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Formal lab2 - Determination of the Stoichiometry for Redox...

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Determination of the Stoichiometry for Redox Reactions CHE 120-03 Instructor: Lesley March 9, 2008 Purpose
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In this exercise you will perform redox reactions between metals (Mg, Al, and Ca) and hydrochloric acid or water to determine the stoichiometric coefficients (whole numbers) of the balanced chemical equations based on the moles of metal used and the moles of hydrogen gas produced. Introduction The redox reaction in this experiment between metals and hydrochloric acid produces the corresponding metal chloride salt and hydrogen gas. This type of reaction differs from a metathesis reaction based on the change in oxidation states of the atoms during the reaction. The term redox is in reference to the changes the electrons of the compounds undergo during the reaction. In a redox reaction one side gains electrons and the other loses, so you have a reduction and an oxidation. Each group is to do six experiments with varying masses of metal. All the data is to be tabulated and graphs made. The slope of the Mg vs. H2 graph will be the stoichiometric equivalent for the moles of metal in relation to the moles of h2 gas for experiments with Al and Ca. The point of this lab is to show the importance of the mole and of stoichiometric equivalents in correlation with balanced chemical equations. The mole is the link between the world of atoms and molecules with the world of large mass measurements (112). Using the mole measurement one can relate and determine the amount of one element embedded in another. The key to these equations is the stoichiometric values present. This experiment uses known moles of metals to determine the stoichiometric equivalent of hydrogen gas by using graphs. The slope of the Magnesium vs. Hydrogen gas (mL) is the conversion factor needed to find moles of hydrogen gas from the volume of hydrogen gas. The moles of H2 gas is found by dividing the volume of H2 gas by the slope of the Mg vs. H2 (mL) graph. Using the volume of hydrogen gas that was determined by experimentation the moles of hydrogen gas can be attained. Making a graph of moles metal vs. moles H2 and finding the slope of the fit line is how the stoichiometric values of the balanced equations are derived. The slope of this new graph is the stoichiometric value of
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