Experiment Six

Classification of Chemical Reactions

Balancing Chemical Reactions

 

 

Procedural Tips

FAQ

Introduction/Goals

Background

Pre-lab

Additional Problems

Supplies and Chemicals

Safety Precautions

Waste Disposal Instructions

Chem 106 Lab Homepage


You will make observations concerning physical and chemical changes in reactions. In addition, you will classify chemical reactions as to type.
Text Box: You will make observations concerning physical and chemical changes in reactions. In addition, you will classify chemical reactions as to type.
 

 

 

 

Print a copy of the Grading Sheet for this lab.

Procedural Tips:

Evidence of Chemical Reactions

Using the Bunsen Burner

FAQ:

Why do I have to wear safety goggles?

Introduction/Goals:

In this experiment, we will observe reactions that compounds undergo and determine whether a chemical or physical change has occurred. Observations that indicate a chemical reaction has occurred include such changes as a change in color, the formation of a solid or the formation of a gas. If a chemical reaction has occurred a balanced reaction will be written for the reaction and the reaction will be identified as a combination, decomposition, replacement, or combustion reaction.

Goals:
bullet

Classify a change as a chemical or physical change.

bullet

Write balanced equations for chemical reactions.

bullet

Classify chemical reactions as combination, decomposition, replacement, or combustion reactions.

Background:

Chemical vs. Physical Change:

When a substance undergoes a chemical change, a new substance is produced. The new substance will have a different composition and also different properties than the original substance. These changes take place as the result of a chemical reaction.

In a physical change, the substance is not altered. Only its appearance is changed. No new substance has been formed. For example, when we melt ice to liquid water a physical change occurs. We still have the same substance - H2O- but the physical appearance has changed.

Balancing Chemical Reactions:

The Law of Conservation of Matter states that in a chemical reaction matter can neither be created or destroyed. Therefore, a chemical reaction must have the same number of atoms for each element on both sides of the equation. When this occurs, the equation is said to be balanced.

To balance chemical equation, coefficients (whole numbers) are placed in front of the chemical formulas. The coefficients should be in the lowest possible ratios. Sometimes it is just a method of trial and error to balance an equation.

Types of Chemical Reactions:

Most chemical reactions can be classified as to one of several types. The common types of chemical reactions are:

 

  1. In the combination reaction, two or more reactants combine to form a single product. A + B        AB

  2. In the decomposition reaction, a single reactants splits into two or more products. AB       A + B

  3. In the single replacement reaction, one element of a reactant replaces an element of a second reactant.

AB + C         B + AC

  1. In the double replacement reaction, the cations of two ionic reactants "switch" places. AB + CD       AD + CB

  2. In the combustion reaction, oxygen combines with a reactant (or fuel). Combustion reactions are sometimes combination reactions as well.  

Pre-lab:
bullet

Read the introductory material on the webpage.

bullet

Read Experiment Six in the laboratory manual.

bullet

Answer the pre-lab study questions  for Experiment Six

bullet

You are encouraged to do part B and the Application Questions at the end of Experiment Five before coming to lab.

Additional Problems:

  1. Balance the following equations:

NaOH + H3PO4 ®  Na3PO4 + H2O

C2H6 + O2 ® CO2 + H2O

(NH4)2SO4 + NaOH ® NH3 + H2O + Na2SO4

  1. Classify the following reactions:

2Fe + 3Cl2 ® 2 FeCl3

2AgNO3 + K2SO4 ® Ag2SO4 + 2 KNO3

K2CO3 ® K2O + CO2

  1. To which type of reaction (as discussed in lab) is each of the following statements referring? There may be more than one answer for each statement.

An element is a reactant.

An element is a product.

A compound is a reactant.

A compound is a product.

  1. Answer Question 6.83 on page 17*9 of your McMurray textbook.

Supplies and Chemicals:

bullet Magnesium ribbon (2-3 cm)
bulletZinc strips (1 cm square)
bullet1 M CuSO4
bulletCu pieces (1 cm square)
bullet 1 M HCl
bulletCuCO3
bulletH2O2
bulletMnO2
bullet0.1 M NaCl
bullet0.1 M AgNO3
bullet6 M HNO3
bullet0.1 M Na2SO4
bullet0.1 M Cu(NO3)2
bullet 0.1 M NaOH
bulletphenolphthalein solution
bulletwood splints
bullettest tubes

 

Safety Precautions:

SAFETY GOGGLES MUST BE WORN AT ALL TIMES DURING THE LAB.

HCl is a corrosive acid. Handle with care. Clean up spills immediately. If skin contact occurs, rinse the area with water for a minimum of 10 minutes.

Waste Disposal Instructions:

Wastes containing copper salts should be placed in container marked "Copper Waste".

Pour other liquid wastes down the sink followed by large amounts of water.

Place solid wastes in the trash cans.