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
5
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
6
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]
8