Magnesium oxide

Research Question: To determine the empirical formula of magnesium oxide.

Data collection and processing

Qualitative data: After heating the magnesium strongly for few minutes the ribbon began to melt and glowed with a bright white light. Lifting the lid caused the magnesium to glow even more brightly and white smoke formed that escaped from the crucible. After some time the smoke stopped escaping and the magnesium turned to a grayish-white powder that no longer glowed with a bright light.

Data collection:

Mass of crucible + lid: 32.450g

Mass of crucible + lid + Mg: 32.900g

Mass of crucible + lid + Magnesium oxide: 33.160g

Processed Data:

Mass (in grams)


Crucible, lid


+/- 0.005

Crucible, lid, Magnesium


+/- 0.005

Crucible, lid and

Magnesium oxide


+/- 0.005


(Mass of Crucible, lid and Magnesium - Mass of Crucible and lid)


+/- 0.01

Magnesium Oxide

(Mass of Crucible, lid and Magnesium Oxide - Mass of Crucible and lid)


+/- 0.01


(Mass of Magnesium Oxide - Mass of Magnesium)


+/- 0.02


Empirical formula:




0.450g +/- 0.01

0.260g +/- 0.02.

Molar Mass



No. Of Moles

= Mass/Molar mass

= 0.450/24.31

= 0.01851

= Mass/Molar mass

= 0.260/16.00

= 0.01625




Final ratio



Approximately equal to



Empirical formula


% Uncertainty of Magnesium = Error in balance *100

Mass of magnesium

= 0.01*100/0.450

= 2.22%

Conclusion and Evaluation:

Interpretation of data using calculated result: The empirical formula of magnesium oxide, under the prevailing laboratory conditions, is 1.14:1, unlike the actual empirical formula, which is 1:1.

Percentage deviation = ½1.14-1/1½*100

= 14%

Evaluation of weakness

1. Random uncertainties because of the limitations of the instruments are likely to be the cause of the difference in the empirical formula.

2. The high temperatures may have caused the crucible to react with the magnesium.

3. The magnesium was burned in air not pure oxygen. Magnesium may have also reacted with other gases in air. Like it may have reacted with Nitrogen to give Magnesium Nitride.

4. The Magnesium is impure causing formation of other products that will increase the mass.

5. Lifting the lid may have caused some of the products to escape in the air.

6. Measuring the crucible with Magnesium oxide while it was still hot may have lead to an error in the reading, as the products would have expanded weighing heavier than they are.

Suggesting improvement in method with respect to weakness and limitations

1. Pure Magnesium obtained my scraping of Magnesium should be used so that no other product other than that of Magnesium is formed.

2. The weight readings could be taken twice to avoid uncertainties.

3. A better method should be used to allow the air to pass into the crucible when the Mg is being heated.

4. The cooling of the heated Mg pieces should be done for a specific time, as it would change the readings.

5. Pure Oxygen should be supplied rather than air. So that less of other products are formed.

6. A stronger crucible should be used so that it does not react during high temperatures.

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