Determination of empirical formula lab report

3. Labeled Sketch of the Apparatus:

2. Data Processing and Presentation:

1. Calculation of the Mass of Magnesium Ribbon:

m (Mg) = m (crucible + lid + Mg) – m (crucible + lid)

         = 15.336 – 15.313 =

 = 0.023 ± 0.002 g

2. Calculation of the Mass of Magnesium Oxide:

m (MgxOy) = m (crucible + lid + combustion product) – m (crucible + lid)

               = 15.351 – 15.313

               = 0.038 ± 0.002 g

3. Calculation of the Mass of Oxygen In the Magnesium Oxide:

m (O) = m (MgxOy) – m (Mg)

           = 0.038 – 0.023

           = 0.015 ± 0.004 g

4. Calculation of the Moles of Oxygen and Magnesium:

n (Mg) = m (Mg) ÷ M(Mg)

        = 0.023 g ÷ 24.31 g.mol-1

        = 0.00095 mol (uncertainty to be found in the next question)

n (O) = m (O) ÷ M (O)

          = 0.015 g ÷ 16.00 g.mol-1

          = 0.0009 mol (uncertainty to be found in the next question)

5. Determination of Uncertainties In Moles:

Since the molar mass is a definitional quantity, its uncertainty is zero, thus:

Δn (Mg) = 1/24.31 (± 0.002) = ± 0.00008 mol

Δn (O) = 1/16.00 (± 0.004) = ± 0.0003 mol

Table 2: Quantities of the oxide and its constituting elements

6. Calculation of the Empirical Formula:

Table 3: Calculation of the empirical formula

Thus the empirical formula is MgO.

2. Conclusion and Evaluation:

1. Conclusion:

• Researching the Empirical Formula of Magnesium Oxide:

Consulting , the empirical formula of magnesium oxide is MgO which is identical to the one I got.

• Differences and Roundings I Made:

When subtracting the masses, I didn’t round any results. However, when calculating the moles of Mg and O, I rounded my results to the corresponding number of decimal places in order to match their uncertainties.

2. Evaluating the Procedure:

• The Percentage of Purity of Initial Mg:

The initial reactant is not 100% pure Mg, otherwise the number of moles of both Mg and O would have been exactly equal, which is not the case.

• Side Reactions That Might Have Occurred:

• End of the Reaction:

After heating the crucible, its lid and the magnesium for almost 10-13 minutes, I noticed that gray powder was no longer forming so I decided that the reaction was over.

3. Improving the Investigation:

• The Bunsen Burner was not well functioning so it took us a lot of time to get to the perfect flame.
• When the magnesium began to bum, we didn’t remove the burner; we kept it until the end of the experiment which we shouldn’t have done.