Chemistry: Chapter 8

Chemistry: Chapter 8

Types of chemical reactions

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Introduction

In this experiment, you will learn to differentiate among five general types of chemical reactions. From your lab observations you will attempt to identify the products of each reaction and to determine the type of reaction that has taken place.

The types of reaction you will consider are the following: combination reactions, decomposition reactions, single-replacement reactions, double-replacement reactions, and combustion reactions. The majority of common chemical reactions can be classified as belonging to one of these categories.

Objectives

1. To observe chemical reactions in order to determine the reaction type.

2. To write word equations and balanced chemical equations for each reaction.

3. To identify reactant and product characteristics of each reactant type

Safety

1. Wear safety goggles and apron.

2. Hydrochloric acid is corrosive and can cause severe injury. If you spill acid on yourself, immediately flush the affected area with water for 2-3 minutes and notify the teacher. If acid should get into your eyes, begin flushing your eyes with water immediately and continue doing so for at least 20 minutes. If there is an eye wash apparatus with continuous running water in the laboratory, use it.

If acid is spilled on the laboratory bench or on the floor, neutralize the spill with solid sodium bicarbonate, NaHCO3, before wiping it up with sponges or paper towels. The acid will be neutralized when bubbles of gas no longer form after addition of sodium bicarbonate. If you need to dispose of a small quantity of acid, neutralize the sample with sodium bicarbonate before pouring it down the drain.

3. Copper(II) sulfate is an irritant. Avoid skin contact with this chemical. Wash your hands thoroughly after use.

4. Lead and copper compounds are poisonous, bio-accumulative and water pollution hazards. However, the small quantities used in this experiment will not contribute significantly to environmental pollution.

Use as little of these compounds as practical and rinse small surplus amounts down the drain. Wash your hands thoroughly after use of these compounds.

Procedure

Glowing splint test

Wood splint is ignited and then blown out so that a red, glowing cinders remains. The glowing splint, when placed in an oxygen-rich environment will glow brighter and burst into flames.

Burning splint test

Wood splint is ignited and left burning and placed over mouth of test tube. If hydrogen gas is present it burns quickly with a sharp pop or “bark”

A. Heating iron metal in air

1. Place a large ball of steel wool in the crucible.

2. Heat the crucible red hot for 5 minutes

3. After crucible cools observe contents and record your observations and reaction type in the data table.

B. Action of catalyst on hydrogen peroxide

1. Use a utility clamp to secure the tube to a ring stand. Caution: Make sure that the mouth of the tube is pointed away from you and away from everyone else.

2. Add 5 mL of the 6% hydrogen peroxide solution to a medium test tube.

3. Add a very tiny amount of manganese dioxide to serve as a catalyst

4. After you observe a gas forming for 1 minute, test for its identity with the glowing splint test (see above). Do not put the splint into the solution. Record your observations and reaction type in the data table.

C. Reaction between iron metal and copper (II) sulfate solution

1. Fill a small test tube halfway with copper(lI) sulfate solution.

2. Add a small amount of iron filings to the solution.

3. Heat very gently just until the solution boils.

4. Observe the reaction after 5 minutes. Record your observations and reaction type in the data table.

D. Reaction between magnesium metal and hydrochloric acid

1. Fill one medium-size test tube halfway with 6M hydrochloric acid. Caution: Hydrochloric acid is corrosive.

2. Place the test tube in a test tube rack. Put several magnesium pieces into the acid solution. After you observe a gas forming for 1 minute, test for its identity with the burning splint test (see above). Do not put the splint into the solution. Record your observations and reaction type in the data table.

E. Reaction between lead(II) nitrate and potassium iodide solutions.

1. Put 10 drops of lead(II) nitrate solution in a small test tube.

2. Add 5 to 10 drops of potassium iodide solution.

3. Record your observations and reaction type in the data table.

Types of Chemical Reactions Questions Name ______Pd ______

Fill out the chart below

Write a word equation and a balanced chemical equation for each of the 5 reactions you observed.

Answer the following questions on your own paper

Part A

1. Are the reactants elements or compounds?

2. Is the product an element or compound?

3. Give the formulas of both forms of iron oxide.

Part B

4. In the reaction of hydrogen peroxide manganese dioxide is a catalyst.

What is a catalyst?

5. What gas were you testing for with the glowing splint?

6. What is the other product in the reaction?

It's not hydrogen gas or you would have had an explosion with the glowing splint.

Part C

7. What evidence did you have for a chemical reaction?

8. What was the brown precipitate?

Part D

9. What gas were you testing for with the burning splint?

10. Where did the hydrogen gas come from?

11. What other product was formed?

Part E

12. What evidence did you have that a chemical reaction occurred?

13. What was the name and formula of the precipitate?