Experimental Determination of the Formula of Magnesium Oxide.
Magnesium is a mental, it is known to react with oxygen. Magnesium reacts vigorously when heated in the presence of air, which is why we have chosen high heat in our method to facilitate combustion. This oxidation reaction produces magnesium oxide gaining oxygen from the air. When sharing of electrons occur a chemical bond is made and the atoms combine to form a molecule.
So, the predicted molecular formula:
Mg + O2---------> MgO2
Since the Mg combines with 2 atoms of oxygen we need to balance the equation:
2Mg + O2--------> 2MgO
This tells use that 2 moles of magnesium gives 2 moles of MgO. Ratio of 1:1 conversion.
So in theory, the number of moles calculated for magnesium should give the same number of moles of MgO.
Using the same balance for all weighing in this experiment.
Recorded the mass of a dry porcelain crucible and lid via an analytical balanced.
Obtained a length of pre-cut magnesium and cleaned with emery paper. Then coiled the ribbon around a pencil to ensure it is not wrapped too tightly, then placed into the bottom of the crucible.
Record the mass of the magnesium ribbon and crucible with lid via the same analytical balance.
Putting the crucible securely on the clay triangle. The lid set slightly off-centre on the crucible to allow air to enter but to prevent the magnesium oxide from escaping.
Heated the crucible at a high 'blue' flame from the Bunsen burner.
Checked the magnesium intermittently, until all the magnesium turned into a gray-white powder.
Allowed to cool and record the mass of the end product, crucible plus lid with the same analytical scales as previous.
Mass of crucible + lid
Mass of crucible + lid + Mg
Mass of Mg
Mass of crucible + lid + MgO
Mass of MgO residue
Mass of oxygen that combined with Mg
Please join StudyMode to read the full document