E 6 Lab - umich.edu

Analysis of Reactions, E 6

E 6 Lab

• Pre-lab report (p.170) due at the start of lab

Single session two hour lab experiment.

Teams analyze 3 assigned reactions. - one reaction may or may not be a non-reaction.

Team report is due at the end of lab. - report = write up of the analysis of the 3 reactions.

E 6 Discussion

• Present what you did in lab and wrote up for your labreport, regardless of whether it is right or wrong.

• Present what you actually did in LAB, and the logic youused to justify your conclusions.

• If what you did in lab was wrong, explain where you wentwrong and why.

• Present things you could have done better, if any, toanalyze the reaction.

Teams present one of the 3 reactions in discussion during the first hour of the next session.

Analysis of a Non - Reaction

Record your qualitative observations of individualreagents and the reagent mixture.

• Conduct a minimum of two quantitative tests andexperiments to confirm that no reaction occurred.

• Tests should demonstrate that no change inreactant properties has occurred.

• Do NOT conduct reference blank tests!

Analysis of a non - reaction

Ag(s) + Co(NO3)2(aq) → no visible change silver solid clear red solution

Analysis of a non - reaction

Example: Ag(s) + Co(NO3)2(aq) → no visible change silver solid clear red solution

Q. What tests or measurements could you conductto confirm that “no reaction” has occurred?

Ag(s) + Co(NO3)2(aq) → ?

Some example of tests or measurements:1. Show that the pH of Co(NO3)2(aq) doesn’t change upon

addition of silver metal. (Use a pH paper or pH meter)

2. Show that the concentration of Co(NO3)2(aq) doesn’tchange upon addition of silver. (Use a spectrophotometerto show no delta in absorbance).

3. Show that the mass of Ag remains constant (Use abalance)

4. Show that the temperature of Co(NO3)2(aq) doesn’t change(Use a thermometer)

5. Show that the Co(NO3)2(aq) does not contain silver ions(Add a ppt. agent such as NaCl and get no AgCl ppt)

6. Add Co(s) to AgNO3(aq) and get a reaction producingAg(s) and Co(NO3)2(aq).

Co(s) + Ag(NO3)2(aq) → Ag(s) + Co(NO3)2(aq) cobalt solid colorless soln silver solid red soln

Test to Confirm No Reaction

SnCl4 (aq) + KI (aq) → __________________ clear and colorless solutions

DEMO

Clear and colorless

Analysis of A Non-Reaction

Reaction 2 SnCl4 (aq) + KI (aq) → ?

Reaction 2

SnCl4 (aq) + KI (aq) → colorless colorless

Q. Circle any test that can support “no reaction”: A) The temperature of the original solutions and

reaction mixture shows no ∆ t°.

B) KCl (aq) + KI (aq) + hexane → clear, colorless phases

C) SnCl2 (aq) + I2(aq) + hexane → clear, colorless phases.

Answer: A) and C) Sn4+(aq) + 2 I-

(aq) ← I2 (aq) + Sn2+ (aq)

Analysis of A Non-Reaction

Q. Why does Test C support “no reaction”?

Note: Rxn being studied: Sn4+ + Cl- + K+ + I- → ?/ /

Test C: SnCl2 + I2 = reactionnet rxn: Sn2+ + I2 → Sn4+ + 2 I-

Hexane is colorless ∴ SnCl2 + I2 reacted

Sn4++ I- are the products of a spontaneous

redox reaction (Sn2+ + I2) and thus do not react.

SnCl4 + KI → no reaction?

Reaction?

Record your qualitative observations ofindividual reagents and the reagent mixture.

1) Determine the identity of reactants/spectators.

• Record hypothesis, tests, observations, andconclusions.

Analysis of Reactions

Add 20mL 0.10M SnCl2 to 2.0mL of 0.10M Hg(NO3)2→ ______________?

Reaction: Add 20mL 0.10M SnCl2 to 2.0mL of 0.10M Hg(NO3)2

SnCl2 + Hg(NO3)2→ white ppt. → gray-bl ppt.Colorless solutions

Analysis of Reactions

1.Record Observations:

Reaction: Add 20mL 0.10M SnCl2 to 2.0mL of 0.10M Hg(NO3)2

Test :

20mL 0.10M SnCl2 to 2.0mL of 0.10M NaNO3 → ?

Q. Is the above test an appropriate test of thehypothesis?

Yes

Hypothesis: “Hg2+ is a reactant”.

Identify Reactant and Spectator Species

Reaction: SnCl2 + Hg(NO3)2 white solid gray-bl solid colorless

DEMO

Identify Reactant and Spectator Species

Test: SnCl2 + Na(NO3) → _________?No reaction

Q. What do the test results tell you?

Hg2+ is critical to reaction.

Reaction: SnCl2 + Hg(NO3)2 white solid gray-bl solid colorless

DEMO

Identify Reactant and Spectator Species

Test 2: NaCl + Hg(NO3)2 → _________?No reaction

Q. What do test 2 results tell you?

Sn2+ is critical to reaction.

Reaction: Add 20mL 0.10 M SnCl2 to 2.0 mL of 0.10 M Hg(NO3)2

white solid gray-bl solid

Identify Reactant and Spectator Species

Test 3: Sn(NO3)2 + Hg(NO3)2 → _________?gray-bl solid

Q. What do test 3 results tell you?

Cl -is critical to production of the white solid

Reaction Products?

• Compare product properties toknown samples.

• Consult reference texts andcompare listed properties toobserved product properties

• Conduct tests to help confirmproduct ID.

• Indicate type of reactionoccurring

• Write a net reaction.

Products and Reaction?

Reaction:SnCl2 + Hg(NO3)2 → white solid → gr-black solidTest results:Reactants = Hg2+ and Sn2+ (for gr-black solid) Cl- and ___? (for white solid)

1. What type of reaction is occurring?2. What is the likely identity of the solid product?

2. Sn or Hg = gr-black solid?1. Redox andppt. (Lewis acid-base)

Product Identification

Reactants: Sn2+ + Hg2+ → gr-black solid = ?

Possible oxidation state of reactants:Sn Sn2+ Sn4+

Hg Hg2+

Gr-black solid product? = Hg

Products and Reaction

Net redox reaction (gr-bl solid product): Sn2+

(aq) + Hg2+ (aq) → Hg(s) + Sn4+

(aq)

Check CRC Handbook :

White intermediate insoluble product?Cl- + (mercury or tin ion) ?

HgCl insoluble and white(SnCl2 and SnCl4 are soluble)

Reaction:

Add 20mL 0.10M SnCl2 to 2.0mL of 0.10M Hg(NO3)2

SnCl2 + Hg(NO3)2→ white ppt. → gray-bl ppt. (HgCl) (Hg)

Products and Reaction

Reaction 2: 0.10 M CuSO4 + HCl (con) → ?

Analysis of Reactions

Reaction 2: 0.10 M CuSO4 + HCl (con) → _____________?

DEMO

Q. What type of reaction is likely occurring?

Analysis of Reactions

Lewis acid-base

Reaction: 0.10 M CuSO4 + HCl (con) → yellow-green blue colorless

(1)Add concentrated HNO3 to 0.1 M CuSO4.(2)Add concentrated HCl to 0.1M Cu(NO3)2.(3) Add concentrated NaCl to 0.1 M CuSO4.

Q. Test that will directly determine if Cl- is a reactant?

→

The solution mixture will remain blueDEMO

Identify Reactants and Spectators

Q. If the hypothesis is correct, what will you observe when conducting the test?

Reaction 2: 0.10 M CuSO4 + HCl (con) → ?

Analysis of Reactions Reaction: 0.10 M CuSO4 + HCl (con) → yellow-green soln

blue colorless

(1)Add concentrated HNO3 to 0.1 M CuSO4.(2)Add concentrated HCl to 0.1M Cu(NO3)2.(3) Add concentrated NaCl to 0.1 M CuSO4.

Q.Test that will directly confirm if SO42- is a spectator?

→

The blue solution mixture will turn yellow-green.

DEMO

Q. If the hypothesis is correct, what will you observe when conducting the test?

Identify Reactants and Type of Reaction

Reactants: Cu2+

(aq) + Cl- (aq) → yellow-green soln (blue) (colorless)

Type of reaction?:

Lewis acid-base (complexation)

Identify Product/s and Write A Net Rxn

Product

4 Cl- + [Cu(H2O)4]2+ → [Cu(Cl)4]

2- + 4 H2O

Q. Complete the net reaction:_ Cl- + __ [Cu(H2O)4]

2+ →

Chloro complex ion of Cu(II)- Check the list of “common complex ions” orthe CRC Handook for the formula

Q. How might you further confirm the identity ofthe product and/or show that the product is formedfrom a Lewis acid-base equilibrium reaction)?

Confirm Reaction

[Cu(H2O)4]2+ + 4 Cl - → [Cu(Cl)4]2- + 4H2O

Example 11. Add a better base such as ________

Confirm Reaction

[Cu(H2O)4]2+ + 4 Cl - → [Cu(Cl)4]

2- + 4H2O

DEMO

NH3

[Cu(H2O)4]2+ + 4 Cl - → [Cu(Cl)4]

2- + 4H2O

+4 NH3

↓

[Cu(NH3)4]2+

+4 H2O

Note: Cu2+

bonds with NH3rather than Cl-.

Example 21. Add an acid such as ________

Confirm Reaction

[Cu(H2O)4]2+ + 4 Cl - → [Cu(Cl)4]

2- + 4H2O

DEMO

Ag+

[Cu(H2O)4]2+ + 4 Cl - → [Cu(Cl)4]

2- + 4H2O

+ Ag(H2O)2]

+

↓

[Ag(H2O)Cl]+

H2ONote: Cl- bonds with Ag+

rather than Cu2+.