E6
• 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.
Analysis of Reactions, E 6
 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
Example 1:
Ag(s)
+
silver solid
Ag(s) + Co(NO3)2(aq) → ?
Some example of tests or measurements:
Co(NO 3)2(aq) → no visible change
clear red solution
DEMO
Q. What tests or measurements could you conduct to
confirm that “no reaction” has occurred?
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’t
change upon addition of silver. (Use a spectrophotometer
to show no delta in absorbance).
3. Show that the mass of Ag remains constant (Use a
balance)
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 AgNO 3(aq) and get a reaction producing
Ag(s) and Co(NO 3)2(aq).
Analysis of a Non - Reaction
Record your qualitative observations of individual
reagents and the reagent mixture.
• Conduct a minimum of two quantitative tests and
experiments to confirm that no reaction occurred.
• Tests should demonstrate that no change in
reactant properties has occurred.
• Do NOT conduct reference blank tests!
Analysis of A Non-Reaction
Reaction 2
SnCl4 (aq) + KI (aq) → ?
SnCl4 (aq) + KI (aq) →
clear and colorless solutions
DEMO
Clear
and colorless
__________________
SnCl4 + KI
Reaction 2
SnCl4 (aq) + KI (aq) → colorless
colorless
→
no reaction?
Reaction?
Q. Why does Test C support “no reaction”?
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.
Test C: SnCl2 + I 2 = reaction
net rxn: Sn 2+ + I 2 → Sn4+ + 2 I Hexane is colorless ∴ reaction occurred
Note: Rxn being studied: Sn 4+ + Cl
/ - + K/+ + I- → ?
 Record your qualitative observations of
individual reagents and the reagent mixture.
1) Determine the identity of reactants/spectators.
• Record hypothesis, tests, observations, and
conclusions.
If Sn 4+ + I - react the products = Sn 2+ + I 2
Sn4+ + I - are the products of a spontaneous
redox reaction and thus do not react.
Answer: A) and C)
Analysis of Reactions
Identify Reactant and Spectator Species
Reaction:
Add 20mL 0.10M SnCl 2 to 2.0mL of 0.10M Hg(NO 3)2
Record Observations:
Reaction:
Add 20mL 0.10M SnCl 2 to 2.0mL of 0.10M Hg(NO 3)2
Identify Reactant and Spectator Species
Reaction:
SnCl2 + Hg(NO3)2
colorless
white solid
gray-bl solid
Hypothesis: “Hg2+ is a reactant”.
Test 1:
20mL 0.10M SnCl 2 to 2.0mL of 0.10M NaNO 3 → ?
DEMO
Q. Is test 1 an appropriate test of the hypothesis?
SnCl 2 + Hg(NO 3)2→ white ppt. → gray-bl ppt.
Colorless solutions
DEMO
Yes
Test 1:
SnCl2 + Na(NO 3) → _________?
No reaction
Q. What do test 1 results tell you?
Hg2+ is critical to reaction.
Identify Reactant and Spectator Species
Reaction:
SnCl2 + Hg(NO3)2
colorless
white solid
gray-bl solid
Identify Reactant and Spectator Species
Reaction:
Add 20mL 0.10 M SnCl 2 to 2.0 mL of 0.10 M Hg(NO 3)2
white solid
gray-bl solid
DEMO
Test 2:
NaCl + Hg(NO 3)2 → _________?
No reaction
Q. What do test 2 results tell you?
Sn2+ is critical to reaction.
Test 3:
Sn(NO 3) 2 + Hg(NO 3)2 → _________?
gray-bl solid
Q. What do test 3 results tell you?
1. What type of reaction is occurring?
2. What is the likely identity of the solid product?
1. Redox and
ppt. (Lewis acid-base)
2. Sn or Hg = gr-black solid?
• Compare product properties to
known samples.
• Consult reference texts and
compare listed properties to
observed product properties
• Conduct tests to help confirm
product ID.
• Indicate type of reaction
occurring
• Write a net reaction.
Cl - is critical to production of the white solid
Products and Reaction?
Reaction:
SnCl2 + Hg(NO 3)2 → white solid → gr-black solid
Test results:
Reactants = Hg2+ and Sn 2+ (for gr-black solid)
Cl - and ___? (for white solid)
Products and Reaction?
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)
White intermediate insoluble product?
Cl- + (mercury or tin ion) ?
Check CRC Handbook :
HgCl insoluble and white
(SnCl2 and SnCl 4 are soluble)
Products and Reaction
Analysis of Reactions
Reaction:
Add 20mL 0.10M SnCl 2 to 2.0mL of 0.10M Hg(NO 3)2
Identify Reactants and Spectators
Reaction:
0.10 M CuSO 4 + HCl (con) → yellow-green
blue
colorless
Reaction 2:
0.10 M CuSO 4 + HCl (con) → ?
Q. Test that will directly determine if Cl- is a reactant?
→
SnCl 2 + Hg(NO 3)2→ white ppt. → gray-bl ppt.
(HgCl)
(Hg)
Reaction:
0.10 M CuSO 4 + HCl (con) → yellow-green soln
blue
colorless
Q.Test that will directly confirm if SO 42- is a spectator?
(1)Add concentrated HNO 3 to 0.1 M CuSO 4.
→ (2)Add concentrated HCl to 0.1M Cu(NO3)2.
(3) Add concentrated NaCl to 0.1 M CuSO 4.
Q. If the hypothesis is correct, what will you observe
when conducting the test?
The blue solution mixture will turn yellow-green.
DEMO
Q. What type of reaction is likely occurring?
Lewis acid-base
DEMO
Identify Reactants and Type of Reaction
Reactants:
Cu2+(aq) +
(blue)
Cl- (aq) → yellow-green soln
(colorless)
Type of reaction?:
Lewis acid-base (complexation)
(1)Add concentrated HNO 3 to 0.1 M CuSO 4.
(2)Add concentrated HCl to 0.1M Cu(NO 3)2.
(3) Add concentrated NaCl to 0.1 M CuSO 4.
Q. If the hypothesis is correct, what will you observe
when conducting the test?
The solution mixture will remain blue
DEMO
Identify Product/s and Write A Net Rxn
Product
Chloro complex ion of Cu(II)
Q. Complete the net reaction:
_ Cl- + __ [Cu(H2O)4]2+ →
4 Cl- + [Cu(H2O)4]2+ → [Cu(Cl)4]2- + 4 H2O
Confirm Reaction
Confirm Reaction
Confirm Reaction
[Cu(H2O) 4]2+ + 4 Cl - →
[Cu(H2O) 4]2+ + 4 Cl - →
[Cu(Cl)4]2- + 4H2O
Q. How might you further confirm the identity of
the product and/or show that the product is formed
from a Lewis acid-base equilibrium reaction)?
[Cu(H 2O) 4] 2+ + 4 Cl - →
[Cu(Cl)4]2- + 4H 2O
4 NH3
Example 1
NH3
1. Add a better base such as ________
↓
DEMO
Confirm Reaction
[Cu(H2O) 4]2+ + 4 Cl - →
[Cu(Cl)4]2- + 4H2O
+
[Cu(NH3)4]2+
+
4 H2 O
Note: Cu 2+ bonds with
NH3 rather than Cl-.
Confirm Reaction
[Cu(Cl)4]2- + 4H2O
Example 2
Ag+
1. Add an acid such as ________
[Cu(H2O) 4]2+ + 4 Cl - →
+
Ag(H 2O) 2]+
[Cu(Cl)4]2- + 4H2O
↓
DEMO
[Ag(H 2O)Cl]
+
H2O
Cl- bonds
Note:
with
rather than Cu 2+.
Ag +
Questions?
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