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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