Download Chemical Reactions

Chemical Reactions
Purpose:
In this lab you will perform chemical reactions. You should be able to use your
data to determine the type of reactants and the products produced. Throughout the lab
you should identify key components to conclude that a chemical reaction has taken place.
Objectives:
- To observe some chemical reactions and identify reactants and products of those
reactions.
- To classify reactions as to type and write symbols showing phases.
- To practice and learn the splint test for gases.
Pre-Lab Discussion:
There are many kinds of chemical reactions and several ways to classify them.
One useful method of classifies reactions into four major types. These are: 1.) synthesis;
2.) decomposition; 3.) single replacement; and 4.) double replacement reactions. Not all
reactions can be put into one of these categories. Many, however, can.
In a synthesis reaction two or more substances combine to form a more complex
substance. A decomposition reaction is the opposite of synthesis and breaks down a
compound into two or more substances. In a single replacement reaction, one substance
in a compound is replaced by another, more active, substance (an element). In a double
replacement reaction, the metal ions of two different ionic compounds can be thought of
as “replacing one another.” Most replacement reactions, both single and double, take
place in aqueous solutions contain free ions. In double replacement reaction, one of the
products is a precipitate, an insoluble gas, or water.
All types of reaction discussed here may be represented by balanced molecular
equations. Reactions involving ion exchange may be represented by ionic equations. In
this investigation you will be concerned only with molecular formulas and equations. In
balanced equations, the number of atoms of any given element must be the same on both
sides of the equation. Multiplying the coefficient and the subscript of an element must
yield the same result on both sides of the balanced equation.
In this investigation you will observe examples of the four types of reactions
described above. You will need to use your data to identify the reaction type and then
predict the products. Finally you will balance the equation and identify how you know
that a chemical reaction has occurred.
Wood Split Test Results:
You will also perform a splint tests to determine the gas produced. The tests are
performed by placing burning or glowing wood splints into a test tube where the gases
may be present; the results will differ based on the gas present as described here:
gas
CO2
H2
O2
test and result
a burning splint is put out
a burning splint causes a small explosion (a loud “pop” or “SQWARK”) in
forming water
a burning splint burns more brightly; a glowing splint bursts into flame
(maybe making a soft “pop”)
SAFETY: Wear goggles, gloves, and aprons when working with chemicals. Read
safety notes for each experiment before performing it!
Procedure:
Part 1:
1. Place 5mL of 3.0M aqueous hydrochloric acid in a test tube. BE CAREFUL NOT
TO SPILL THE ACID.
2. Add 2-3 cm piece of magnesium ribbon to the acid. Make and record Observations.
3. Place another test tube over mouth of the test tube containing the acid and
magnesium (the mouths should be the same sixe).
4. After the reaction is finished, light a wooden splint. Quickly turn over the top test
tube (so the mouth is pointing up) and place the burning wood splint near the mouth
of the collecting tube. (DO NOT PLACE THE SPLINT NEAR THE MOUTH
OF THE REACTION TUBE And DO NOT POINT THE TEST TUBE
TOWARD ANYONE) Also be prepared for a loud sound, so that you do not drop
your test tube. Make and record observations.
Data Part 1:
Observation of reactants before:
During reaction:
Observation of products
Hydrochloric acid
Magnesium ribbon
What type of chemical reaction has taken place?
What products are produced?
Write the balanced chemical equation for the reaction in Part 1:
Part 2:
1. Examine a piece of magnesium ribbon about 1-2 cm in length.
2. Light the Bunsen burner
3. Use tongs to hold 1 cm piece of magnesium ribbon in the flame. DO NOT LOOK
DIRECTLY AT THE MAGNESIUM AS IT BURNS. Make and record your
observations.
Data Part 2
Observation of Reactants Before
During reaction
Products after reaction
Magnesium ribbon
What does magnesium react with in the air?
What type of chemical reaction is this?
What products are produced?
Write the balanced chemical reaction for the chemical reaction in part 2.
Part 3:
1. Place 2 heaping microspatulas of copper (II) carbonate in a clean, dry test tube.
Record your observations in the data section.
2. Using a test tube holder, heat the copper (II) carbonate strongly for about 3
minutes. Extinguish the flame and then insert a burning wood splint into the test
tube. If carbon dioxide gas is present, it will put the flame out. Note any changes
in appearance of the residue in the test tube.
Data Part 3:
Observation of Reactants Before
During reaction
Products after reaction
Copper (II) Carbonate
What type of chemical reaction is this?
What products are produced?
Write the balanced chemical reaction for the chemical reaction in part 3.
Conclusion:
1. For each of the reactions, what observations indicated a chemical reaction was
taking place?
2. For each reaction identify the type of chemical reaction and how you can identify
that it is this type?
3. List three chemical reactions from everyday life; explain how your examples
indicate a chemical reaction is occurring.