Making Ionic Compounds
Elements combine to form compounds. If energy is released as the
compound is formed, the resulting product is more stable than the
reacting elements. In this investigation, you will react elements to
form two compounds. You will test the compounds to determine several of
their properties. Ionic compounds have properties that are different
from those of other compounds. You will decide if the products you
formed are ionic compounds.
Problem
What are the formulas and names of the products that are formed? Do the
properties of these compounds classify them as having ionic bonds?
Objectives
-
Observe evidence of a chemical reaction.
-
Acquire and analyze information that will enable you to
decide if a compound has an ionic bond.
-
Classify the products as ionic or not ionic.
Materials
magnesium ribbon
crucible
ring stand and ring
clay triangle
laboratory burner
stirring rod
crucible tongs
centigram balance
100-mL beaker
distilled water
conductivity tester
Safety Precautions
-
Always wear safety glasses and a lab apron.
-
Do not look directly at the burning magnesium. The intensity of the
light can damage your eyes.
-
Avoid handling heated materials until they have cooled.
Pre-Lab
-
Read the entire CHEMLAB. Identify the variable. List any
conditions that must be kept constant.
Variable: mass of Mg;
Constant: there must be an excess of oxygen
-
Write the electron configuration of the magnesium atom.
Mg 1s22s22p63s2
-
Based on this configuration, will magnesium lose or gain electrons
to become a magnesium ion?
lose electrons
-
Write the electron configuration of the magnesium ion.
Mg2
+ 1s22s22p6
-
The magnesium ion has an electron configuration like that of which
noble gas?
neon
-
Repeat question 2 for oxygen and nitrogen.
0 1s22s22p4,
N 1s22s22p3
a. Both will
gain electrons.
b. 02 - 1s22s22p6,
N3 - 1s22s22p3
c. Both
have the configuration of neon.
-
Use the data table in the next column.
-
In your data table, which mass values will be measured directly? Which
mass values will be calculated?
The mass of the magnesium
and the mass of the magnesium products are calculated. Other mass
values are measured directly.
-
Explain what must be done to calculate each mass value that is not
measured directly.
The mass of magnesium ribbon is
calculated by subtracting the mass of the crucible from the mass of
the crucible and magnesium. The mass of the magnesium products is
calculated by subtracting the mass of the crucible from the mass of
the crucible and its contents after heating.
Procedure
-
Arrange the ring on the ring stand so that it is about 7 cm above the
top of the Bunsen burner. Place the clay triangle on the ring.
-
Measure the mass of the clean, dry crucible, and record the mass in
the data table.
-
Roll 25 cm of magnesium ribbon into a loose ball. Place it in the
crucible. Measure the mass of the magnesium and crucible and record
this mass in the data table.
-
Place the crucible on the clay ring. Heat the crucible with a hot
flame, being careful to position the crucible near the top of the
flame.
-
When the magnesium metal ignites and begins to burn with a bright
white light, immediately turn off the laboratory burner.CAUTION:
Do not look directly at the burning magnesium. After the
magnesium product and crucible have cooled, measure their mass and
record it in the data table.
-
Place the dry solid product in a small beaker for further testing.
-
Add 10 mL of distilled water to the dry magnesium product in the
beaker and stir. Check the mixture with a conductivity checker, and
record your results.
Sample Data
Mass Data
|
Material(s)
|
Mass (g)
|
Empty crucible
|
7.65g
|
Crucible and Mg ribbon before heating
|
7.85 g
|
Magnesium ribbon
|
0.20 g
|
Crucible and magnesium products after heating
|
7.93 g
|
Magnesium products
|
0.28 g
|
Cleanup and Disposal
-
Wash out the crucible with water.
-
Dispose of the product as directed by your teacher.
-
Return all lab equipment to its proper place.
Analyze and Conclude
-
Analyzing Data Use the masses in the table to calculate the
mass of the magnesium ribbon and the mass of the magnesium product.
Record these masses in the table.
-
Classifying What kind of energy was released by the reaction?
What can you conclude about the product of this reaction?
Heat
and light; It is more stable than the reacting elements.
-
Using Numbers How do you know that the magnesium metal reacts
with certain components of the air?
There is an increase in
mass from 0.20 g to 0.28 g.
-
Predicting Magnesium reacts with both oxygen and nitrogen from
the air at the high temperature of the crucible. Predict the binary
formulas for both products. Write the names of these two compounds.
Mg0,
magnesium oxide; Mg3n2
-
Analyzing and Concluding The product formed from magnesium and
oxygen is white, and the product formed from magnesium and nitrogen is
yellow. From your observations, which compound makes up most of the
product?
MgO; the product appears white.
-
Analyzing and Concluding Did the magnesium compounds and water
conduct an electric current? Do the results indicate whether or not
the compounds are ionic?
Yes; ionic compounds conduct a
current in solution.
-
Error Analysis If the magnesium lost mass instead of gaining
mass, what do you think was a possible source of the error?
Possible
answers include that some of the product blew away or that the
reaction was incomplete.
Real-World Chemistry
-
The magnesium ion plays an important role in a person's biochemistry.
Research the role of this electrolyte in your physical and mental
health. Is magnesium listed as a component in a multivitamin and
mineral tablet?
Answers may include that it is important in
nerve impulse transmission. Mg is present in vitamin-mineral tablets.
-
Research the use of Mg(OH)2in everyday products. What is
Mg(OH)2commonly called in over-the-counter drugs?
Answers
might include that it is used in over-the-counter antacids and
laxatives, where it is known as milk of magnesia.