Purpose: The purpose of this laboratory is to identify how many of the possible combinations of two compounds produce a visible reaction by the production of a precipitate. There are six compounds: BaCl2, Ba(NO3)2, Na2CrO4, K2CrO4, NaNO3, and KCl.
Procedure: Combine the six compounds two at a time. This process produces 15 possible combinations. Invert a 400 mL beaker and place two drops from each of the two selected compounds together and watch for a reaction. Record your observations and write balanced equations for those which produced a visible reaction. Examples,
BaCl2 + Ba(NO3)2 --> No Reaction
BaCl2 + K2CrO4 --> BaCrO4 + 2 KCl
Results: This is the section of the lab. report in which the 15 possible combinations should be written showing those which did produce a visible reaction.
Conclusion: This section is dedicated to your summary of the laboratory exercise. Here you explain your observations. Example: In the first sample combination above it could be anticipated that no reaction would occur because both reactants contained the same positively charged Ba++ ion. This is known as the "Common Ion Effect." In the second reaction the visible compound is BaCrO4 which produces a yellow precipitate as generally chromates are insoluble.