Nick DiPreta
Mr. Cimonello
Due: 3/6/10
CHEMICAL DROP OUTS
Pre lab: Most chemical reactions take place in a solution. Solid chemicals react
quicker when dissolved than as solids. In this experiment, we saw some dissolbed
chemicals react when solutions are combined. New substance may be produced
that have low solubility and drop out of solution. In a chemical reaction, the
substances that react are called the reactants and the substances that are
produced are called the products. The substances that fall out of solutions as
solids are called precipitates.
Purpose: The purpose of this experiment is to combine chemicals to see what
new substances are created and if they dissolve or come together to form
precipitates.
Equipment/Materials- microplate, solutions of barium chloride, magnesium
nitrate, potassium hydroxide, copper sulfate, sodium carbonate
Procedure
1. Obtain solutions of chemicals listed above, each contained in a separate
dropping bottle.
2. Put 5 drops of sodium carbonate solution into a well in the microplate. Add
drops of barium chloride solution. Record you observations in the Data Chart.
3.Using nine separate wells make all the combinations listed in the Data Chart.
Use 5 drops of each solution as you did in step 2. Record your observations in the
Data chart as soon as you make a combination.
4. Write the word equation in the Equation Chart for each combination in which
you see a precipitate form.
5. Look up the name of each possible new substance in the Table of Solubillities
in Water, Found in the Appendix of your lab book. Place an arrow pointing
downward, in the equation after the name of the product of low solubility. The
arrow shows that the compound has dropped out as a precipitate.
Questions
1. Suppose you have unmarked bottles of water, sodium carbonate, and barium
chloride. Could you tell which was which by looking at the bottle?
No, both solutions are soluble, so nothing would have settled to the bottom of
each solution. Thus, each solution would look similar, and no residue would settle
at the bottom.
2. How would you tell the difference between unmarked bottles of barium
chloride and potassium hydroxide?
Potassium hydroxide is a very strong base. One could take a sample of the
substance test its acidity with the ph paper. If it turns dark blue, then we know
that it is KOH because that means that it (the solution) is basic.
3. Look at the table of Solubillities in Water. Which of the possible reactants
always form soluble combinations?
None of the possible reactants always form soluble combinations. For that
to be so, you would need to have a reactant with two soluble parts to it.
For example, sodium nitrate would always be soluble no matter what it is
combined with.
4. Silver nitrate forms a colorless solution. So does ammonium nitrate. How do
you prove that a colorless solution was silver nitrate instead of ammonium
nitrate?
If you combine each solution with sodium hydroxide, the silver nitrate will
combine with it and will not dissolve; the silver combined with hydroxide
will be insoluble. The ammonium nitrate combine and both parts
combined will be soluble.
Conclusion:
It is possible to test if a substance is soluble or not by combining it with other
substances. If we know the solubility rules, it is also easy to predict and
create ways to determine which solution is which if you have two unlabeled
solutions (such as in question 4).