Chemical Reactions Lab PSI Chemistry

Transcription

1 Chemical Reactions Lab PSI Chemistry Name Purpose: Observe the different types of chemical reactions. Materials: - 6 test tubes - test tube rack M copper(ii)sulfate solution M sodium hydroxide solution M calcium nitrate solution M sodium chloride solution M silver nitrate solution M acetic acid solution (household vinegar) - baking soda - solid potassium chlorate - rubber stopper with hole with glass tube through - rubber hose - collection trough and gas collection jar - transfer pipettes - clear spot plates - bunsen burner - Wooden splint - methyl red indicator PART A: Observing Precipitation reactions. Procedure: 1. Fill 4 test tubes each with 3 ml of 0.3 M copper(ii)sulfate, 0.3 M sodium hydroxide, 0.3 M silver nitrate, and 0.3 M sodium chloride solution. 2. In the space below, write the formulas for any precipitates that could be formed from the combination of the solutions in the test tubes. For each precipitate, write the proper net-ionic equation for it s formation. For each proposed precipitate mix the two solutions using transfer pipettes to mix small quantities of the two solutions in the well of a clear spot plate. Proposed Precipitate Solutions to be mixed Net-Ionic Equation Lab Observations

2 3. Choose two solutions that, when mixed, would NOT form a precipitate and mix them together. Record your observations below in the table. Solutions to be mixed Lab Observations 4. Dispose of all solutions in waste container designated by your instructor and wash glassware. PART B: Observing Oxidation/Reduction reactions. 1. Using a test tube, spatula, and balance, mass out approximately 10 grams of potassium chlorate. Separately, mass out 2 grams of MnO2 catalyst and add to the 10 grams of potassium chlorate in the test tube. Note: The manganese dioxide only acts as a catalyst to speed up the reaction - NOT to participate in it as a reactant. 2. Set up apparatus as shown below in picture. The test-tube must be secure in a utility clamp above the burner. A rubber stopper should be placed in the end of the test - tube with one hole stopper containing glass tube. Rubber hose should be fixed to this end and to the input in the trough. Fill the trough half full with water. Fill the glass collection jar full with water. Cover and flip into position over hole in bottom of trough, remove cover so it is free to receive gas. 3. Heat the potassium chlorate gently and collect oxygen gas until the collection jar is full. Remove heat from the test-tube and shut off burner when finished. The other

3 product of the reaction is potassium chloride. Write the balanced equation for the reaction below and determine the oxidation states of all elements on both the reactant and product side. Oxidation States(Reactants) Oxidation States(Products) K = K = Cl = Cl = O = O = 4. Identify which substance was oxidized? Justify your answer. 5. Identify which substance was reduced? Justify your answer. 6. What type of oxidation/reduction reaction was this (combustion, decomposition, synthesis, disproportionation)? Justify your answer. 7. A common test to verify the presence of oxygen gas is to light a wooden splint and let it burn for a small time. Blow it out, then place it in a bottle full of oxygen gas. The oxygen will react with the splint and the ember should glow very bright indicating a reaction with the oxygen. Perform this test. What did you observe? 8. Dispose of materials as directed by your teacher. PART C: Acid/Base Reactions 1. Pour 10 ml of vinegar (0.88 M acetic acid solution) into an evaporating dish. Add 5 drops of methyl red indicator. It is red in any solution with a ph less than 4. It turns yellow when a solution becomes neutral. Acids have low ph values. What color is your vinegar now? 2. In this reaction, we will neutralize our acidic vinegar (hydrogen acetate) with baking soda (sodium bicarbonate) - a base. The products include water, carbon dioxide, and water. Write the proper balanced reaction below. 3. Which substance lost an H+ ion? Is this classified as an acid or as a base?

4 4. Which product in the reaction indicates this was a neutralization reaction? 5. Add 0.80 grams of baking soda (sodium bicarbonate) to the vinegar in the dish and observe. Write your observations below: 6. What color is your solution now? What does this tell you? 7. Dispose of materials as directed by your teacher. Teacher Guide: PART A: - Small test tubes can be used instead of spot plate.

5 Proposed Precipitate Solutions to be mixed Net-Ionic Equation Lab Observation s AgOH AgNO3 and NaOH Ag+(aq) +OH-(aq) --> AgOH(s) ppt Cu(OH)2 CuSO4 and NaOH Cu2+(aq) +2OH-(aq) --> Cu(OH)2(s) ppt AgCl AgNO3 and NaCl Ag+(aq) + Cl-(aq) --> AgCl(s) ppt PART B: Oxidation states are: Students may also propose Ag2SO4 Reactants: Products: K = +1 K = +1 Cl = +5 Cl = -1 O = -2 O = 0 * Make sure your students are careful with the burner and splint. PART C: 1. Solution should turn from red to yellow. The change indicates a neutralization. 2. The acetic acid lost an H+.