1

Experiment Three

Lab one: Parts 1 and 2A Lab two: Parts 2B and 3

11A

18VIIIA

1H

1s1

2IIA

13

IIIA14

IVA15

VA16

VIA17

VIIA

2He1s2

3Li

2s1

4Be

2s2

5B

2s22p1

6C

2s22p2

7N

2s22p3

8O

2s22p4

9F

2s22p5

1 0Ne

2s22p6

1 1Na

3s1

1 2Mg

3s2

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 9K

4s1

2 0Ca

4s2

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 7Rb

5s1

3 8Sr

5s2

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 5Cs

6s1

5 6Ba

6s2

5 7

La*

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 7Fr

7s1

8 8Ra

7s2

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) used in Parts 2 and 3

Q. Possible oxidation states?

Answer: 0 or -1

Halogens used in Parts 2 and 3

Chlorine Bromine Iodine Cl2(g) Br2(l) I2(s)

Increasing molecular weight

HALOGENS

Cl2 = ChlorineExist as diatomic NONPOLAR moleculesOxidation state = zeroOxidizing agents that react to form halides: Cl2 + 2 e- → 2 Cl-

2

HALIDES

Cl- in NaCl(s)

Exist as anions in salts Salt names end in ide (e.g., sodium bromide…) Oxidation state = -1. Reducing agents

Halogens (Parts 2 and 3)

The halogens will be provided in water solution.

Chlorine water Bromine water Iodine water

similar in visual appearance

Halides (Parts 2 and 3)

Sodium halide (s) Sodium halide (aq)

The halides are provided as sodium salts in watersolution.

The sodium salts of the halides visually look the samein the solid state and in aqueous solution.

Part 2A. Color and Solubility of the Halides and Halogens

Determine and compare the color andsolubility of the halides and halogens in waterand hexane.

3

Color of the Halogens

The color of the halogens is solvent dependent.

Example

Iodine versus Iodine water (dilute and more concentrated)

DEMO

Solvent Polarity Reminders

Polar (e.g., water) and non-polar (e.g., hexane)liquids are immiscible.

DEMO

Polar and non-polar liquids form separate phases:

DEMO

Salt Solubility Reminders

“Like attracts like”

Salts are soluble and dissociate in polar solvents. Salts are NOT soluble and do not dissociate in non-polar solvents.

DEMO

Q. A yellow-brown aqueous solution contains anunidentified halogen. If hexane is added to the solutiontwo phases form where the upper phase is pink and thelower phase colorless. Identify the halogen

Answer:____________DEMO

+ hexane →

Iodine

4

Part 2B. Reactivity of the Halogens and Halides.

Collect experimental data on the reactivity of thehalogens and halides.

Discussion questions 3 and 4, p.96

OA Strength of Chlorine versus Bromine?

•# rxns.•Br2

•Cl2

•# rxns.•Br-•Cl-

Table: Oxidizing agents on one side andreducing agents on the other side.

SeeexpandedTable, p.77

Caution: Check data. Does it make sense?

00# rxns.

0No rxnBr2

0No rxnCl2

# rxns.Br-Cl-

“ These results don’t make sense!”

One combination of halogen and halide should react-- the stronger OA and RA agent!

Interpreting 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!”

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Answer.________________________________

Q. The electronegativity of chlorine = 3.0 and bromine = 2.8. Based strictly on electronegativity values, will Br2(aq) + NaCl(aq) react?

Br-Br2

Cl-Cl2

Reducing AgentOxidizing Agent

No. Br2 and Cl- are the weaker OA and RA.

List the Oxidizing and reducing agent species andindicate the comparative strength

Experiment ResultsQ. Br2 (aq) + NaCl (aq) → reaction or no reaction?

→Add hexane

Br2 (aq)+ 2 NaCl (aq) ________________no reaction

DEMO

Interpreting Experiment ResultsQ2. 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

Part 3. Analysis of Redox Reactions

Identify reactants and spectators in redox reactions.

- Non-reactive redox species (K+, Na+, NO3- ) make

good substitutes for an omitted species in tests.

Identify products; write a net reaction- Compare properties to known substances- use the CRC Handbook.

Rank the oxidizing or reducing agent strength ofspecies in the reaction

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“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. Design and Interpret Reference Blank TestsReaction: SnCl2(aq) + I2(aq) → ?

Reference Blank Test:

NaCl(aq) + I2(aq) no reaction

Conclusion:

“Sn2+ is a reactant”.DEMO

2. Design and Interpret Reference Blank TestsReaction: SnCl2(aq) + I2(aq) → ?

Reference Blank Test:

Sn(NO3)2(aq) + I2(aq) reaction

Conclusion:

“Cl- is a spectator”.

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3) Identify OA and RA Reactants

Q. Identify the oxidizing and reducing agentreactants:

Sn2+(aq) + I2(aq) → ?

RA OA______________

4) Identify Products and Write a Net Reaction

Observation: Light brown I2(aq) color fades.

I2(aq) → _______________ Sn2+(aq) +

Knowledge: Sn2+ is the reducing agent.

2I-(aq) + Sn4+

(aq)

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+

Q. Identify the reactants in the redox reaction,CoF3(aq) + KBr(aq) → ?

given OA Strength: F2 > Co3+ > Br2 > K+

RA __ __ __ __

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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

Note (circle) all species present in the reaction.

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 which species will react

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)

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Chem 125/126 Exam

Practice exam questions!You should be able to answer all hourly I examquestions upon completion of experiment 3.Exams and review notes on Ctools and courseweb site:http:www.umich.edu/~chem125