Experiment 5: Introduction to Chemical Reactions

One of the most fascinating features of a chemistry class is the opportunity to carry out chemical reactions. Many of these produce unexpected and exciting results. This experiment will investigate several characteristic reactions.Chemists classify most reactions into five major types, based on what reacts and what is produced: Combination: Two elements and/or compounds combine to form a new compound Element or Compound + Element or Compound à Compound Decomposition: A compound is broken down into two simpler substances Compound à Element or Compound + Element or Compound Single Replacement: An element reacts with a compound Element + Compound à Different Element + Different Compound Double Replacement: Two compounds react together, producing two new compounds Compound A+ Compound Bà Compound C + Compound D Combustion: A hydrocarbon (something containing carbon and hydrogen) reacts with oxygen gas, producing carbon dioxide and water Hydrocarbon + Oxygen à Carbon Dioxide + WaterIt will be your job today to describe several different reactions, and then indicate which category best describes them. Enjoy, but be safe!ProcedureCarry out each reaction in a clean test tube unless otherwise indicated. Then, record observations on your report sheet. Be as specific as possible, indicating the state(solid, liquid, gas), color, and other interesting observations of the chemical products. Reaction #1: This reaction must be carried out in the fume hood. Place a few pieces (3 to 4) of copper metal into a test tube. Slowly add a few drops of 6 M nitric acid (HNO3) to this tube. You should see a quick and vigorous chemical reaction. Record your observations. Allow the reaction to go to completion and any gases to dissipate before removing your test tube from the fume hood. Any liquid may go down the drain with running water, but solids should go in the trash.Reaction #2: Place a few pieces of copper metal in a different test tube. Add about 2 mL (40 drops should be fine) of 0.1 M silver nitrate solution, (AgNO3) to the tube. Do not get this on your skin, or it may cause dark spots to appear! Set the tube aside for several minutes. Record your observations when you are done. Pour any liquids in the container marked “Silver waste”; solids should go in the trash.Reaction #3: Read the directions for this reaction completely before beginning! This reaction must be carried out by a group of two students. Add a piece of zinc (sometimes called “mossy zinc”) to 5 mL of 6 M hydrochloric acid (HCl) in a test tube. Place your thumb over the mouth of the test tube, but do not shake it. A partner should be ready to light a match and hand it to you. You will soon (about 40 seconds into the reaction) feel pressure building up in the tube. Move the test tube near the flaming match and quickly release your thumb so that you do not burn it. Do not stick the match into the test tube, and do not point the test tube at anyone (including yourself)! Any liquid wastes may go down the drain with running water, solids into the trash.Reactions 4 & 5: Pour 5 mL of distilled water into your evaporating dish. Then, add one drop of phenolphthalein to it. Ignite a small piece of magnesium by holding it in a Bunsen burner flame with tongs. Do not look directly at the reaction. After the reaction has completed, observe the product you have formed, then drop it into the evaporating dish, where yet another reaction will occur. A change in the color of the solution indicates that you have made a basic solution (one which contains hydroxide ions). A base can be thought of as the opposite of an acid. The products may go down the drain.Reaction 6: Place 20 drops of 0.1 M copper (II) sulfate solution (CuSO4) into a test tube. To this, add exactly one drop of 6 M ammonia solution (NH3), and stir with a stirring rod. Record your observations, but do not dispose of the contents of this test tube.Reaction 7: Add 10 more drops of 6 M NH3 to the test tube from Reaction 6, and stir with a glass stirring rod. Record your observations, then pour the liquids down the drain with running water.Reaction 8: Pour 2 mL (40 drops) of 0.1 M lead (II) nitrate (Pb(NO3)2) in one test tube, and 2 mL of 0.1 M potassium iodide (KI) in another. Record what each of these solutions looks like, then combine the contents of each. Pour the waste in the “lead waste”Reaction 9: Place 5 drops of 0.1 M iron (III) chloride (FeCl3) in a clean test tube. Using your spatula, add one small crystal of ammonium thiocyanate (NH4SCN) to the solution, and stir with a clean stir bar. Dispose of the products in the container labeled “Reaction 9 Waste”.

Report Sheet Name:______

Introduction to Chemical Reactions

Record your observations below, and indicate the type of reaction which best describes each. You are not required to provide the reactions type for reactions six, seven, and nine; the equations for these are somewhat complex.
Reaction One:
Word equation: copper + nitric acid à copper (II) nitrate + nitrogen dioxide
Type of reaction:______
Observations:

Reaction Two:
Word equation: copper + silver nitrate à silver + copper (II) nitrate
Type of reaction:______
Observations:


Reaction Three:
Word equation: zinc + hydrochloric acid à hydrogen + zinc chloride
Type of reaction:______
Observations:

Reaction Four:
Word equation: magnesium + oxygen à magnesium oxide
Type of reaction:______
Observations:

Reaction Five:
Word equation: magnesium oxide + water à magnesium hydroxide
Type of reaction:______
Observations:


Reaction Six:
Observations:

Reaction Seven:
Observations:

Reaction Eight:
Word equation: lead (II) nitrate + potassium iodide à lead (II) iodide + potassium nitrate
Type of reaction:______
Observations:
Reaction Nine:
Observations:


Preparation for this experiment:
Pieces of copper foil (or thin strips) [1-2 small containers]
Pieces of “mossy” zinc [1-2 small containers]
Pieces of magnesium ribbon [1-2 small containers]
Ammonium thiocyanate [1-2 small containers]
Phenolphthalein solution in dropper bottles
2-3 dropper bottles (50-100 mL) containing each of the following aqueous solutions:
6 M HNO3
0.1 M AgNO3
6 M HCl
0.1 M CuSO4
6 M NH4OH (label as 6 M NH3)
0.1 M Pb(NO3)2
0.1 M KI
0.1 M FeCl3
Waste containers: “Lead Waste”, “Silver Waste”, “Reaction 9 Waste”

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