Classifying Chemical Reactions Lab PDF

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Classifying Chemical Reactions Analyzing and Predicting Products Name __________________________________ Background: In a chemical equation, the reactants are written on the left side of the equation, the products on the right side of the equation. An arrow represents the direction of the reaction and is read as “yields” or “produces.” Chemical reactions can be classified by considering the number of reactants and products in the reaction, the physical or chemical nature of the reactants and products, and the how the atoms are rearranged during the reaction. The table below summarizes some of the most common reaction types. Notice that none of the reactions are balanced; you balance these reactions as part of the pre-lab activities.

Synthesis

Types of Chemical Reactions Two reactants combine to form a single product. The reactants may be elements or compounds. Also called a synthesis reaction.

Combustion emenDoublecemenSingle Decompositi on

___ Na (s) + ___ Cl2 (g)  ___ NaCl (s) One complex reactant breaks down to give two or more simpler products. ___ H2O2 (l)  ___ H2O (l) + ___ O2 (g) An element reacts with a compound and replaces one the elements in the compound. Elements with positive oxidation numbers must replace atoms with a positive oxidation. The same is true for elements with negative oxidation numbers. Two ionic compounds exchange ions to form new compounds. ___ CuCl2 (aq) + ___ Na3PO4 (aq)  ___ Cu3(PO4)2 (s) + ___ NaCl (aq) H SO ( burns ) OHpresence ( )  of oxygen, H O (l) producing N SO ) A compound inNthe heat( and light. The combustion of organic compounds (compounds made of carbon) produces carbon dioxide and water. ___ C8H18 (l) + ___ O2 (g)  ___ CO2 (g) + ___ H2O (l)

Pre-Lab Questions and Activities: 1. Balance the equations in the previous table. 1

2. Summarize the following chemical reactions by writing a balanced chemical equation for each. Indicate whether each is a combination, decomposition, single replacement, double replacement, or combustion reaction. a. “When solid sodium bicarbonate is heated in a test tube, carbon dioxide is released in the surrounding air. Water condenses at the mouth of the test tube and a white solid residue, sodium carbonate, remains at the bottom of the test tube.” Balanced Chemical Equation

Type of Reaction

b. “Hydrogen gas is placed in a balloon with oxygen gas and a flame is placed against the surface of the balloon. When the balloon pops a spectacular explosion follows and steam is produced.” Balanced Chemical Equation

Type of Reaction

c. “Pellets of solid sodium hydroxide are dropped in to a golden brown solution of iron(III) chloride and a dark brown precipitate forms. The precipitate is iron(III) hydroxide. The other product, table salt is still dissolved in the solution.” Balanced Chemical Equation

Type of Reaction

d. “Older air bags in cars inflate the air bags when an electrical spark, triggered by sensors located at a variety of points in the car, caused solid sodium azide (NaN3) to rapidly turn in solid sodium and nitrogen gas.” Balanced Chemical Equation

Type of Reaction

e. “When chlorine gas is bubbled through a solution of calcium bromide, the solution turns a dark brown color indicating the presence of dissolved bromine. Calcium chloride is also produced.” Balanced Chemical Equation

Type of Reaction 2

3. Make an entry for this lab in the Table of Contents of your lab notebook. At the top of the next page open page, write the title of the activity, reread the introduction and write a purpose for the lab. 4. Read the procedure below and summarize the procedure for reaction A in your lab notebook. Although you may summarize each step, you need to have the same number of steps. 5. After the summarized reaction procedure, you will need to draw a data table for that reaction. The table should be almost as wide as the page and at least fifteen rows high. Use the table below as an example for what to include. Evidence of Chemical Change Appearance of Reactant & Properties of Products Balanced Chemical Equation 6. Repeat steps 4 & 5 for the remaining reactions. Materials:  Ammonium Carbonate (______)  Phenolphthalein indicator  Calcium Carbonate (______)  Zinc  Copper (II) chloride (______)  Bunsen Burner  Cobalt (II) nitrate (______)  Spatula  1M Sodium hydroxide (______)  Test tubes, 6  0.5M Sodium phosphate (____)  Test Tube Holder  Ethanol, C2H5OH  Test Tube Rack  Hydrochloric acid, HCl  Wood Splints  Magnesium Safety Precautions: Ethanol and phenolphthalein are both flammable liquids and should not be stored or used around open flames. Hydrochloric acid and sodium hydroxide are corrosive and will cause chemicals burns with prolonged contact. Notify the teacher of any spills and wash exposed skin immediately if you come in contact. Copper(II) chloride and cobalt(II) nitrate are both mildly toxic by ingestion and contact should be avoided. At the end of the lab, be sure to wipe down your lab station and wash your hands. You must wear chemical splash goggles at all times. You may remove your goggles after you have 3

returned all chemicals, wiped down the lab counter, and washed your hands with soap and water. Procedure: Reaction A 1. Add approximately 2mL of 1 M hydrochloric acid (HCl) to a watch glass 1. 2. Obtain a 2-3cm strip of Mg and coil it into a loose ball. Drop the magnesium into hydrochloric acid. 3. While the reaction is taking place, light a match and hold flame directly above the bubbles. 4. The products of the reaction are hydrogen gas and magnesium chloride, which is soluble in water. Write out and balance the equation in your data table and identify the type of reaction. Reaction B 1. Using a clean dry test tube, place a jelly bean sized pile of ammonium carbonate into a test tube. Note the odor of the ammonium carbonate. DO NOT sniff the test tube; use your hand to waft the odor to your nose. 2. Smelling chemicals directly may expose you to dangerously high concentrations. 3. Use a test tube clamp and gently heat the test tube in a Bunsen Burner for about 30s. 4. Remove the test tube and note the odor. DO NOT sniff the test tube; use your hand to waft to odor to your nose. 5. To test for the formation of a gas, light a wood splint and insert the burning splint halfway down the test tube. 6. Record your observations in the data table. 7. The heat from the Bunsen burner causes the ammonium carbonate to break down into ammonia gas (NH3), which was the strong odor you smelled, and carbon dioxide. Write out and balance the equation in your data table and identify the type of reaction. Reaction C 1. Place a small amount (about the size of a jelly bean) of calcium carbonate in a clean and dry test tube. 2. Using the appropriate pipette, add about 1mL of hydrochloric acid to the test tube. Feel the sides of the test tube and observe the reaction for 30 seconds. 3. While the reaction is still taking place, light a wood splint and place the splint in the test tube. Do not allow the splint to touch the acidic solution. 4. Record your observations in the data table. 4

5. The reaction resulted in the production of soluble calcium chloride, water, and carbon dioxide. Reaction D 1. Add about 1mL of cobalt (II) nitrate solution to a clean test tube. 2. Add several drops of 1M sodium hydroxide (______) to the cobalt(II) nitrate. 3. Allow the test tube to sit for a few minutes undisturbed. What do we call a solid that is formed when two liquids are mixed? 4. Record your observations in the data table. 5. This reaction produces insoluble cobalt(II) hydroxide and soluble sodium nitrate. Reaction E 1. Add about 2mL of copper(II) chloride solution into a clean test tube. 2. Place a small piece of zinc in the test tube and observe the reaction. 3. Record your observations in the data table. 4. When the solid zinc reacts with the dissolved copper(II) chloride solution, soluble zinc chloride and solid copper are formed.

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Reaction F 1. Add exactly 20 drops of sodium hydroxide solution into a small test tube. 2. Add 2 drops of the phenolphthalein solution and swirl the test tube to mix. (Phenolphthalein is called and acid base indicator.) 3. Add a one drop of the 1M hydrochloric acid (HCl) and swirl. Count the number drops required for a permanent color change to be observed. 4. Record your observations in the data table. 5. When this strong acid and base are mixed, the result is salt and water. Reaction G 1. Half fill a test tube with cold water. Clamp a test tube holder around the test tube and set it aside. 2. Clear off a large area of the lab counter. Put about 25 drops of ethanol (C2H5OH) directly on the lab counter in the center of cleared off area. Cap the ethanol and remove it from the cleared off area. 3. Lower a lit match toward the pool of alcohol until it ignites. 4. Using the test tube holder, hold the test tube with cold water over the flame. Observe the outside of the test tube for evidence of product formation. Record your observations in the data table. 5. Ethanol reacts with oxygen to produce carbon dioxide and water. Post Lab Questions: 1. Classifying chemical reactions helps chemists predict the possible products that will form when two or more substances are mixed. Complete and balance the following equations by predicting the products of each chemical reaction. Write the final equation in your lab notebook. Be sure to balance the equations. a. Double replacement: ____ NaOH (aq) + ____ CuSO4 (aq)  b. Combination: ____ Al (s) + ____ O2 (g)  c. Combustion: ____ C6H12O6 (s) + ____ O2 (g)  d. Decomposition: ____ CaCO3 (s)  e. Single Replacement: ____ Fe (s) + ____ Pb(NO3)2 (aq)  2. Describe the five chemical equations in post lab question 1 using words rather than symbols and formulas. Record your descriptions in your lab notebook. For example the chemical reaction below can be described as follows. 3 CuCl2 (aq) + 2 Na3PO4 (aq)  Cu3(PO4)2 (s) + 6 NaCl (aq) “A double replacement reaction takes place when aqueous copper(II) chloride is mixed with aqueous sodium phosphate; the products include a solid precipitate of copper(II) phosphate and aqueous sodium chloride.” 6...