Reactions Crystal Gambino & Renee Y. Becker Manatee Community College

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1 Reactions Crystal Gambino & Renee Y. Becker Manatee Community College Purpose: To observe chemical reactions and write chemical equations based on laboratory observations. Introduction: The heart of chemistry is found in chemical reactions. In this experiment you will investigate 6 different reactions. Chemical reactions can be classified in many different ways. One classification system involves looking at the chemical equation for the reaction. There are seven possible reaction types: combination, decomposition, double displacement, single displacement, acid-base neutralization, redox, and precipitation. A chemical reaction can be classified by comparing the chemical equation to the generic reaction equation for each reaction type. Combination: A + B C Decomposition: Example: 2 Cu (s) + O 2(g) 2 CuO (s) C A + B Example: 2 HgO (s) 2 Hg (l) + O 2(g) Double displacement: AB + CD AD + CB Example: AgNO 3(aq) + KCl (aq) AgCl (s) + KNO 3(aq) This is also a precipitation reaction: Reactants are aqueous solutions and one of the products is a solid. Precipitation reaction tells us more about the reaction therefore it is a better answer for this type of reaction. Example: HBr (aq) + NaOH (aq) H 2 O (l) + NaBr (aq) This is also an acid-base neutralization reaction: The reactants are an acid and a base and the products will be a salt and water. Acidbase neutralization reaction tells us more about the reaction therefore it is a better answer for this type of reaction. 1

2 Single displacement: A + BC AC + B Example: Cu (s) + 2AgNO 3(aq) Cu(NO 3 ) 2(aq) + 2Ag (s) A + BC BA + C Example: 2Na (s) + 2H 2 O (l) 2NaOH (aq) + H 2(g) Both of these reactions are also reduction-oxidation (redox) reactions. One of the reactants was reduced (gained electrons) and one was oxidized (lost electrons). Redox reaction tells us more about the reaction therefore it is a better answer for this type of reaction. Materials: Apparatus: Chemicals: 6 clean test tubes Test tube rack Test tube holder Bunsen burner Crucible tongs Magnesium ribbon 0.1 M Hydrochloric acid solution 0.2 M Calcium nitrate solution 0.2 M Sodium carbonate solution Copper (II) sulfate pentahydrate solid 0.1 M Sodium hydroxide solution Phenolphthalein indicator solution Steel wool (Iron) solid 0.1 M Copper (II) sulfate solution Ammonium carbonate solid 2

3 Procedure: Reaction #1 1. Place a 1 cm piece of magnesium in a clean test tube and record the appearance of the magnesium. 2. Measure 1 ml of 0.1 M hydrochloric acid solution, record its appearance and add it to the test tube with the magnesium. 3. Observe and record your results. 4. Discard the reaction mixture into the magnesium solution waste container. Reaction #2 1. Measure out 1 ml of 0.2 M calcium nitrate solution and record its appearance then place it in a clean dry test tube. 2. Measure out 1 ml of 0.2 M sodium carbonate solution and record its appearance then place it in the test tube with the calcium nitrate solution. 3. Observe and record your results. 4. Pour the reaction mixture down the drain. Reaction #3 1. Place a pea size amount of copper (II) sulfate pentahydrate in a clean test tube. 2. Record the appearance of the copper (II) sulfate pentahydrate. 3. While holding the test tube with test tube holders strongly heat the contents over a Bunsen burner. (Make sure the test is at a 45 o angle away from you or any other person) 4. Once you see a color change, stop the heating and record you results. 5. Dispose of the waste in the iron/copper waste container. Reaction #4 1. Measure out 1 ml of 0.1M hydrochloric acid solution and place it in a clean test tube. 2. Add 1 drop of phenolphthalein indicator solution to the test tube and record the appearance of the acid and the phenolphthalein solution. 3. Obtain a dropper bottle of 0.1M sodium hydroxide solution and record it appearance. 4. Add 0.1 M sodium hydroxide drop wise to the hydrochloric acid in the test tube until you see a color change. 5. Observe how many drops it takes and the color it changes to, and then record your results. 6. Pour the reaction mixture down the drain. 3

4 Reaction #5 1. Place a pea size piece of steel wool (iron) in a clean test tube and record the appearance of the iron. 2. Measure 1 ml of 0.1 M copper (II) sulfate solution, record its appearance, and add it to the test tube with the iron. 3. Wait 5 minutes, observe and record your results. 4. Discard the reaction mixture into the iron/copper waste container. Reaction #6 1. Place a pea size amount of ammonium carbonate in a clean test tube. 2. Record the appearance of the ammonium carbonate. 3. While holding the test tube with test tube holders strongly heat the contents over a Bunsen burner. (Make sure the test is at a 45 o angle away from you or any other person) 4. Heat for around 30 sec. 5. Carefully fan the vapors toward your nose and record the odor. 6. If you cannot detect any odor repeat step Put the solid into the magnesium solution waste container. 4

5 Pre-lab Questions: 1. Give the complete ionic equation for the following reaction AgNO 3(aq) + KCl (aq) AgCl (s) + KNO 3(aq) 2. Give the net ionic equation for the following reaction H 2 SO 4(aq) + KOH (aq) H 2 O (l) + K 2 SO 4(aq) 3. Give four different physical observation that would indicate a chemical reaction has occurred. a. b. c. d. 4. What are the spectator ions found in the reaction in question #2? 5

6 Data Table: Reaction #1 (a). Appearance of magnesium: (b). Appearance of hydrochloric acid solution: (e). Net ionic reaction: Reaction #2 (a). Appearance of calcium nitrate solution: (b). Appearance of sodium carbonate solution: (e). Net ionic reaction: 6

7 Reaction #3 (a). Appearance of copper (II) sulfate before heating: (b). Appearance of copper (II) sulfate after heating: (e). Reaction type: Reaction #4 (a). Appearance of hydrochloric acid solution with phenolphthalein: (b). Appearance of sodium hydroxide solution: (c). Number of drops of sodium hydroxide needed for color change and final solution color: (d). Balanced chemical equation (not including phenolphthalein): (e). Net ionic reaction: 7

8 Reaction #5 (a). Appearance of steel wool (iron): (b). Appearance of copper (II) sulfate solution: (e). Net ionic reaction: Reaction #6 (a). Appearance of ammonium carbonate: (b). Odor of vapor: 8