Chemical drop outs

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).