halogens - university of michiganchem125/f08/lec06f08e3key.pdf · · 2008-10-13color and...
TRANSCRIPT
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Chem. 125-126: Oct. 8 - Oct. 14
Experiment 3 Session 2 (Three hour lab) Complete Experiment 3 Parts 2B and 3 Complete team report Complete discussion presentation
Part 2A. Color and Solubility of the Halides and HalogensPart 2A. Color and Solubility of the Halides and Halogens
Compare the properties (color and solubility)of the halides and halogens in water andhexane.
11A
18VIIIA
1H1s1
2IIA
13IIIA
14IVA
15VA
16VIA
17VIIA
2He1s2
3Li2s1
4Be2s2
5B
2s22p1
6C
2s22p2
7N
2s22p3
8O
2s22p4
9F
2s22p5
1 0Ne
2s22p6
1 1Na3s1
1 2Mg3s2
3 IIIB
4 IVB
5 VB
6VIB
7VIIB
8VIIIB
9 ⇔
10 VIIIB
11 IB
12 IIB
1 3Al
3s23p1
1 4Si
3s23p2
1 5P
3s23p3
1 6S
3s23p4
1 7Cl
3s23p5
1 8Ar
3s23p6
1 9K4s1
2 0Ca4s2
2 1Sc
4s23d1
2 2Ti
4s23d2
2 3V
4s23d3
2 4Cr
4s13d5
2 5Mn
4s23d5
2 6Fe
4s23d6
2 7Co
4s23d7
2 8Ni
4s23d8
2 9Cu
4s13d10
3 0Zn
3d1 04s2
3 1Ga
4s24p1
3 2Ge
4s24p2
3 3As
4s24p3
3 4Se
4s24p4
3 5Br
4s24p5
3 6Kr
4s24p6
3 7Rb5s1
3 8Sr5s2
3 9Y
5s24d1
4 0Zr
5s24d2
4 1Nb
5s24d3
4 2Mo
5s14d5
4 3Tc
5s24d5
4 4Ru
5s14d7
4 5Rh
5s14d8
4 6Pd
4d10
4 7Ag
5s14d10
4 8Cd
4d1 05s2
4 9In
5s25p1
5 0Sn
5s25p2
5 1Sb
5s25p3
5 2Te
5s25p4
5 3I
5s25p5
5 4Xe
5s25p6
5 5Cs6s1
5 6Ba6s2
5 7La*
6s25d1
7 2Hf
6s25d2
7 3Ta
6s25d3
7 4W
6s25d4
7 5Re
6s25d5
7 6Os
6s25d6
7 7Ir
6s25d7
7 8Pt
6s15d9
7 9Au
6s15d10
8 0Hg
5d1 06s2
8 1Tl
6s26p1
8 2Pb
6s26p2
8 3Bi
6s26p3
8 4Po
6s26p4
8 5At
6s26p5
8 6Rn
6s26p6
8 7Fr7s1
8 8Ra7s2
8 9Ac#
7s26d1
1 0 4 +
7s26d2
1 0 5 +7s26d3
1 0 6 +7s26d4
1 0 7 +7s26d5
1 0 8 +7s26d6
1 0 9 +7s26d7
+ Element synthesized,but no official name assigned
Halogens (Family VIIA)
Q. Possible oxidation states?
Answer: 0 or -1
HalogensHalogens
Chlorine Bromine Iodine
Cl2(g) Br2(l) I2(s)
Increasing molecular weight
HALOGENSHALOGENS
Cl2 = ChlorineExist as diatomic NONPOLAR molecules
Oxidation state = zeroOxidizing agents that react to form halides:
Cl2 + 2 e- → 2 Cl-
HalogensHalogens
The halogens will be available in water solution.
Chlorine water Bromine water Iodine water
• It is difficult to visually distinguish betweenbromine and iodine water.
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Color of the HalogensColor of the Halogens
The color of the halogens is solvent dependent.
Example
Iodine water Iodine in hexane
DEMO
• It is possible to visually distinguish between thehalogens in hexane where each has distinct colors
HALIDESHALIDES
Cl- in NaCl(s)
Exist as anions in salts
Salt names end in ide (e.g., sodium bromide…) Oxidation state = -1.
Reducing agents
HalidesHalides
Sodium halide (s) Sodium halide (aq)
The halides are provided as sodium salts in watersolution.
The sodium salts of the halides visually look thesame in the solid state and in aqueous solution.
Salt Solubility RemindersSalt Solubility Reminders
“Like attracts like”
Salts (e.g., halide salts):• are soluble in polar solvents (e.g., water). are NOT soluble in non-polar solvents (e.g.,hexane).
DEMO
Part 2B. Reactivity of the Halogens and Halides.Part 2B. Reactivity of the Halogens and Halides.
Collect experimental data on the reactivity: - oxidizing agent strength of the halogens - reducing agent strength of the halides.
Discussion questions 3 and 4, p.104
Compare the halogen reactivity data versus:
- periodic table position - electronegativity values
OA Strength of Chlorine versus Bromine?OA Strength of Chlorine versus Bromine?
NO•Br2
NO•Cl2
•Br-•Cl-
Table: Oxidizing agents on one side andreducing agents on the other side.
SeeexpandedTable 5,p.84
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Caution: Check data. Does it make sense?Caution: Check data. Does it make sense?
NONoBr2
NoNOCl2
Br-Cl-
“ These results don’t make sense!”
One combination of halogen and halide should react-- the stronger OA and RA agent!
Interpreting Experiment ResultsInterpreting Experiment Results
1) Cl2 + 2 Br- → 2 Cl- + Br2 RA OA
1) OA strength: ___ >___
2) OA strength: ___ >___
OA RA
Cl2 Br2
2) Br2 + 2 Cl- → 2 Br- + Cl2
Br2 Cl2
“Reaction 1) or 2) should occur!”
IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IVA VA VIA VIIA H 2.1
Li 1.0
Be 1.5
B 2.0
C 2.5
N 3.0
O 3.5
F 4.0
Na 0.9
Mg 1.2
Al 1.5
Si 1.8
P 2.1
S 2.5
Cl 3.0
K 0.8
Ca 1.0
Sc 1.3
Ti 1.5
V 1.6
Cr 1.6
Mn 1.5
Fe 1.8
Co 1.8
Ni 1.8
Cu 1.9
Zn 1.6
Ga 1.6
Ge 1.8
As 2.0
Se 2.4
Br 2.8
Rb 0.8
Sr 1.0
Y 1.2
Zr 1.4
Nb 1.6
Mo 1.8
Tc 1.9
Ru 2.2
Rh 2.2
Pd 2.2
Ag 1.9
Cd 1.7
In 1.7
Sn 1.8
Sb 1.9
Te 2.1
I 2.5
Cs 0.7
Ba 0.9
La -Lu
Hf 1.3
Ta 1.5
W 1.7
Re 1.9
Os 2.2
Ir 2.2
Pt 2.2
Au 2.4
Hg 1.9
Tl 1.8
Pb 1.8
Bi 1.9
Po 2.0
At 2.2
Fr 0.7
Ra 0.9
Ac 1.1
Th 1.3
Pa 1.5
U 1.7
Np-
N o 1.3
Q. Based soley on electronegativity values,compare Cl2 and Br2 as oxidizing agents?
OA: ______>_________Cl2 Br2
Q. If Cl2 is a better oxidizing agent thanBr2, should reaction 1) or 2) occur?Q. If Cl2 is a better oxidizing agent thanBr2, should reaction 1) or 2) occur?
1) Cl2 + 2 Br- → 2 Cl- + Br2 RA OA
Answer:______________
OA RA
Reaction 1)
2) Br2 + 2 Cl- → 2 Br- + Cl2
Answer.______________________________
Q. Based on electronegativity values (chlorine = 3.0and bromine = 2.8), will the reaction below occur? Br2(aq) + NaCl(aq) → ?
Br-Br2
Cl-Cl2
Reducing AgentOxidizing Agent
No. Br2 and Cl- are the weaker OA and RA.
List the Oxidizing and reducing agent speciesand indicate the comparative strength
Experiment:Q. Br2 (aq) + NaCl (aq) → rxn or no rxn?Experiment:Q. Br2 (aq) + NaCl (aq) → rxn or no rxn?
→Add hexane
Br2 (aq)+ 2 NaCl (aq) ________________no reaction
DEMO
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Q2. Identify the species present in the upper and lowerphases upon addition of hexane to the reaction mixture.Q2. Identify the species present in the upper and lowerphases upon addition of hexane to the reaction mixture.
Br2
Na+
Cl - →Add hexane
Br2 (aq)+ 2 NaCl (aq) no reaction
Q. Based on the experiment results, rankCl- and Br - as reducing agents.Q. Based on the experiment results, rankCl- and Br - as reducing agents.
→Add hexane
Br2 (aq)+ 2 NaCl (aq) → no reaction
Br - Cl-Answer: ______> _______
Part 3. Analysis of Redox ReactionsPart 3. Analysis of Redox Reactions
Identify reactants and spectators in redox rxns.
- Non-reactive redox species (K+, Na+, NO3- ) make
good substitutes for an omitted species in tests.
Identify products; write a net reaction- Compare products properties to known substances; refer to the CRC Handbook.
Rank the oxidizing or reducing agent strengthof reaction species
“Help. I spilled Iodine!”
Example: I2 + SnCl2 → ?
DEMO: Addtin(II) chloride toiodine spot!
SnCl2(aq) + I2(aq) → clear and colorless
product
Analysis of Reaction1. Record Observations
2. Identify spectator and reactant species.2. Identify spectator and reactant species.
Reaction: SnCl2(aq) + I2(aq) → ?
Reference Blank Test:
NaCl(aq) + I2(aq) no reaction
Conclusion:
“Sn2+
DEMO
is a reactant”.
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Reaction: SnCl2(aq) + I2(aq) → ?
Reference Blank Test:
Sn(NO3)2(aq) + I2(aq) reaction
Conclusion:
“Cl- is a spectator”.
3) Identify reactants that = the oxidizingand reducing agent.3) Identify reactants that = the oxidizingand reducing agent.
Reactants:
Sn2+(aq) + I2(aq)
RA OA_______________________
Reaction: SnCl2(aq) + I2(aq) → ?
4) Identify Products and Write a Net Reaction4) Identify Products and Write a Net Reaction
Observation: Light brown I2(aq) color fades.
I2(aq) → _______________ Sn2+(aq) +
Knowledge: Sn2+ is a reducing agent.
2I-(aq) + Sn4+
(aq)
and thus must form the halide I-
and thus must form Sn4+ (rather than Sn0 )
Sn2+aq) + I2(aq) → Sn4+
(aq) + 2I - (aq)
RA OA OA RA
5). Strength of the Reducing and Oxidizing Agents?
I2 Sn4+Sn2+ I- RA strength: ____ >___ OA strength: ___ >___
“The reactants are the stronger OA and RA”.
List the species and indicate OA and RA strength:
OA F2
Co3+
Br2
K+
Exam Q. Identify the reactants in the reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA __ __ __ __
List the species and indicate OA and RA strength:
OA F2 Co3+ Br2
K+
Q. Identify the reactants in the redox reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA F-
Co2+
Br-
K
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Note (circle) all species actually present in thereaction mixture.
OA F2
Co3+
Br2
K+
Q. Identify the reactants in the redox reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA F-
Co2+
Br-
K
Identify (circle) which species will react based onabove oxidizing agent (OA) strength
OA F2
Co3+
Br2
K+
Q. Identify the reactants in the redox reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA F-
Co2+
Br-
K
OA F2 Co3+ Br2
K+
Q. Identify the products in the redox reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA F-
Co2+
Br-
K
Answer: Co2+aq) + Br2(aq)
Chem 125/126 Hourly I Exam
Practice exam questions!
You should be able to answer all hourly I examquestions upon completion of experiment 3.Exams on Ctools and the course web site:http:www.umich.edu/~chem125