# Empirical Formula Determination of Magnesium Oxide: Analysis, Errors, and Improvements

Categories: Chemistry

To determine the empirical formula of magnesium oxide by conducting a reaction between magnesium and oxygen.

#### Materials:

1. Magnesium ribbon
2. Crucible and cover
3. Bunsen burner
4. Crucible tongs
5. Analytical balance
6. Magnesium oxide product

#### Procedure:

1. Weighing Magnesium: a. Weigh an empty crucible and cover. b. Place a piece of magnesium ribbon in the crucible. c. Record the combined mass of the crucible, cover, and magnesium.
2. Heating Magnesium: a. Carefully cover the crucible. b. Heat the crucible with a Bunsen burner until the magnesium ignites.

c. Continue heating until the magnesium burns completely, leaving magnesium oxide.

3. Weighing Magnesium Oxide: a. Allow the crucible to cool. b. Weigh the crucible, cover, and magnesium oxide product.

#### Data Analysis:

1. Determine the mass of magnesium: Mass of Magnesium=Final mass−Initial massMass of Magnesium=Final mass−Initial mass
2. Determine the moles of magnesium: Moles of Magnesium=Mass of MagnesiumMolar Mass of MgMoles of Magnesium=Molar Mass of MgMass of Magnesium​
3. Determine the moles of oxygen: Since magnesium oxide is formed by the reaction of magnesium and oxygen in a 1:1 ratio, Moles of Oxygen=Moles of MagnesiumMoles of Oxygen=Moles of Magnesium

The empirical formula is determined by the ratio of moles of magnesium to moles of oxygen.

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Conclusion:
Based on the experimental data, determine the empirical formula of magnesium oxide.

Remember, the molar mass of magnesium (Mg) is approximately 24.31 g/mol, and the molar mass of oxygen (O) is approximately 16.00 g/mol.

Make sure to follow all safety protocols and guidelines while conducting the experiment.

PROCEDURE

1. Weigh a clean and dry crucible along with its lid.

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2. Clean the magnesium ribbon using sandpaper, form it into a tight coil, place it in the crucible, and re-weigh the crucible with magnesium and the lid.
3. Position the crucible on the clay triangle over the tripod and strongly heat the crucible.
4. After a few minutes, observe the crucible's contents. If the magnesium does not seem to be burning, increase the heat. Minimize the escape of white smoke, which represents magnesium oxide, to retain it for subsequent weighing.
5. Cover the crucible and continue heating for a few more minutes before rechecking.
6. Allow the crucible and its contents to cool, then add a few drops of distilled water to the crucible's contents. Heat the mixture strongly.
7. Once all magnesium is seemingly converted to oxide, turn off the burner and let the crucible cool.

Table 1: Qualitative data – experimental observations

 Observations Reactant  Magnesium metal Thin, silver, shiny solid During the reaction White smoke and white light was produced Product  Magnesium oxide Grey, powdery solid

Table 2: Quantitative data – experimental data

 Mass (g) Absolute Uncertainty (±g) Mass of crucible and lid 20.2029 ±0.0005 Mass of crucible, lid and magnesium 20.3993 ±0.0005 Mass of crucible, lid and magnesium oxide 20.5090 ±0.0005 Mass of magnesium 0.1964 ±0.0010 Mass of magnesium oxide 0.3061 ±0.0010

Mass calculations:

Mass of Mg = (mass of crucible, lid and Mg) – (mass of crucible and lid) = (20.3993) – (20.2029) = 0.1964

Mass of Magnesium oxide = (mass of crucible, lid and magnesium oxide) – (mass of crucible and lid)

= (20.5090 – 20.2029)

= 0.3061

Mass of O in Magnesium oxide = (mass of crucible, lid and magnesium oxide) – (mass of crucible, lid and Mg) = (20.5090) – (20.3993) = 0.1097

Absolute uncertainty calculations:

Uncertainty in Mg = uncertainty in (mass of crucible, lid and Mg) + uncertainty in (mass of crucible and lid) = 0.0005 + 0.0005 = 0.0010

Uncertainty in Magnesium oxide = uncertainty in (mass of crucible, lid and magnesium oxide) + uncertainty in (mass of crucible and lid) = 0.0005 + 0.0005 = 0.0010

Uncertainty in O = uncertainty in (mass of crucible, lid and magnesium oxide) + uncertainty in (mass of crucible, lid and Mg) = 0.0005 + 0.0005 = 0.0010

DATA PROCESSING

Empirical formula calculations:

 Mg O Masses (g) 0.19640.0010 0.10970.0010 Moles (mol) 0.0010 0.0010 Divide by smallest Simplest whole number ratio

However, there is an absence of uncertainty in molar masses, leading to no percentage error in this regard. Consequently, the percentage error in moles is equivalent to the percentage error in masses.

Therefore, the Mg:O ratio is determined as 1.178 ± 0.01673 : 1.

Conclusion:

Following the experiment and the subsequent data analysis, the derived empirical formula is Mg₁.₁₇₈ ± 0.₀₀₁₆₇₃O. However, the expected empirical formula for magnesium oxide is MgO, indicating a 1:1 ratio. The experimentally determined ratio deviates from this, suggesting systematic errors unaccounted for in the error analysis.

Evaluation:

1. Evaluation of Experimental Method - Monitoring the Reaction: The method involved lifting the crucible lid to check the reaction progress. This led to a higher Mg:O ratio, possibly due to MgO escaping as smoke. To minimize this, increasing the checking interval to five minutes could reduce product loss.
2. Evaluation of Experimental Method - Magnesium Reactivity: Some magnesium didn't react, likely due to coiling too tightly. Using powdered magnesium could increase the surface area, promoting better reaction efficiency.
3. Possible Instrumental Error Evaluation: Instrumental inaccuracies, especially in weighing, might contribute to discrepancies. To improve, weight readings could be repeated, and measurements of hot crucibles could be delayed to ensure accuracy.

In summary, there were significant shortcomings in the experimental design, with improvements suggested to address identified limitations and enhance the reliability of results.

Updated: Feb 29, 2024