Lab:� Synthesis of Magnesium Oxide
- Purpose:� The purpose of this lab is to determine the percentage (by mass) of magnesium in magnesium oxide.
- Obtain a strip of magnesium ribbon that is about 20. cm long and determine its mass.
- 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.
- (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.)
- 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.
- 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.
- 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.
- 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.
- When you can remove the cover completely without any smoke escaping, heat the crucible strongly with the cover off for one minute.
- Allow the crucible to cool for 5 minutes, then carefully determine the mass of the magnesium oxide product, the crucible and its cover.
- Record your data.
(Create a data table per the Lab Report Format handout.)
Show an example calculation using your own data to determine the percentage of Mg in MgO.
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?
- 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.