o Test tube In this experiment, you ll be observing the signs of chemical reactions. These include the following:

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1 Experiment: Chemical Reactions & Chemical s Objective In this experiment, students perform a variety of chemical reactions. For each reaction, student identify the signs that a reaction has occurred, write the balanced chemical equation with appropriate phases and classify the reaction. Materials o Copper (BB bullets) o Acetic acid (vinegar) o Calcium oxide (limewater) o Small beaker o Baking soda (NaHCO3) o Spoon o Muriatic acid (HCl) o Forceps o Deionized water o Ethanol o Sugar (sucrose) o Straw o Magnesium o Test tube Introduction Reading: Chemistry in our Lives Timberlake. Chapter 7.1 s for Chemical Reactions, 7.2 Types of Chemical Reactions, and 9.2 Electrolytes and Non-Electrolytes. In this experiment, you ll be observing the signs of chemical reactions. These include the following: Color Change Formation of Bubbles, indicates that one of the products is a gas. Ex. H2, O2 or H2O vapor Flame A change in temperature of the reaction mixture Formation of a precipitate. 57

2 Procedure Reaction A: Oxidation of Copper by Air (O 2 ) Add copper shots to a crucible so that it barely covers the bottom. Position the open crucible in a clay triangle supported by an O-ring clamp attached to a ring stand. Heat the bottom of the crucible with a Bunsen burner until the bottom glows red. Turn off the burner and allow the content to cool. Write on your datasheet the balanced chemical equation, the type of reaction and the driving force for the reaction. Empty all chemicals in the proper waste container after you finish. Reaction B: Combination of CaO with CO2 Pour limewater in to a 250 ml beaker. Using a straw, blow into the solution. Observe what happens to the solution as you continue to blow bubbles. Write on your datasheet the balanced chemical equation, the type of reaction and the driving force for the reaction. Empty all chemicals in the proper waste container after you finish. Reaction C: Decomposition of H2O Using alligator clips, connect the red wire to the positive terminal of a 9-V battery and the black terminal to the negative terminal. Take care not to touch the bare ends of the terminal. Connect the other ends of the alligator clips to graphite rods. Take a glass of deionized water and add about 1 gram of sodium chloride (about a spatula tip). Place both graphite rods into the water, taking care that they do not touch, and record your observations. Write on your datasheet the balanced chemical equation, the type of reaction and the driving force for the reaction. When done making your observations, return all equipment clean and dry to its original storage location. Reaction D: Combustion of Sucrose (C 12 H 22 O 11 ) Carry out this procedure under the hood. A deflagration spoon is used in this procedure as shown in the figure. Place a teaspoon (~5 grams) of sugar in the deflagration spoon and then heat over a Bunsen burner. Write on your datasheet the balanced chemical equation, the type of reaction and the driving force for the reaction. Empty all chemicals in the proper waste container, clean the deflagration spoon and return to its original location. Reaction E: Combustion of ethanol (C2H5OH) with oxygen (O2). Carry out this procedure under the hood. A deflagration spoon is used in this procedure as shown in the figure below. Add a small amount of ethanol (~0.5 ml) to a deflagration spoon. Use a Bunsen burner to burn the ethanol. Only a small amount of ethanol is necessary for safety precautions. Write on your datasheet the balanced chemical equation, the type of reaction and the driving force for the reaction. Empty all chemicals in the proper waste container when you finish and return all equipment clean back to its original location. Reaction F: Magnesium Ribbon with Muriatic Acid, HCl Add 2ml of Muriatic acid (HCl) to an empty test tube. Add a 1-cm strip magnesium ribbon to the test tube using a forceps. Write on your datasheet the balanced chemical equation, the type of reaction and the driving force for the reaction. Additional Reaction: Fill a clean test tube with 2mL of deionized water. Place the test tube in a warm bath for 5 min. Add two drops of phenolphthalein indicator to the water. Phenolphthalein is an indicator that changes color (pink) in the presence of hydroxides.* Add a 1-cm strip of magnesium to the test tube and wait 15 minutes for the reaction to take place. After 15 minutes record in your datasheet your observation. Is there the presence of hydroxide formation? Write the chemical reactions that occur in your datasheet. * In general, alkaloid metals will react with water to form metal hydroxides and hydrogen gas. 58

3 Reaction G: Baking soda with Vinegar (CH3COOH). Halfway fill an evaporating dish with vinegar. Sprinkle baking soda on to the vinegar and record your observations. Write on your datasheet the balanced chemical equation, the type of reaction and the driving force for the reaction. Empty all chemicals in the proper waste container after you finish. Hint: See Exercise 8A, if you need help writing this equation. Clean up Wash and dry all your glassware equipment. Dispose of all used chemicals in the proper waste container. Wipe down your station and place your glassware and equipment back in its proper place. Unless your equipment is back in the locker drawer, you are not allowed to remove your safety goggles. Wash your hands thoroughly with soap and water before leaving your work area. 59

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5 Experiment 9: Data Sheets Last Name First / pts aaaa. Lab Partner(s): Day pppp. Reaction A: Oxidation of Copper by Air (O 2 ) to produce copper (II) oxide Balanced Chemical Reaction B: Combination of CaO with CO 2 to produce calcium carbonate Balanced Chemical 61

6 Reaction C: Decomposition of H2O into hydrogen and oxygen gas Balanced Chemical ** ** NaCl is used for carrying of e- and is not part of the chemical equation. Reaction D: Combustion of Sucrose (C 12 H 22 O 11 ) Balanced Chemical 62

7 Reaction E: Combustion of Ethanol (C2H5OH) with oxygen (O2). Balanced Chemical Reaction F: Magnesium Ribbon with Muriatic Acid, HCl to produce hydrogen and magnesium chloride Balanced Molecular Chemical Total Ionic Net Ionic 63

8 Reaction G: Baking soda with Vinegar (CH3COOH). Balanced Molecular Chemical Total Ionic Net Ionic 64

9 Postlab Questions 1. Check all the reactions in this lab, which produced a precipitate. Oxidation of Copper Decomposition of H2O Reaction Mg ribbon with HCl Baking soda and Vinegar Combination of CaO and CO2 Decomposition of Sugar Ethanol with Oxygen 2. Check all reactions in this lab that showed evidence of the release or absorption of heat. (Do not confuse the release of heat with providing an external addition of heat, ie. Heating with a Bunsen burner) Oxidation of Copper Decomposition of H2O Reaction Mg ribbon with HCl Baking soda and Vinegar Combination of CaO and CO2 Decomposition of Sugar Ethanol with Oxygen 3. Check all the reactions in this lab, which were accompanied by the evolution of gas. Oxidation of Copper Decomposition of H2O Reaction Mg ribbon with HCl Baking soda and Vinegar Combination of CaO and CO2 Decomposition of Sugar Ethanol with Oxygen 65

10 4. What is the color of the sugar before and after combustion? What is the identity of the gases you observed? 5. What is the gas formed in the reaction between baking soda and vinegar? 66