Lab4A_Chemical Formula

Lab4A_Chemical Formula - CHE 1315. General Chemistry I...

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CHE 1315. General Chemistry I Experiment#4A The Determination of a Chemical Formula John Dalton was an Englishman, a teacher, and an exceptional theoretical chemist. He developed and wrote the modern atomic theory at the turn of the 19 th century (documents point to 1803). He was influenced by the experiments of two Frenchmen, Antoine Lavoisier and Joseph Louis Proust. A fundamental component of the modern atomic theory is that the mole ratios of elements in a compound will be small whole numbers ( law of definite proportions ). The whole number mole ratio is commonly referred to as the empirical formula of a compound. One of the challenges in finding the proper chemical formula for a compound is that there may be more than one plausible mole ratio for the elements in that compound. Dalton called this the law of multiple proportions . For example, if you were testing a compound that contained iron and sulfur, the plausible chemical formula could be FeS or Fe 2 S 3 . However, if you determine the mass of iron and the mass of sulfur present in a given mass of the compound, you will be able to establish the true chemical formula of the compound. In this experiment, you will use the law of definite proportions to find the chemical formula for a hydrated compound containing copper, chlorine, and water molecules locked in the crystal structure of the solid compound. The general formula for the compound is Cu x Cl y zH 2 O, and its name is copper chloride hydrate. The letters x, y, and z represent integers that will establish the proper chemical formula for this substance. First, you will gently heat a sample of the compound to drive off the water of hydration. By measuring the mass of the sample before and after heating you can determine the amount of water in the sample and identify the value of z. Second, you will conduct a chemical reaction with the dried sample, which will produce elemental copper. By measuring the mass of copper that forms, you will have the necessary information to determine the moles of copper and chlorine in your sample, and you will be able to establish the proper chemical formula. OBJECTIVES In this experiment, you will Determine the water of hydration in a copper chloride hydrate sample. Conduct a reaction between a solution of copper chloride and solid aluminum. Use the results of the reaction to determine the mass and moles of Cu and Cl in the reaction.
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This note was uploaded on 01/30/2011 for the course CHEM 1265 taught by Professor Deeter,g during the Spring '09 term at Tulsa Community College.

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Lab4A_Chemical Formula - CHE 1315. General Chemistry I...

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