Empirical formula of magnesium oxide
Abstract:
The goal of this experiment was to calculate the empirical formula of magnesium oxide by reacting magnesium with atmospheric oxygen. The smallest whole number ration of moles of magnesium to moles of oxygen in magnesium oxide will determine the empirical formula. Before the experiment began, safety procedures were reviewed. The materials that we used were general lab tools and the chemicals.
The first step was to record the mass of magnesium used as the reactant and the mass of magnesium oxide product. Then we began to heat the magnesium until it began to emit light. Then a cover was placed on it and it was cooled. This was repeated multiple times. Once all of the magnesium was reacted, the mass of the crucible and magnesium was recorded. Once that was finished, we calculated the mole of magnesium and oxygen. In addition, we calculated the mass of each substance formed. With the results collected and data calculated, the empirical formula of magnesium oxide was found to be MgO.
Introduction:
This experiment was made possible by Antoine Lavoisier in the latter half of the 18th century. He performed many combustion experiments and observed the different results. He then summarized his work in the law of conservation of mass. This states that the mass of the reactants will be equal to the products. Matter is neither created nor destroyed in a reaction. In this experiment finding the empirical formula of magnesium oxide will be the main goal of this experiment. The empirical formula is different than the molecular formula which is the actual number of atoms of each element in the substance. The empirical formula is the simplest, whole number ration of atoms in that formula. The hypothesis of the experiment was that the empirical formula will be MgO since Mg has a 2+ charge and O has a 2- charge. The experiment will have magnesium react with oxygen to form magnesium oxide.
Materials and Methods: The materials that were need for this experiment include the following:
• Magnesium
• Crucible with lid
• Clay triangle
• Iron ring and stand
• Crucible Tongs
• Bunsen burner w/ matches
The first step in the experiment was to clean the crucible and make sure there were no cracks in it. The crucible was cleaned by firing for 3-5 minutes and then letting it cool. As the crucible was cooling, about 0.3 g of magnesium was obtained and the actual mass was recorded. The magnesium was then coiled into a tight spiral and placed in the bottom of the crucible after the mass of the crucible was recorded. Then their combined mass was found. The crucible was then placed on the clay triangle connected to the iron ring and stand. The crucible lid was set ajar so atmospheric oxygen could react with the magnesium. The Bunsen burner was then started and the crucible began to be heated. Once there was a flash of light from the magnesium, the crucible lid was put completely on and the flame was removed. The lights were turned off so the flashes of light were visible.
After the initial flashes of light, the crucible was cooled for 2-3 minutes until heating again. The process of heating, waiting for the flashes and the cooling were repeated until there were no long light flashes and all of the magnesium was reacted.
Up to now, we have assumed the unbalance equation is this Mg(s) + O2(g) → MgxOy(s). However, some of the magnesium has reacted with atmospheric nitrogen at such high temperatures. The equation for this reaction is 3Mg(s) + N2(g) → Mg3N2(s), however Mg3N2 can be converted Mg(OH)2 by the addition of water and heat. The balanced equation for this reaction is Mg3N2(s) + 6H2O(l) → 3Mg(OH)2(s) + 2NH3(g). Then we can convert the magnesium hydroxide to magnesium oxide by