TYPES OF CHEMICAL REACTIONS A Laboratory Investigation Purpose: Observe the five major types of reactions. Record observations for these reactions. Complete balanced equations for these reactions. Introduction: There are many kinds of chemical reactions and several ways to classify them. The five general types of reactions that you will study in this lab activity are: synthesis, decomposition, combustion (or burning), single replacement, and double replacement. Not all reactions can be put into one of these categories. Many, however, can. Recognizing and using types of reactions can make determining the reactants and products much easier. In synthesis reactions, two or more substances combine to form a more complex compound. In decomposition reactions (the opposite of synthesis), a complex compound breaks down to form two or more simpler substances. In single replacement reactions, one element is displaced from its compound by a more active element. In double replacement reactions, ions in solution combine to form a new product such as a solid precipitate, an insoluble gas, or as a new molecular species (usually water). During any chemical reaction, the Law of Conservation of Matter must be satisfied. Recording of Results: For each of the following reactions, you will complete the student data table including the REACTANTS, OBSERVATIONS BEFORE REACTION and OBSERVATIONS DURING/AFTER REACTION. As well as recording the PRODUCT, BALANCED EQUATION and TYPE OF REACTION columns. YOU NEED TO WEAR GOGGLES AT ALL TIMES WHILE PERFORMING THIS LAB. Procedure: After you have finished Reaction 1, start Reactions 8 & 9 because they will need to sit for 20 and 30 min. respectively. Section I: Synthesis reactions A + B AB Synthesis reactions occur when two or more substances come together to form a single new substance. Reaction 1. Magnesium Obtain a 10 cm strip of Magnesium ribbon. Holding one end with forceps, ignite the other end in a Bunsen burner flame. After ignition, hold the burning magnesium over a ceramic fiber square until the reaction is complete. Do not look directly at the burning magnesium!
Describe and identify the product. (hint: magnesium reacts with oxygen to produce magnesium oxide.) Reaction 2: Steel wool (containing Fe) and oxygen Remove a small piece of steel wool from the wool pad on the lab bench. Pull it apart so that the wool strands are loosely separated. Use crucible tongs to hold the steel wool in the Bunsen burner flame. Reaction 3: Carbon dioxide and water Pour 50 ml of water into a plastic cup. Place the cup on white paper. Add 3 drops of bromothymol blue indicator to the flask. Use a straw to blow bubbles into the water indicator mixture. Observe and record the color of the mixture. Your reactants are water and carbon dioxide. o What acidic product can you predict for this combination reaction? Write a chemical equation for this reaction. (hint: your breath is carbon dioxide) Section II: Decomposition reactions AB A + B Decomposition reactions result as one substance breaks down to two or more simpler substances. Reaction 4: Decomposition of sodium hydrogen carbonate (NaHCO 3 ) Place a small amount of sodium hydrogen carbonate (baking soda) into a test tube. Use a test tube holder to grip the test tube and place the test tube into the Bunsen burner flame. Point the mouth of the test tube away from people. Observe the mouth of the test tube for moisture. (There are three products of this reaction: carbon dioxide, water and sodium carbonate.) Record your observations. Write a chemical equation for this reaction. Reaction 5. Decomposition of Copper Sulfate Place a small amount of copper (II) sulfate crystals into a small test tube. Hold the test tube with a test tube clamp and situate the tube at an angle with the mouth slightly downward. Heat the hydrate over a Bunsen burner until the chemical reaction is complete (the reaction should be obvious). [NOTE: a hydrate is a compound that contains water. The formula of a hydrate is written a little differently than formulas for other compounds. The formula for the hydrate of copper (II) sulfate is written CuSO 4 5H 2 O. This means there are five water molecules bound to one CuSO 4 molecule. (The correct name for this compound is copper (II) sulfate pentahydrate). When copper (II) sulfate pentahydrate is heated, anhydrous copper (II) sulfate and water vapor are produced. (Anhydrous means no water ) ] Reaction 6. Decomposition of sucrose Fold up the sides of an aluminum foil square to make a small tray. Use a wooden stick to put a pea-sized pile of sugar onto the tray. Use forceps to hold the aluminum tray. Heat the sugar slowly by moving the tray gently back and forth over a flame. Make observations, while the sugar is heating. When you think there is no longer a chemical reaction occurring, turn off the flame. Allow the tray to cool for a few seconds and set it down on your desk. Record your observations of the material left in the tray.
Section III: Single replacement reactions A + BC AC + B In this reaction, one substance will replace another substance in the compound. Reaction 7. Zinc and Hydrochloric acid Place a small piece of mossy zinc into a test tube. Add enough dilute (3.0 M) hydrochloric acid to cover the zinc. After 1 minute, place a flaming splint into the mouth of the test tube. Describe and record the results in the data table. For disposal, fill the test tube with water and dump the solution in the waste bucket. Discard the remaining solid in the garbage. (hint: Zinc reacts with aqueous hydrochloric acid to produce aqueous zinc (II) chloride and hydrogen gas.) Reaction 8. Magnesium and copper sulfate Place a small strip of magnesium ribbon in a test tube. Add enough copper (II) sulfate solution to cover the magnesium. Allow to remain for at least 20 minutes. Describe and record the results in the data table. (hint: Aqueous Copper (II) sulfate reacts with magnesium to produce aqueous magnesium sulfate and copper.) Discard the solid in the waste and the solution in the liquid waste bucket. Reaction 9. Silver nitrate and copper Place 5 ml of silver nitrate solution into a clean test tube. CAUTION: Do not allow the silver nitrate solution to come in contact with your skin or clothes. Clean up any spills immediately, discard paper towels, and wash hands with soap. Clean a copper strip and place into the test tube containing the silver nitrate solution. Allow this to remain undisturbed for at least 30 minutes. Note the substance which forms on the copper strip and any changes in the color of the solution. Describe and record the results in the data table. Carefully, discard the solution down the drain and place the solid in the designated waste container in the fume hood! DO NOT DISCARD THIS PRODUCT! Section IV: Double replacement reactions AB + CD AD + CB In double replacement reactions, the substances are ionized and dissolved in water. The ions are free to move around and find another partner. If the partnership results in a compound which is insoluble in water, a precipitate (a solid) will form. If a gas is formed, you will see bubbles. Reaction 10. Potassium iodide and lead nitrate Place a few drops of potassium iodide solution in a small test tube. Record your observations. Add a few drops of lead (II) nitrate. Record your observations. Dump the liquid content in the trash do not flush down the sink.
Reaction 11. Aluminum chloride and ammonium hydroxide Fill a small test tube about ½ full of aluminum chloride solution. Add approx. 1 ml of ammonium hydroxide solution. Describe and record the results in the data table. Discard the products in the waste container. Reaction 12. Copper sulfate and sodium carbonate Fill a small test tube about ½ full of copper sulfate solution. CAUTION: Copper sulfate is poisonous and can stain your skin and clothes. Do not touch it or get it in your mouth. Put an equal amount of sodium carbonate solution in another test tube. Record the appearance of both liquids on the data table. Combine the two solutions into one test tube and record your observations. Note- the reaction occurs quickly. Dispose of the solution in the liquid waste container. Reaction 13. Silver nitrate and sodium chloride Place about 10 drops of silver nitrate (AgNO 3 ) in a test tube. Add about 10 drops of sodium chloride (NaCl) solution into the test tube. Write an equation for this reaction. (hint: Aqueous silver nitrate reacts with aqueous sodium chloride to produce solid silver chloride and aqueous sodium nitrate.) Reaction 14: baking soda and hydrochloric acid Place a small amount of baking soda (sodium hydrogen carbonate - NaHCO 3 ) into a test tube. Drop some dilute (approx. 0.1 M) HCl into the test tube with the baking soda. Put a flaming splint near the opening of the test tube. Notice that CO 2 is produced. How do you know? Write the equation for this reaction. Other products include water and an ionic salt. Write an equation for this reaction. Section V: Combustion of hydrocarbons Hydrocarbon + O 2 CO 2 + H 2 O When a compound composed of carbon and hydrogen completely burns in the presence of oxygen, carbon dioxide and water are produced. Reaction 15: The combustion of methane The gas you are burning in the Bunsen burner is methane gas, CH 4. Light the burner and record a description of the flame for your observation. Write a complete balanced equation for this reaction. Reaction 16: The combustion of ethanol Place 15 drops of ethanol (C 2 H 5 OH) onto a watch glass. Light a wooden splint and place it near the ethanol. Record your observations. Write a complete balanced equation for this reaction.
Section I: Synthesis reactions A + B AB Examples of SYNTHESIS Cu(s) + O 2 (g) CuO(s) Mg(s) + O 2 (g) MgO(s) Section II: Decomposition reactions AB A + B Example of DECOMPOSITION CuCO 3 (s) CuO(s) + CO 2 (g) Section III: Single replacement reactions A + BC AC + B Examples of SINGLE REPLACEMENT Zn(s) + HCl(aq) ZnCl 2 (aq) + H 2 (g) Zn(s) + CuSO 4 (aq) ZnSO 4 (aq) + Cu(s) Section IV: Double replacement reactions AB + CD AD + CB Example of DOUBLE REPLACEMENT Pb(NO 3 ) 2 (aq) + KI(aq) KNO 3 (aq) + PbI 2 (s) Section V: Combustion of hydrocarbons Hydrocarbon + O 2 CO 2 + H 2 O