Analysis of Reactions, E 6

E 6

• Pre-lab report (p.159) 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.

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.

• Design and conduct a minimum of twoquantitative tests and experiments to confirm thatno reaction occurred.

• Do NOT conduct reference blank tests!

SnCl4 (aq) + KI (aq) → ________

DEMO

Clear and colorless

Analysis of A Non-Reaction

Example 1 SnCl4 (aq) + KI (aq) → colorless colorlessQ. Circle any test that can support “no reaction”:A) The temperature of the original solutions and reactionmixture shows no ∆ t°.

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

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

Answer: ________________

Analysis of A Non-Reaction

Q. Why does Test C (SnCl2 + I2 → colorless hexanephase) support “no reaction”?

Test CHexane is colorless and therefore reaction occurrednet rxn: Sn2+ + I2 → Sn4+ + 2 I-

______________________________

SnCl4 + KI → no reaction?

Analysis of a non - reaction

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

DEMO

Q. What tests could you conduct to confirm that “noreaction” has occurred?

Reaction?

Record your qualitative observations of individualreagents and the reagent mixture.

1) Determine the identity of reactants/spectators.

• Record hypothesis, tests, observations, andconclusions.

Reaction 1: Add 20mL 0.10M SnCl2 to 2.0mL of 0.10M Hg(NO3)2

DEMO

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

Analysis of Reactions: Reaction 1

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 test an appropriate test of the hypothesis?

_______

Hypothesis: “Hg2+ is a reactant”.

Identify Reactant and Spectator Species.

Reaction 1: Add 20 mL 0.10 M SnCl2 to 2.0 mL of 0.10M Hg(NO3)2

Test 1 DEMO

Identify Reactant and Spectator Species.

SnCl2 + Na(NO3) → ?_________

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

Test 1:20mL 0.10M SnCl2 to 2.0mL of 0.10M NaNO3 → no reaction

Q. What do the test results tell you about the reaction?

Hypothesis: “Hg2+ is a reactant”.

Identify Reactant and Spectator Species.

___________________

Reaction 1: Add 20mL 0.10M SnCl2 to 2.0mL of 0.10M Hg(NO3)2

Test 2 DEMO

1. Identify Reactant and Spectator Species.

NaCl + Hg(NO3)2 → __________?Q. What do the test results tell you about the reaction?

__________________

2. Reaction Products?

• Compare product properties toknown samples.

• Consult reference texts andcompare listed properties toobserved product properties

• Conduct tests to help confirmproduct ID.

• Write a net reaction.

Product Identification

Reaction: SnCl2 + Hg(NO3)2 → solidTests determine:“The reactants are Hg2+ and Sn2+”.

Q. Based on your knowledge and logic:1. What type of reaction is occurring?2. What is the likely identity of the solid product?

2. _______________1._________.

Product Identification

Reactants: Sn2+ + Hg2+ → solid = ?

Possible oxidation state of reactants:Sn Sn2+ Sn4+

Hg Hg2+

Solid product? = _______

Reaction 2: 0.10 M CuSO4 + HCl (con) → yellow-green solution

DEMO

Q. What type of reaction is likely occurring?

___________________________.

Analysis of Reactions: Reaction 2

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

Team tests:(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?

____________________________DEMO

Design/conduct tests to identify reactants and spectators.

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

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

Team tests:(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?

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

______________________________________

Identify the reaction type.(after confirming reactant identities)

Reactants confirmed: Cu2+

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

Type of reaction?:

__________________________

Identify Products and Write A Net Reaction.

HCl(con) + CuSO4(aq) → yellow-greenColorless blue

________________________________

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

2+ →

Q. How might you further confirm the identity of theproduct and/or show that the product is formed from aLewis acid-base equilibrium reaction)?

Confirm the product identity.

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

Example1. Add a better base such as ________

Confirm the product identity.

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

DEMO

Confirm the product identity.

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

4 NH3

↓

[Cu(NH3)4]2+

+4 H2O Note: Cu2+ bonds with NH3

rather than Cl-.

Example1. Add an acid such as ________

Confirm the product identity.

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

DEMO

Questions?Contact nkerner@umich.edu