Ray Yuan
Lab Partner:Rithik Rajani
Date: June 26,2015

Determining the Empirical Formula of Magnesium Oxide

Design Part:
Background/Introduction:
Empirical formula is defined as the simplest whole number ratio of the elements in a compound. In this experiment, the reaction between magnesium metal and oxygen gas will be observed. When heated, magnesium reacts readily with oxygen in the air to form magnesium oxide. By determining the mass of the reactants and products in the experiment, one will be able to determine the moles involved in the reaction. Success is best defined as obtaining a product yield close to 100%.
Objective:
The objective of the lab was to calculate the mass of magnesium oxide and perform a synthesis reaction between magnesium and oxygen, which would lead to finding the empirical formula of magnesium oxide.
Hypothesis:
If Magnesium Oxide is the chemical formula,then the empirical formula is MgO because it is the lowest ratio of atoms of. Magnesium and Oxygen.
Materials and Equipment:
15 cm magnesium ribbon,2
25 mL beaker
Bunsen burner assembly clay triangle crucible and lid, metal or ceramic crucible tongs distilled water eyedropper or micropipet ring stand

Procedure:
1. The crucible was put on the clay triangle on a ringstand, and a bunsen burner was placed under it.
2. the crucible was heated for 5 minutes.
3. the crucible was cooled to room temperature, and the mass of the crucible and lid was taken and recorded.
4. A 15cm strip of magnesium was polished and cut into small pieces and placed into the crucible.
5. The mass of the crucible , lid, and metal(magnesium) was then measured and recorded.
6. The crucible was then put on the ringstand and heated with the bunsen burner, with the lid being lifted occasionally .
7. When the magnesium was fully reacted(all white/gray powder), the crucible lid was taken off and the crucible was allowed to continue heating for 1 minute.
8. The burner was turned off, and the crucible was waited on to cool. A few drops of distilled water were then added to the product in the crucible.
9. The lid was placed back on the crucible, and the entire thing was heated by the bunsen burner for another minute.
10. The bunsen burner was turned off and the crucible, lid and contents were cooled to room temperature. The mass of that was measured and recorded in the margin.
11. The crucible , lid , and product were reheated for another 2 minutes, cooled back to room temperature, and mass was taken again. The mass of this step was +-0.02% of the mass in step 10 , so it was permanently recorded in the data table.
12. lab station was cleaned.

Data and Calculations:

Qualitative data: while the crucible was being heated, the content inside was glowing a bright orange.
The silver magnesium strips slowly turned into silvery white powder.
When the lid was taken off during the heating, some ash floated from the crucible.
The bright orange light slowly got dimmer as the heating went on. there was still a little silver on the bottom of the crucible when the reaction was stopped.

Quantitative data: Data Table Of Recorded Masses

Trial 1
Mass of crucible, lid, and metal(g):initial
20.61
Mass of crucible, lid, and product(g):final
20.74
Mass of crucible and lid(g)
20.39

Calculations:
Mass of Magnesium Metal used:20.61g-20.39g=0.22g
Mass of the product:20.74g-20.39g=0.35g
Mass of oxygen consumed: 20.75g-20.61g=0.13g
Moles of Magnesium: 0.22g x =0.0090 mol Mg
Moles of Oxygen: 0.13g x =0.0081 mol O
Smallest whole-number mole ratio of atoms: : =1.1 mol Mg : 1.0 mol O

Results Table:

Element

Magnesium
Oxygen
Mass
0.22g
0.13g
Number of Moles
0.0090 mol Mg
0.0081 mol O
Ratio Exact(2 sig figs)
1.1
1.0
Ratio(estimate/approximate)
1
1
Empirical Formula of Magnesium Oxide
MgO

Conclusion and Evaluation: the overall purpose of this lab was to determine the Empirical Formula of Magnesium Oxide. The mass of the Magnesium used(0.22g) and mass of the Oxygen