the water surface

K skitters around the water surface and ignites

RA: K > Na > Ca > Mg

H 2.1 Li 1.0 Na 0.9 K 0.8 Rb 0.8 Cs 0.7 Fr 0.7

Be 1.5 Mg 1.2 Ca 1.0 Sr 1.0 Ba 0.9 Ra 0.9

Sc 1.3 Y 1.2 La -Lu Ac 1.1

= Metalloids

Ti 1.5 Zr 1.4 Hf 1.3 Th 1.3

V 1.6 Nb 1.6 Ta 1.5 Pa 1.5

Cr 1.6 Mo 1.8 W 1.7 U 1.7

Mn 1.5 Tc 1.9 Re 1.9 Np-

= Nonmetals

Fe 1.8 Ru 2.2 Os 2.2 No 1.3

9

10

VIIIB

Co 1.8 Rh 2.2 Ir 2.2

Ni 1.8 Pd 2.2 Pt 2.2

11 IB

Cu 1.9 Ag 1.9 Au 2.4

12 13 14 15 16 17 IIB IIIA IVA VA VIA VIIA

Zn 1.6 Cd 1.7 Hg 1.9

B 2.0 Al 1.5 Ga 1.6 In 1.7 Tl 1.8

C 2.5 Si 1.8 Ge 1.8 Sn 1.8 Pb 1.8

N 3.0 P 2.1 As 2.0 Sb 1.9 Bi 1.9

O 3.5 S 2.5 Se 2.4 Te 2.1 Po 2.0

F 4.0 Cl 3.0 Br 2.8 I 2.5 At 2.2

= Metals

7

Q. Predict the RA strength of K compared to Na, Mg,

Q. Where are the best reducing and oxidizing agents located?

and Ca based on position and electronegativity values. IA

IIA

IIIB IVB VB

VIB VIIB

H 2.1 Li Be 1.0 1.5 Na Mg 0.9 1.2 K Ca Sc Ti V Cr Mn Fe 0.8 1.0 1.3 1.5 1.6 1.6 1.5 1.8 Rb Sr Y Zr Nb Mo Tc Ru 0.8 1.0 1.2 1.4 1.6 1.8 1.9 2.2 Cs Ba La Hf Ta W Re Os 0.7 0.9 -Lu 1.3 1.5 1.7 1.9 2.2 Fr Ra Ac Th Pa U Np- No 0.7 0.9 1.1 1.3 1.5 1.7 1.3 ____> _____ > _____ > _____

IB

VIIIB

Co 1.8 Rh 2.2 Ir 2.2

Ni 1.8 Pd 2.2 Pt 2.2

Cu 1.9 Ag 1.9 Au 2.4

IIB

Zn 1.6 Cd 1.7 Hg 1.9

IIIA

B 2.0 Al 1.5 Ga 1.6 In 1.7 Tl 1.8

IVA VA

C 2.5 Si 1.8 Ge 1.8 Sn 1.8 Pb 1.8

N 3.0 P 2.1 As 2.0 Sb 1.9 Bi 1.9

VIA VIIA

O

F

S 2.5 Se 2.4 Te 2.1 Po 2.0

Cl 3.0 Br 2.8 I 2.5 At 2.2

3.5 4.0

K > Na > Ca > Mg

IA

IIA

H 2.1 Li 1.0 Na 0.9 K 0.8 Rb 0.8 Cs 0.7 Fr 0.7

Be 1.5 Mg 1.2 Ca 1.0 Sr 1.0 Ba 0.9 Ra 0.9

IIIB

Sc 1.3 Y 1.2 La -Lu Ac 1.1

IVB

Ti 1.5 Zr 1.4 Hf 1.3 Th 1.3

VB

V 1.6 Nb 1.6 Ta 1.5 Pa 1.5

VIB

Cr 1.6 Mo 1.8 W 1.7 U 1.7

VIIB

Mn 1.5 Tc 1.9 Re 1.9 Np-

IB

VIIIB

Fe 1.8 Ru 2.2 Os 2.2 No 1.3

Co 1.8 Rh 2.2 Ir 2.2

Ni 1.8 Pd 2.2 Pt 2.2

Cu 1.9 Ag 1.9 Au 2.4

IIB

IIIA

IVA

VA

VIA

VIIA

C 2.5 Si 1.8 Ge 1.8 Sn 1.8 Pb 1.8

N 3.0 P 2.1 As 2.0 Sb 1.9 Bi 1.9

O

F

Zn 1.6 Cd 1.7 Hg 1.9

B 2.0 Al 1.5 Ga 1.6 In 1.7 Tl 1.8

3.5 S 2.5 Se 2.4 Te 2.1 Po 2.0

Cl 3.0 Br 2.8 I 2.5 At 2.2

4.0

Caution: Attraction of metal or nonmetal ion for electrons in a bond is different from its metal or nonmetal element.

Questions? Contact [email protected]

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