Magnesium Oxide Lab Notes

Magnesium Oxide Lab

Introduction: Determining the Empirical Formula of Magnesium Oxide

This experiment aims to determine the empirical formula of magnesium oxide by reacting magnesium metal with oxygen and analyzing the mass changes. The empirical formula represents the simplest whole-number ratio of atoms in a compound.

• Empirical Formula: The simplest ratio of atoms in a compound.

• Possible Formulas for Magnesium Oxide: MgO, Mg2O, MgO2, Mg3O2

• Key Principle: The ratio of grams of magnesium to grams of oxygen is used to determine the empirical formula.

• Calculation Strategy: Convert grams to moles, then calculate the simplest whole-number ratio to determine the empirical formula.

Experimental Plan

1. Record the mass of magnesium.

2. Record the mass of the crucible and lid.

3. Burn magnesium in the crucible until the reaction is complete.

4. Record the mass of magnesium oxide, crucible, and lid after the reaction.

Data Collection

• Mass of Mg: 0.06 g

• Mass of Crucible + Lid: 23.75 g

• Mass of Crucible + Lid + MgO: 23.82 g

• Mass of MgO (product): 23.82 g - 23.75 g = 0.07 g

Calculations

• Mass of Mg reacted: 0.06 g

• Mass of O reacted: 0.07 g (MgO) - 0.06 g (Mg) = 0.01 g

• Moles of Mg reacted: $\frac{0.06\ \text{g}}{24.31\ \text{g/mol}} = 0.00247\ \text{mol}$

• Moles of O reacted: $\frac{0.01\ \text{g}}{16.00\ \text{g/mol}} = 0.000625\ \text{mol}$

• Ratio of Mg to O: $\frac{0.00247}{0.000625} \approx 3.952 \approx 4$

• Empirical Formula: Mg4O (but should be MgO; see sources of error)

Analysis and Discussion

• Theoretical Empirical Formula: MgO (1:1 ratio of Mg to O atoms)

• Experimental Ratio: The calculated ratio is higher than expected, indicating possible experimental error.

Sources of Error

• Oxygen Mass Too High: If the lid was not properly sealed, extra oxygen could have entered, increasing the measured mass of oxygen.

• Oxygen Mass Too Low: If MgO escaped through the opening in the lid, the measured mass of MgO would be less than it should be, making the calculated oxygen mass too low and the Mg:O ratio too high.

Summary Table: Key Data and Calculations

Measurement	Value	Calculation
Mass of Mg	0.06 g	Given
Mass of O	0.01 g	0.07 g (MgO) - 0.06 g (Mg)
Moles of Mg	0.00247 mol	$\frac{0.06}{24.31}$
Moles of O	0.000625 mol	$\frac{0.01}{16.00}$
Mg:O Ratio	~4:1	$\frac{0.00247}{0.000625}$

Conclusion

• The empirical formula for magnesium oxide is expected to be MgO, but experimental errors can affect the calculated ratio.

• Careful measurement and control of experimental conditions are essential for accurate results.

Additional info: The actual empirical formula for magnesium oxide is MgO, as magnesium and oxygen combine in a 1:1 molar ratio. Deviations in the experiment are likely due to procedural errors such as incomplete reaction, loss of product, or contamination.