Types of Chemical Reactions s1

Types of Chemical Reactions

Students should wear safety glasses and protective clothing at all times when working in the lab.

All chemical reactions fit into one of five categories. These categories are combination, decomposition, single replacement, double replacement, and combustion. Combination reactions are reactions in which the elements are combined to form a single compound. These reactions take the form A + B  AB. Decomposition reactions are the exact opposite of combination reactions, as they have a compound that falls apart into its component elements. These reactions have the general formula AB  A + B. When an element reacts with a compound to form a new element and a new compound, it is said that there has been a single replacement reaction. This is because only one single element has been replaced. These reactions can be expressed generally as A + BC  AB + C. If instead, two compounds are found in the reactants side of the equation, a double replacement reaction will occur. The double replacement reaction can be expressed as AB + CD  AD + CB. The parts of each compound are switched, leaving us with two totally different compounds as products. The final type of reaction is combustion, which occurs when your reactants are composed only of carbon, hydrogen, and oxygen atoms. Every combustion reaction ends up making only two products: carbon dioxide and water. This type of reaction can be expressed CxHxOx  CO2 + H2O

Background Information: 1. List the five types of chemical reactions: 2. Describe the differences between reactants and products. 3. Explain why iron II nitrate is not a reactant in part B.

Procedure: A. Copper Wire 1. Use the steel wool to clean a piece of copper wire until the wire is shiny. Examine the wire and note its appearance. 2. Using crucible tongs, hold the wire in the hottest part of the burner flame for 1-2 minutes. Examine the wire and note any change in its appearance caused by the heat.

B. Hydrogen Peroxide 1. Pour a small quantity of hydrogen peroxide (H2O2) in a clean, dry test tube. Note its appearance. 2. Add a small amount of catalyst (not involved in the reaction) iron (II) nitrate, to the test tube and observe. 3. Insert a glowing splint into the top of the test tube to test for oxygen gas. (The splint will burst into flame if oxygen is present) 4. Note any change in the appearance of the material in the test tube and note the appearance of any residue on the side of the test tube. C. Zinc 1. Stand a clean, dry test tube in a test tube rack. Add about 5 mL of 6 M hydrochloric acid (HCl) to the tube. Carefully drop a small piece of zinc metal into the acid in the test tube. 2. Using a test tube holder, invert a second test tube over the mouth of the test tube in which the reaction is occurring. After about 30 seconds, remove the inverted test tube and insert a burning wood splint into the tube. 3. Record all your observations about the reaction, the products, and the reactants.

D. Silver Nitrate 1. Stand two clean, dry test tubes in a test tube rack. 2. Add a few crystals of silver nitrate and 5mL of distilled water to the first test tube. Mix well, until dissolved. 3. Add a few crystals of sodium chloride and 5mL of distilled water to the first test tube. Mix well, until dissolved. 4. Record observations of your reactants. 5. Mix the test tubes. Record observations of the reaction and the products.

Write Up:

For each part of the lab (A-D):  Identify the type of reaction  Write a word equation  Write a balanced equation PART A Before Flame During Flame After Flame

Observations of Copper Appearance

PART B Initial H2O2 Reaction with End appearance appearance glowing splint

Observations of H2O2 Reaction

PART C Initial Zinc and HCl Reaction with End appearance appearance. burning splint

Observations of Zinc and HCl reaction

PART D Initial Reactant During the reaction Product appearance appearance

Observations of reaction of silver nitrate and sodium chloride Part A: Word Equation: Copper solid and oxygen gas yields copper II oxide.

Balanced Equation:

Type of Reaction:

Part B: Word Equation: Liquid dihydrogen dioxide (also called hydrogen peroxide) yields liquid water and oxygen gas.

Balanced Equation:

Type of Reaction:

Part C: Word Equation: Zinc solid and aqueous hydrogen chloride yields aqueous zinc chloride and hydrogen gas.

Balanced Equation:

Type of Reaction:

Part D: Word Equation: Aqueous silver nitrate and aqueous sodium chloride yielded silver chloride solid and aqueous sodium nitrate.

Balanced Equation:

Type of Reaction: