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Empirical Formula Lab

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Determining the Empirical Formula of Magnesium Oxide Lab Report

Observation and Results

Mass (g)
Mass of clean, empty crucible and lid
54.3464 g
Mass of crucible, lid and magnesium
54.3919 g
Mass of crucible, lid and magnesium oxide
54.4093 g
Table 1: Experimental Masses of Equipment, Reactants and Products
Masses of relevant equipment, reactants and products were recorded to be used later in calculations to determine the percent composition and empirical formula of magnesium oxide.
Mass of magnesium
0.04550g
Mass of oxygen
0.01740g
Mass of Magnesium Oxide
0.06290g
Experimental - Percent Composition of Magnesium
72.3370%
Experimental - Percent Composition of Oxygen
27.6630%
Moles of Magnesium
0.001871657 moles
Moles of Oxygen
0.0010875 …show more content…

It was determined by using the mass of the products divided by the mass of the product, then multiplied by 100% to get the value in a percent. The percent composition of the product concluded to there being approximately 72.3370% magnesium elements and 27.6630% oxygen elements in the compound. Percent composition shows the mass percent of an element in a compound in relation to the other elements. Then calculating number of moles and dividing each mole by the smallest from the two, created the subscript of the experimental empirical formula. The experimental empirical formula resulted to be Mg3O2. Empirical formula is derived from experimental observation, not theory. It expresses the simplest ratio that the elements are combined in however, it is not necessarily correct information about the number of atoms in a molecule and does not express the quantity of atoms in the sample. The ratio of magnesium cations to oxygen anions is 3:2. The theoretical empirical formula is MgO. This formula shows the number of elements expected to be in the compound and the simplest ratio of the elements in the compound. This is determined because this is a synthesis reaction of magnesium and oxygen. Magnesium has a 2+ charge while oxygen has a 2- charge, when the charges are crossed, it creates the compound, MgO. To calculate the mass percent or theoretical percent composition, …show more content…

This created a distance from the hot surface of the crucible from the Bunsen burner thus, not allowing the experiment to conduct. With the magnesium not touching the hot surface, there is a lack of energy for the chemical reaction to happen and not produce magnesium oxide. Another possible experimental error is that when crushing the magnesium oxide to a fine powder with a glass rod, water was used to wash off the magnesium oxide on the rod to get a more accurate mass. However, due to the solution being hot from the Bunsen burner, adding water created evaporation and also resulted in the solution to spill on to the lab bench which affected the mass and calculations. Also, connecting to this experimental error could be that the glass rod was not washed properly with the distilled water leaving some of the fine powder thus, leading to an approximate mass rather than an exact mass. The solution that was produced was not a 100% magnesium oxide as the magnesium strip was reacting to the air and the air does not have 100% oxygen atoms only. Another error for this experiment could be the unequal supply of oxygen. For this experiment to be more successful, there should be excess amount of oxygen entering the magnesium strip. Another ways to make the lab better is by following the procedure and keeping full attention to minor detail

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