Determination of Moles in Magnesium Oxide

Calculations

1. Find the number of moles present in the oxide.

.019 moles of oxide

2. Find the number of moles present in the oxide.

.019 moles of oxide

3. Find the empirical formula for magnesium oxide.

Mg O

4. Find the mass percent of magnesium and of oxygen in magnesium oxide.

Analysis

1. Suppose a student transferred the crucible containing the magnesium oxide and the lid to the scale with his/her hands after it cooled. What effect could this have on the calculated ratio of moles of magnesium to moles of oxygen, Mg:O? Justify your answer.

If the student grabbed the crucible with his or her hands, the ratio of moles of magnesium to oxide would be larger because the touch with the hands would’ve transferred dirt and oils to the crucible, hence, increasing the weight of the magnesium and altering the number of moles of oxygen..

2. Suppose a student allowed a significant amount of white smoke to escape while heating the magnesium ribbon. What effect would this have had on the calculated number of moles of oxygen? Explain.

3. A student performs the experiment, but fails to remove the tarnished material on the outside of the magnesium ribbon with steel wool.

a. What is the tarnished material? Magnesium Oxide

b. What effect would this have had on the calculated number of moles of magnesium? Explain.

The number of moles would have been greater, and the ratio of one to one would no longer be. This is because the tarnished material would have heated up with the magnesium and mixed with it inside the crucible, so