Chemical Reactions
What’s in the Bottles?
What’s in the Bottles
• Qualitative Analysis
– Identification
– Not quantitation
– Volumes of reagents not critical
• A basic understanding of doubledisplacement reactions important
Evidences of a Chemical Reaction
• Color change
• Precipitate formation
• Temperature change
• Gas evolution
• Formation of a weak electrolyte
Solubility Rules (abbreviated list)
• Group 1 compounds are soluble
• All nitrates are soluble
• Most chlorides are soluble
– Exceptions are Pb2+, Ag+, Hg22+
• Most sulfates are soluble
– Exceptions are Sr, Ba, Pb, Hg22+
Refer to Lab Manual Appendix 4
for more complete list
Solubility Reactions
KNO3(aq)
H2O
+(aq) + NO -(aq)

K

3
H2O
Cu(NO3)2(aq)
(aq)
2+(aq) + 2 NO 
Cu

3
3 Representations of Chemical Equations
• Whole molecular equation
Pb(NO3)2(aq) + 2 KI(aq)  PbI2(s) + 2 KNO3(aq)
• Whole ionic equation
Pb2+(aq) + 2 NO3-(aq) + 2 K+(aq) + 2 I-(aq)  PbI2(s) + 2 K+(aq) + 2NO3-(aq)
• Net ionic equation
Remove
Pb2+(aq) +the2 spectator
I-(aq)   ions
PbI2(s)
Some notes about this week’s lab
•
•
•
•
•
•
•
Concentrated acids: BE CAREFUL
AgNO3 will stain your skin—wear gloves
All waste must be collected in designated containers
Use well plates
One pipette per bottle please!
Test for temperature change if no other indications
Determine unknowns BEFORE leaving lab
Some notes about this week’s lab
Litmus Paper:
Base turns red paper blue
Acid turns blue paper red
ase
Cute, huh? Aci
lue
Re
B
D
Note: use a glass stir rod to spot the litmus
paper—DO NOT dip litmus into test-tube
Some Example Reactions
Whole molecular reaction (Double-Displacement)
2 AgNO3(aq) + ZnCl2(aq)  Zn(NO3)2 (aq) + 2 AgCl (s)
Will a reaction occur? Write possible products.
Will a precipitate form? Check the solubility rules.
Some Example Reactions
Reagents
AgNO3
Ba(NO3)2
NaOH
HCl
AgNO3 Ba(NO3)2 NaOH
---
NR
---
HCl
Brown White
Solid Solid
NR
NR
---
Temp
Increase
---
Some notes about groups and reports
 Group Dynamics
 It is each members responsibility to make sure that
ALL group members understand the material
 Play well with others!
Some notes about groups and reports
This investigation, Author
1: Introduction and Conclusion
2: Discussion
3: Data/Results and Experimental
This investigation, Author
B: Introduction, Conclusion, Data/Results
A: Discussion and Experimental
Procedure Design Today
You must create complete reaction tables
(chemical equations with expected products,
if any) for 2 of the possible groups (you
choose which).
Note: You must complete the ID of the
bottle group assigned before leaving lab.