Lab: Synthesis of Magnesium Oxide
I.
Purpose: The purpose of this lab is to determine the
percentage (by mass) of magnesium in magnesium oxide.
II.
Procedure:
1.
Obtain a strip of
magnesium ribbon that is about 20. cm long and determine its
mass.
2.
Coil the magnesium
ribbon up into a loose coil and place it flat in the bottom of your
crucible. If the coil is too tight you
won't get sufficient oxygen inside the coil to completely react with the
magnesium.
3.
(I won't always advise
you to the extent that I am in this lab.
For example, at this point in this lab you need to record the mass of
your crucible and its cover. I'm telling
you this now so that you are able to get good results from this lab, but for
future labs you are on your own. You
need to make sure that you think each lab procedure through thoroughly.)
4.
Set up a ring stand
assembly and place a ceramic triangle on the iron ring. Place the crucible in the ceramic
triangle. Place the cover on the
crucible and heat the crucible strongly for several minutes. Lift the cover every few seconds to allow
more air into the crucible. Try not to
let any smoke escape.
5.
When you can remove
the cover completely without any smoke escaping, heat the crucible strongly
with the cover off for one minute. (If smoke does start to escape, put the
cover back on and go back to step 4.
6.
Allow the crucible to
cool for 4 minutes with the cover off, then squirt
several drops of distilled water onto the solid inside the crucible until it is
fully moist. As you do
this carefully try to smell any odor that emanates from the
crucible. What is it that causes that
odor? How did it get there? You must figure out the answers to these
questions and discuss this in your lab report to show that you understand
exactly what has happened.
7.
Place the cover on the
crucible and heat the crucible strongly for several minutes. Lift the cover every few seconds to allow
more air into the crucible. Try not to
let any smoke escape.
8.
When you can remove
the cover completely without any smoke escaping, heat the crucible strongly
with the cover off for one minute.
9.
Allow the crucible to
cool for 5 minutes, then carefully determine the mass
of the magnesium oxide product, the crucible and its cover.
10.
Record your data.
III.
Data:
(Create a
data table per the Lab Report Format handout.)
IV.
Calculations:
Show an
example calculation using your own data to determine the percentage of Mg in MgO.
V.
Conclusion:
Based on
your data and your classmates' data, what is the percent of Mg in MgO. How consistent were your results with the
results among your classmates. Does this
lab verify the Law of Definite Composition?
VI.
Error Analysis:
The
actual percent of Mg in MgO is 60.3%. Do a percent error calculation for your data
and for your class average.
Write an
enumerated list of the sources of error that were present in this lab.