Empirical Formula of Magnesium Oxide Experiment Report

Introduction

The purpose of this experiment was to determine the empirical formula of magnesium oxide (MgO) through combustion analysis. This involved burning magnesium in the presence of oxygen to form magnesium oxide and then analyzing the resulting mass data to calculate the empirical formula of the compound.

Experimental Procedure

The experiment was conducted in three trials, with the first two trials considered for analysis. The third trial was excluded due to the absence of recorded mass data after combustion.

Uncertainty Calculations

The uncertainties for the masses in both tables were determined to be 0.

02 g, calculated as the sum of the uncertainties in the initial mass of magnesium (0.01 g) and the initial mass of the crucible (0.01 g).

Table One: Uncertainty Calculations for Magnesium

The percent uncertainty for the mass of magnesium was calculated as 20% due to the 0.02 g uncertainty in mass.

Therefore, the uncertainty for the number of moles of magnesium was determined to be ±0.

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000823 mol.

Table Two: Uncertainty Calculations for Oxygen

The percent uncertainty for the mass of oxygen was calculated as 29% due to the 0.02 g uncertainty in mass.

Therefore, the uncertainty for the number of moles of oxygen was determined to be ±0.001269 mol.

Analysis

After calculating the uncertainties for the moles of both magnesium and oxygen, the uncertainties for the simplest ratios were deemed not relevant and were not calculated.

The percent error for the first trial was found to be 6%.

Unfortunately, data for the percent error in the second trial is not provided in the report.

Conclusion

The empirical formula for magnesium oxide is determined to be MgO based on the closest whole number ratio of moles of magnesium to moles of oxygen. However, it is noted that in one of the trials, the empirical formula was determined as Mg6O5, which is relatively close to MgO.

Although the percent error for the second experiment appears to be large, it is believed to be influenced by the very small mass values involved in the experiment. The empirical formulas derived from the data suggest that the data is more accurate. However, it is essential to acknowledge that the accuracy of the data decreased with each trial, possibly due to residual magnesium oxide in the crucible from the first trial.

Human error did not play a significant role in this experiment since all measurements were taken with digital instruments. Therefore, the errors in this lab are mainly systematic, potentially caused by incomplete combustion or the presence of impurities in the magnesium ribbon despite cleaning with steel wool.

Recommendations for Improvement

To improve the accuracy and reliability of future experiments, the following steps can be taken:

1. Use a more accurate scale, especially considering the small values involved in the experiment.
2. Ensure thorough cleaning of the crucible or use a new crucible to prevent errors from residual magnesium oxide.
3. Conduct the experiment multiple times to assess the impact of crucible cleaning on the results.
4. Maximize exposure of magnesium to oxygen to minimize incomplete combustion.
5. Consider the possibility of impurities in the magnesium ribbon and take measures to ensure sample purity.