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Creating The Unknown Concentration Of Cu + 2

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Creating Solutions of Standard Molarity
Madelene Andersson
Sarah Toadvine
CHEM 1251L-013
10/13/2014

Introduction: The purpose of this lab is to find the unknown concentration of Cu+2 by comparing the solution to a set of standard concentrations, different known concentrations, which are prepared by diluting approximately 2.5 grams of copper (II) sulfate pentahydrate. A concentration is the amount of solute relative to the volume of a solution, the more solute the more concentrated the solution will be. Concentrations are reported using molarity (M) which is the moles of the solute by the volume of solution in liters. A spectrophotometer called the Spec 20 and the Beer-Lambert law is used to determine the concentrations of solutions. The Spec 20 is used to measure the amount of light that passes through a solution. This is measured in terms of absorbance which is the amount of light a solution absorbs or transmittance which is the amount of light that passes through a solution. The relationship between absorbance and transmittance is A= -log T or A=2-log (%T).
The Beer-Lambert Law establishes the quantitative relationship between absorbance and a solution’s concentration.
The formula is A=ԑbc
A=absorbance
ԑ=molar absorptivity constant b=the path length (cm) through which light travels c=molar concentration of solution
The Beer-Lambert plot (absorbance vs. concentration) establishes a calibration curve that is used to determine the concentration of a solution of the same

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