One objective was to figure out if the burnt Mg ashes weigh more than the product which is Magnesium Metal. Another objective was determining the formula of the compound that results when Magnesium and Oxygen react. Theory:
The purpose of this lab was to confirm the chemical formula of magnesium oxide by comparing the masses of pure magnesium solid prior to any reaction and magnesium oxide solid after a reaction between all of the magnesium and oxygen from the air when heated from a Bunsen burner in a crucible. Using molar masses of both magnesium and oxygen, an expected percent composition, by mass, was found and compared to our experimental results. Experimental:
Setup ring stand
Obtain desired amount of Magnesium which was 2g
Weigh the crucible, 13.52g
Weigh the crucible with the lead, 15.51g
Heat the crucible with the Mg present
Continue to heat until lead starts to change to an ash color, lead should start turning very bright 7.
Shut burner down and let the Mg cool
Add water to the Mg until the crackling and smoking stops (Mg3N2+MgO) (Mg3N2->H2O->MgO+NH3) - Ammonia 9.
Now, heat crucible till the water evaporates
Allow a few minutes for cooling
Weigh the crucible along with the Mg ashes, 16.34g
To find the formula of magnesium oxide, you need the mass of the magnesium and the mass of the oxygen. Also the atomic masses. Magnesium is 24 and oxygen is 16. Divide mass by the atomic mass for each element. This gives the number of moles of each. Having done this for both elements, you should find the ratio between the two by dividing them both by the smallest number. The ratio should be close to 1:1 as the formula of magnesium oxide is MgO. 2Mg + O2 2MgO
.08333molemg 2/2 .08333moleMgO
3.33gMgO should be in the crucible
The equation is:
Magnesium + oxygen → magnesium oxide
2Mg + O2 → 2MgO.
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