Halogens (Family VIIA) used in Parts 2 and 3
Experiment Three
1
1A
1
H
 Lab one: Parts 1 and 2A
VIIIA
3
4
2s1
2s2
11
12
3s1
19
3s2
20
4s1
37
4s2 4 s2 3d1 4 s2 3d2 4 s2 3d3 4 s1 3d5 4 s2 3d5 4 s2 3d6 4 s2 3d7 4 s2 3d8 4s 3d
38 39
40
41
42
43
44
45
46
47
5s1
55
5s2 5 s2 4d1 5 s2 4d2 5 s2 4d3 5 s1 4d5 5 s2 4d5 5 s1 4d7 5 s1 4d8 4d1 0 5s 4d 4d 5s 5 s2 5 p1 5 s2 5 p2 5 s2 5 p3 5 s2 5 p4 5 s2 5 p5 5 s2 5 p6
56 57
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Ba La* Hf Ta W Re Os Ir
Pt Au Hg Tl Pb Bi Po At Rn
1 10
10 2
6s2 6 s2 5d1 6 s2 5d2 6 s2 5d3 6 s2 5d4 6 s2 5d5 6 s2 5d6 6 s2 5d7 6 s1 5d9 6s 5d 5d 6s 6 s2 6 p1 6 s2 6 p2 6 s2 6 p3 6 s2 6 p4 6 s2 6 p5 6 s2 6 p6
K
Cs
6s1
87
Fr
7s1
Chlorine
Cl2(g)
Bromine
Br2(l)
Increasing molecular weight
Iodine
I2(s)
15
16
17
5
B
6
C
7
N
8
He
9
O
10
F
1 s2
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
21
29
30
1
10 3d1 04 s2
Ca Sc
Y
22
Ti
Zr
23
V
Nb
24
Cr
25
26
Mn Fe
Mo Tc
Ru
27
Co
Rh
28
Ni
Pd
Ag
89
Ra Ac#
104 105
+
+
106 107 108
+
+
+
109
+
13
14
15
16
17
18
31
32
33
34
35
36
12 Al Si P
S
Cl Ar
IIB 3 s2 3 p1 3 s2 3 p2 3 s2 3 p3 3 s2 3 p4 3 s2 3 p5 3 s2 3 p6
Cu
1
88
14
IIIA IVA VA VIA VIIA
Answer: 0 or -1
Be
Rb Sr
13
2
1 s1
Na Mg
Halogens used in Parts 2 and 3
Q. Possible oxidation states?
2
IIA
Li
 Lab two: Parts 2B and 3
18
10
Zn
48
Cd
10
Ga
49
2
Ge
As
Se
Br
Kr
4 s2 4 p1 4 s2 4 p2 4 s2 4 p3 4 s2 4 p4 4 s2 4 p5 4 s2 4 p6
In
50
Sn
51
Sb
52
Te
53
I
54
Xe
+ Element
synthesized,
but no official name assigned
7s2 7 s2 6d1 7 s2 6d2 7 s2 6d3 7 s2 6d4 7 s2 6d5 7 s2 6d6 7 s2 6d7
HALOGENS
Cl2 = Chlorine
Exist as diatomic NONPOLAR molecules
Oxidation state = zero
Oxidizing agents that react to form halides:
Cl2 + 2 e- → 2 Cl-
1
HALIDES
Halogens (Parts 2 and 3)
 The halogens will be provided in water solution.
Cl- in NaCl(s)
 Exist as anions in salts
 Salt names end in ide (e.g., sodium bromide…)
 Oxidation state = -1.
 Reducing agents
Halides (Parts 2 and 3)
 The halides are provided as sodium salts in water
solution.
Sodium halide (s)
Chlorine water
Bromine water
Iodine water
similar in visual appearance
Part 2A. Color and Solubility of the Halides and Halogens
 Determine and compare the color and
solubility of the halides and halogens in water
and hexane.
Sodium halide (aq)
The sodium salts of the halides visually look the same
in the solid state and in aqueous solution.
2
Color of the Halogens
Solvent Polarity Reminders
 The color of the halogens is solvent dependent.
Example
 Polar (e.g., water) and non-polar (e.g., hexane)
liquids are immiscible.
 Polar and non-polar liquids form separate phases:
Iodine versus Iodine water (dilute and more concentrated)
DEMO
DEMO
DEMO
Salt Solubility Reminders

Salts are soluble and dissociate in polar solvents.
 Salts are NOT soluble and do not dissociate in non-
Q. A yellow-brown aqueous solution contains an
unidentified halogen. If hexane is added to the solution
two phases form where the upper phase is pink and the
lower phase colorless. Identify the halogen
polar solvents.
+ hexane →
“Like attracts like”
DEMO
DEMO
Iodine
Answer:____________
3
Part 2B. Reactivity of the Halogens and Halides.
OA Strength of Chlorine versus Bromine?
 Collect experimental data on the reactivity of the
•Cl-
halogens and halides.
•Br-
•# rxns.
See
expanded
Table, p.77
•Cl2
•Br2
•# rxns.
Table: Oxidizing agents on one side and
reducing agents on the other side.
Discussion questions 3 and 4, p.96
Caution: Check data. Does it make sense?
ClCl2
Br-
# rxns.
No rxn
0
Br2 No rxn
# rxns.
0
Interpreting Experiment Results
1) Cl2 +
OA
0
0
2)
Br2 +
2 Br- → 2 Cl- + Br2
RA
2
RA
Cl-
→ 2
Br-
OA
+ Cl2
 “Reaction 1) or 2) should occur!”
“ These results don’t make sense!”
1) OA strength: Cl
___
Br2
2 >___
One combination of halogen and halide should react
-- the stronger OA and RA agent!
Br2 >___
Cl2
2) OA strength: ___
4
Q. The electronegativity of chlorine = 3.0 and bromine = 2.8.
Experiment Results
Based strictly on electronegativity values, will
Br2 (aq) + NaCl(aq) react?
Q. Br2 (aq) + NaCl (aq) → reaction or no reaction?
 List the Oxidizing and reducing agent species and
indicate the comparative strength
Oxidizing Agent
Reducing Agent
Cl2
Cl-
Br2
Br-
DEMO
→
Add hexane
Br2 (aq)+ 2 NaCl (aq)
no
reaction
________________
Cl-
No. Br2 and
are the weaker OA and RA.
Answer.________________________________
Part 3. Analysis of Redox Reactions
Interpreting Experiment Results
Q2. Identify the species present in the upper and lower
phases upon addition of hexane to the reaction mixture.
 Identify reactants and spectators in redox reactions.
- Non-reactive redox species (K+, Na+ , NO3- ) make
Br2
Na+
Cl -
→
good substitutes for an omitted species in tests.
 Identify products; write a net reaction
- Compare properties to known substances
- use the CRC Handbook.
Add hexane
Br2 (aq)+ 2 NaCl (aq)
no reaction
 Rank the oxidizing or reducing agent strength of
species in the reaction
5
Example: I2 + SnCl2 →
?
Analysis of Reaction
1. Record Observations
“Help. I spilled Iodine!”
DEMO: Add
tin(II) chloride to
iodine spot!
SnCl2(aq) +
I2(aq)
→
clear and
colorless
product
2. Design and Interpret Reference Blank Tests
2. Design and Interpret Reference Blank Tests
Reaction: SnCl2(aq)
Reaction: SnCl2(aq)
+
I2(aq)
→ ?
Reference Blank Test:
NaCl(aq) +
I2(aq)
Conclusion:
“Sn2+ is
a reactant”.
+
I2(aq)
→ ?
Reference Blank Test:
no reaction
DEMO
Sn(NO3)2(aq) +
I2(aq)
reaction
Conclusion:
“Cl- is a spectator”.
6
3) Identify OA and RA Reactants
4) Identify Products and Write a Net Reaction
Q. Identify the oxidizing and reducing agent
reactants:
Sn2+(aq) + I2(aq) →
Observation: Light brown I2(aq) color fades.
?
Knowledge: Sn2+ is the reducing agent.
RA
OA
______________
Sn2+(aq) + I2(aq) →
5). Strength of the Reducing and Oxidizing Agents?
Sn2+aq) +
I2(aq) →
Sn4+ (aq) + 2I - (aq)
RA
OA
OA
RA
2I-(aq) + Sn4+(aq)
_______________
Q. Identify the reactants in the redox reaction,
CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
List the species and indicate OA and RA strength:
Sn2+ >___
I- OA strength: ___
I2 >___
Sn4+
RA strength: ____
OA
F2
“The reactants are the stronger OA and RA”.
RA
__
Co3+
__
Br2
__
K+
__
7
Q. Identify the reactants in the redox reaction,
CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
List the species and indicate OA and RA strength:
OA
F2
RA
F-
Co3+
Co2+
Br2
Br-
K+
K
Q. Identify the reactants in the redox reaction,
CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
 Identify which species will react
OA
F2
RA
F-
Co3+
Co2+
Br2
Br-
K+
K
Q. Identify the reactants in the redox reaction,
CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
 Note (circle) all species present in the reaction.
OA
F2
RA
F-
Co3+
Co2+
Br2
Br-
K+
K
Q. Identify the products in the redox reaction,
CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
OA
F2
RA
F-
Co3+
Co2+
Br2
Br-
K+
K
Answer: Co2+aq) + Br2(aq)
8
Chem 125/126 Exam
Practice exam questions!
You should be able to answer all hourly I exam
questions upon completion of experiment 3.
Exams and review notes on Ctools and course
web site:
http:www.umich.edu/~chem125
9