Chemistry Lab Handout 14 "Empirical Formula"

Your Name: ___________________________________ Role:______________

Lab Partners: ________________Role:_____ ________________Role:_____

Problem: How do you determine the empirical formula of Magnesium

oxide?

Hypothesis: _______________________________________________________

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Materials: crucible cover

tongs clay triangle ring clamp

ring stand Bunsen burner balance

magnesium      fiber pad

Caution:

Procedure:

1. Obtain goggles and wear them for the entire lab.

2. Screw the ring clamp to the ring stand and place the clay triangle on the ring.

3. Place a clean crucible, with the cover on but slightly opened, on the clay triangle and heat strongly for 3 minutes.

4. Only handle the lid and crucible with the tongs after step 2.

5. Let the crucible and cover cool on the fiber pad for 2 minutes.

6. Mass the crucible with cover and record to the nearest 0.001 g.

7. Coil an approximately 10 cm piece of Mg and place it at the bottom of the crucible.

8. Determine the mass of the crucible, cover and Mg and record.

9. Place the crucible with Mg, without the lid, on the clay triangle.

10. Heat strongly until the Mg ignites. As soon as the Mg begins to burn, use the tongs to place the cover on the crucible, and turn off the burner.

11. After the smoke has subsided, strongly heat for 5 more minutes. The cover should be ajar by about 0.5 cm during this time.

12. If any Mg ribbon remains, heat strongly for 5 more minutes.

13. When the product is a light gray powder, turn off the burner and allow the crucible, cover and product to cool for 5 minutes.

14. Using the tongs, place the crucible, cover and product on the balance and record the mass to the nearest 0.001 g.

Observations: (none)

Data:

Mass of empty crucible and cover:

Mass of crucible, cover and Mg:

Mass of crucible, cover and product:

Diagram:

Conclusion: _______________________________________________________

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Questions:

1. What was the mass of Mg you used?

2. What was the mass of product you obtained?

3. What was the mass of elemental Oxygen you synthesized to the Mg?

4. How many moles of Mg did you use?

5. How many moles of O did you use?

6. Calculate the ratio between moles of Mg used and moles of O used.

7. Express the ratio in the simplest whole number form and write the empirical formula for the Magnesium Oxide you formed.