OBSERVATIONS & CHEMICAL REACTIONS
(Reference:  CH111 General Chemistry I Laboratory Manual, Department of Chemistry , Michigan Technological University, Wiley, 1998)
 

PREPARATION

Note:  I might set this up in stations around the room for less mess.

Lots of test tubes for everyone
50mL         1.0 - 0.1 M KSCN
50mL         1.0 - 0.1 M FeCl3
50mL         1.0 - 0.1 M KMnO4
50mL         3 or 6 M HNO3
30 ribbons  Mg solid
50 mL        1.0 - 0.1 M CuSO4
50 mL        3 or 6 NH4OH
50 mL        1.0 - 0.1 M BaCl2
50 mL        3 or 6 HCl
30 strips     Zn solid
 
 

BACKGROUND

Today we are going to look at several chemical reactions.  You will know that a chemical reaction has taken place because one of the following changes will occur when the reactants are combined:
 •  Change in color
 •  Gas evolution
 •  Temperature change
 •  Production of light or sound
 •  Formation of a precipitate

When substances undergo chemical reactions, their physical properties change and a new substance is created.  Examples of a substance’s physical properties are:
 •  Color
 •  Appearance
 •  Melting or boiling points
 •  State
 •  Density

In order to detect the chemical reaction you will need to use all of your senses (except taste, of course!) To detect these things you will need to look at the test tube, listen for gas evolution, carefully smell if vapor is produced, and touch the test tube to detect a temperature change.  In addition to predicting the products and balancing each equation, you will want to carefully observe and record:
(1) The physical properties of the reactants,
(2) The chemical reaction that has occurred, and
(3) The physical properties of the products.
 

PROCEDURE

· Make sure to label your test tubes in each step, numerically, so you can keep track of which reaction you are observing.
· Predict products and balance each equation, for steps 1, 3a, 4, and 5.

(1)   KSCN(aq)    + FeCl3 (aq)
Combine 20 drops of KSCN and 2 drops FeCl3

 
Describe Reactants Describe Chemical Change Describe Products

 0
0 0
 
(2)   KMnO4 (aq) +  HNO3 (aq) + Mg (s) 
Combine 20 drops of KMnO4 and 5 drops HNO3 then add 2 strips Mg
 
Describe Reactants Describe Chemical Change Describe Products
 
 0
0 0
 
(3a)   CuSO4 (aq)     + NH4OH (aq)
Combine 20 drops of CuSO4 and 1 drop NH4OH
 
Describe Reactants Describe Chemical Change Describe Products
0
 o
0o 0o
 
(3b)   Step 3a     +     NH4OH (aq) 
Combine Step 3a and 4 more drops NH4OH
 
Describe Reactants Describe Chemical Change Describe Products
0
 
0 0
 
(4)   CuSO4 (aq)  + BaCl2 (aq) 
Combine 20 drops of CuSO4 and 2 drops BaCl2
 
Describe Reactants Describe Chemical Change Describe Products
 
 o
o o
 
(5)   HCl (aq)   + Zn (s) 
Combine 20 drops of  HCl and 1 Zn piece
 
Describe Reactants Describe Chemical Change Describe Products
 
 o
o o
 

QUESTIONS

(1) Describe the physical characteristics of the product in step 1.
 
 
 
 

(2) In step 5, was the change a physical change or a chemical reaction?
 
 
 
 

(3) What is an exothermic reaction, and in which (if any) steps did one occur?
 
 
 
 

(4)  What is an endothermic reaction, and in which steps (if any) did one occur?
 
 
 
 

(5)  What is a precipitate, and in which steps (if any) was one formed?
 
 
 
 

DISPOSAL
 

  • All extra solutions and solids can be saved.
  • Unreacted metals can be rinsed and disposed of in trash.
  • Student solutions can all go down the drain.

  •  

     
     
     

    Ginger Chateauneuf, 2000.
     

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