The purpose of this lab was to determine the empirical formula of a compound. The experiment was conducted by burning magnesium in air resulting in the formation of magnesium oxide and magnesium nitride. The magnesium nitride was converted to magnesium hydroxide and ammonia after adding water, and after heating the magnesium hydroxide, it was converted to magnesium oxide.
The results of the experiment show that the empirical formula of magnesium oxide is Mg2O, but the theoretical empirical formula is MgO. The results showed that experimental error could have been a major factor in the determination of the end results.
If some unreacted magnesium metal remains in the crucible, the empirical formula will be affected. There will not be an accurate measurement of the MgO because the unreacted MgO will be included. If there is insufficient oxygen from the air, some magnesium nitride will form, but if it is not converted to magnesium oxide, the ratio of oxygen to magnesium will appear to be high. This is because you are assuming you will only have magnesium oxide present afterwards instead of both. In recalling the smell sensed when wafting the substance, I have smelled ammonia in various cleaning products in the past.
In order to calculate the stoichiometric ratio between the magnesium and oxygen in the magnesium oxide, the number of moles of oxygen from the increased mass of the sample had to be used.
Water was added to the sample and the sample was reheated because water acts as a catalyst in the reaction, meaning it "speeds up" the reaction.
If another experiment was conducted and 1.5 moles of Magnesium and 1 mole of Oxygen were obtained as the empirical formula, various sources of error could have been the reason for this. If there was unreacted metal or unreacted magnesium nitride left at the end of the experiment, this could have caused a change in the molar ratio of the formula. Also, if some of the sample stuck on the paper clip used for mixing, this may have changed the results. More trials could have been conducted which would make the results more precise in possible future experiments.
After the heating process, unreacted magnesium may remain due to the presence of nitrogen. A byproduct of magnesium nitride forms if this nitrogen is present.