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Chem 2080 Lab report exp 5

# Chem 2080 Lab report exp 5 - Preparing a Buffer Solution By...

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Preparing a Buffer Solution By Molly McMahon Lab Instructor: Megan Kopp March 19, 2010 Desk A

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Purpose A buffer solution with a certain pH and approximate volume of 400mL was prepared. This buffer had the capacity to absorb 20 mL of either .02M HCL or .02 NaOH, and underwent a pH change of no more than + or - 0.1. Materials and Equipment Ÿ 400 mL of C 3 H 4 N 2 Ÿ 25 mL of .02M HCL or .02M NaOH (in some trials NaOH was used, which raised pH; and in others, HCl was used, which lowered pH) Ÿ Beaker for mixing solution Ÿ PH meter Ÿ Balance to weigh out C 3 H 5 N 2 Cl (according to calculations, .753g of C 3 H 5 N 2 Cl would be the ideal amount to change our pH by no more than .1) Calculations K a = 1.0 x 10 -14 = 1.11 x 10 -7 9.0 x 10 -8 6.7= -log(1.11 x 10 -7 ) + log( [C 3 H 4 N 2 ] / [C 3 H 5 N 2 Cl ] ) 6.7= 6.95 + log( [C 3 H 4 N 2 ] / [C 3 H 5 N 2 Cl ] ) 6.7-6.95= log( [C 3 H 4 N 2 ] / [C 3 H 5 N 2 Cl ] ) -.25= log( [C 3 H 4 N 2 ] / [C 3 H 5 N 2 Cl ] ) 10 -.25 = ( [C 3 H 4 N 2 ] / [C 3 H 5 N 2 Cl ] ) .562= .01/ [C 3 H 5 N 2 Cl ] [C 3 H 5 N 2 Cl ] = .01/.562 = .018 M _______________________________________________________________________ .018 mol x 104.543 g = 1.889 g x .4L = .753g C 3 H 5 N 2 Cl 1 L 1 mol 1 L
Data and Results Trial 1 2 3 4 5

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