Types of Reactions (Demonstration)

Replacement Reactions : Ionic Reactions

Allows students to visualize a chemical change and can also illustrate conservation of mass (if you want to mass the substances before and after)

Safety goggles should be worn by demonstrator

.01 - .1 M AgNO3   &   NaCl  solutions
Zinc strip   &   .1 M CuSO4 solution
Copper   &   .1 M AgNO3 solution
.01 - .1 M PbNO3   &   KI solutions


Reaction 1 or Reaction 4:
1. Fill 1 large culture tube with solutions so that students see they are
both clear and colorless
2. Prepare another tube (pre-combined) so the precipitate has had a chance to settle
3. Combine 2 more tubes 1/3 full of each into 1 tube so students can see the reaction occur

Reaction 2 or Reaction 3:
1. Fill 250 or 400 mL beaker  (or large culture tube) with solution
2. In front of students add metal strip after observations about both metal and solution have been made

Leave tubes out so student can examine changes.

Describe reactions, 2 & 3 are metal displacement reactions (referred to in their text as Replacement Reactions), where an elemental metal displaces the metal ion in solution.  Can explain also that this is a spontaneous process because the elements/ions relative positions on the activity series.  Reactions 3 & 4 are precipitation reactions (referred to as Ionic) where there is a formation of an insoluable product upon combination of the two solutions.  Can explain relation to soluability rules AgCl is insoluable in water as is PbI2.  They may ask where the water came from, explain that the original solutions are called such because they are made in water, hence the (aq) subscript in the equation.  Show balanced equations also.

 AgNO3 (aq)  + NaCl (aq)   AgCl (s)  +  NaNO3 (aq)

 Zn (s)  +  CuSO4 (aq)   Cu (s)  +  ZnSO4 (aq)

 Cu (s)  +  2AgNO3 (aq)   2Ag (s)  +  Cu(NO3)2 (aq)

 Pb(NO3)2 (aq)  +  2KI(aq)   PbI2 (s)  +  2KNO3

Reaction 1:  For very small quantities can rinse down drain, otherwise follow Flinn guidelines.
Reactions 2&3:  Drain solution, remove metal from tube, rinse well, and dispose of in trash can as solid waste.
Reaction 4:  Drain solution, remove solid, allow to dry, follow Flinn guidelines

Ginger Chateauneuf, 2000.