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In chemistry, compounds can be distinguished by using the empirical formula, which provides the simplest positive integer ratio of elements in a compound. The empirical formula is particularly useful for identifying ionic compounds with a non-directional nature of bonding, where ions can be surrounded by various oppositely charged ions. This results in a repeating lattice structure of ions, making the empirical formula a valuable tool for defining ionic-bonded substances.
To calculate the empirical formula of a compound formed during a chemical reaction, follow these steps:
For example, the molecular formula of butane is C4H10, but the ratio of carbon to hydrogen atoms can be reduced to 2:5 to represent the empirical formula as C2H5.
A mole is the quantity of a substance that contains as many elementary units (atoms, ions, molecules) as there are atoms in exactly 12 grams of carbon-12 isotope.
A mole of an element is numerically equal to the element's atomic weight in grams.
For compounds, a mole is numerically equal to the molecular weight in grams. In simpler terms, a mole of a substance is its atomic/molecular weight in grams. For example, a mole of copper (atomic weight 63.6) is 63.6 grams.
The experiment involves the combustion of magnesium metal to determine the empirical formula of magnesium oxide. The setup includes the use of a crucible and Bunsen burner to heat the magnesium metal for burning.
The purpose of this experiment is to determine the empirical formula of magnesium oxide by performing the combustion of magnesium and collecting precise mass data.
Ensure safety during the experiment by wearing safety glasses to protect eyes from the intense UV light produced during the combustion of magnesium. Avoid inhaling the smoke produced when magnesium burns, as it can cause irritation. Use tongs to handle hot objects to prevent burns. Do not cool the crucible or lid under cold water immediately after heating, as it may cause cracking and potential injury.
Before Heating | After Heating | |
---|---|---|
Mass of Magnesium | 0.08g | n/a |
Mass of Oxygen | n/a | 0.05g |
Mass of Magnesium Oxide | n/a | 0.13g |
Mass of crucible + lid | 24.36g | 24.31g |
n/a (To be calculated)
24.39g (To be calculated)
Mass of Mg in 1 mole / Mass of MgO in 1 mole (To be calculated)
Mass of O in 1 mole / Mass of MgO in 1 mole (To be calculated)
Upon observation, the 5cm magnesium ribbon had a slightly greasy texture and a brittle and coarse surface. After cleaning its surface thoroughly with steel wool, it became shiny and glossy, no longer feeling waxy. The purpose of this cleaning was to remove the oxide layer on the magnesium ribbon's surface, which can hinder combustion. The crucible and lid were also cleaned by firing them under a blue Bunsen flame to remove any contaminants and moisture.
In this experiment, the combustion of magnesium with oxygen produced magnesium oxide. The balanced chemical equation is: 2Mg(s) + O2(g) → 2MgO(s)
To calculate the mass of each substance, we use the following formulas:
Mass of Magnesium = Mass 2 - Mass 1 = 24.39g - 24.31g = 0.08g
Mass of Oxygen = Mass 3 - Mass 2 = 24.44g - 24.39g = 0.05g
Mass of Magnesium Oxide = Mass 3 - Mass 1 = 24.44g - 24.31g = 0.13g
Now, we can calculate the number of moles using the formula: Number of Moles = Mass / Molar Mass
Number of Moles of Magnesium: N = 0.08g / 24.31g/mol = 0.0033 moles (rounded to 4 decimal places)
Number of Moles of Oxygen: N = 0.05g / (16g/mol * 2) = 0.0016 moles (rounded to 4 decimal places)
Divide by the smallest mole value (Oxygen):
Magnesium Mole ratio = 0.0033 / 0.0016 ≈ 2.06
Oxygen Mole ratio = 0.0016 / 0.0016 = 1
Rounding to the nearest whole number:
Magnesium Mole ratio = 2
Oxygen Mole ratio = 1
So, the empirical formula for magnesium oxide is MgO, which matches the theoretical formula.
The experiment successfully demonstrated the ability to determine the empirical formula of magnesium oxide. It also showcased the quantitative stoichiometric relationships between moles, mass, and molar mass in a chemical reaction. The balanced chemical equation for the combustion of magnesium was confirmed through the law of conservation of mass, where the total mass of reactants equaled the total mass of products.
The experiment highlighted the formation of an ionic bond between a metal (magnesium) and a non-metal (oxygen) to produce magnesium oxide. The empirical formula indicated the simplest ratio of elements in the compound, and it was found to be MgO, which aligns with theoretical expectations.
Three experimental errors that could affect the results include the potential escape of magnesium oxide fumes, incomplete combustion of magnesium, and inadequate firing of the crucible and lid. To improve results, consider the following:
In conclusion, this experiment successfully determined the empirical formula of magnesium oxide to be MgO through careful measurements, calculations, and the application of stoichiometry principles. The results align with theoretical expectations, and the experiment provided valuable insights into chemical reactions, stoichiometry, and the formation of ionic compounds.
Experiment Report: Determining the Empirical Formula of Magnesium Oxide. (2016, Mar 23). Retrieved from https://studymoose.com/document/magnesium-oxide-chemistry-report
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