Empirical_Formula

Empirical_Formula - CHM 1045L Empirical Formula Name:_ Lab...

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CHM 1045L Empirical Formula Name:_________________________________________ Lab Partner’s Name:_________________________________________ Date:________________________________ Empirical Formula Text Reference : Hill, et. al. 4e; Chapter 3 Lab Handbook Reference: Heating a Solid , pp 42-43 Discussion Many elements (both metal and nonmetal) combine with oxygen to form an oxide. Therefore, an oxide is a compound that contains oxygen and one other element. When magnesium is heated in a crucible, it reacts with oxygen to form a magnesium oxide. It also reacts with nitrogen to form magnesium nitride. In today’s experiment, the goal is to end up with only the oxide of magnesium. The nitride will also form, but in one of the steps, the addition of water and further heating will remove the nitrogen as ammonia and leave the hydroxide of magnesium. Further heating drives off the water, leaving the oxide. To determine the empirical formula of a compound, we perform a few calculations to obtain the subscripts of the formula. Throughout all calculations, be sure to keep significant figures. Failure to do so can give you a wrong answer. 1. Convert grams of each element to moles. Always use atomic masses. For example, even though nitrogen exists as a diatomic molecule, we would never use the molecular mass of nitrogen (28.02 g/mol), we would use only the atomic mass (14.01 g/ mol.) Think about the definition of an empirical formula: the smallest whole-number ratio of atoms in a formula. In order to determine this ratio, we must use atomic masses. 2. Divide each number of moles by the smallest number of moles. The answers to each of these calculations should be subscripts of the formula. If any of the answers to the calculations in this step end in 0.5, do not round this answer. Instead, you will need to multiply that answer and all of the others by 2 to obtain a whole number. If any of the answers to the calculations in this step end in 0.3, do not round this
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This note was uploaded on 04/26/2010 for the course CHM 1046 taught by Professor Musgrave during the Spring '09 term at Saint Petersburg.

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Empirical_Formula - CHM 1045L Empirical Formula Name:_ Lab...

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