# Procedure part i preparing standard solutions for

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Procedure Part I: Preparing Standard Solutions for FeNCS 2+ ion Beer’s Law Plot Label five 50-mL volumetric flasks B-F. Add the amount of 0.200 M Fe(NO 3 ) 3 and 0.002 M KSCN to each of the labeled flasks as indicated in the table below. Add enough 0.1 M HNO 3 to each flask to bring the total volume to 50.00 mL. Thoroughly mix each solution. Solution 0.200 M Fe(N0 3 ) 3 , mL 0.002 M KSCN, mL *M SCN - **M FeNCS 2+ A(blank) 0.00 0.00 0 0 B 10.00 1.00 4.00 x 10 -5 .04 C 10.00 2.00 8.00 x 10 -5 .04 D 10.00 3.00 1.2 x 10 -4 .04 E 10.00 4.00 1.6 x 10 -4 .04 F 10.00 5.00 2.00 x 10 -4 .04 * Calculate the molar concentration of SCN - in each solution: ) 4 ( , ) )( ( ) ( equation ml volume total solution KSCN M KSCN ml SCN M ** M FeNCS 2+ is the same as calculated M SCN - . Page 3 of 6
323b2c945a63e0e482c75268aa4221182a6c51fc.docx Part II: Preparation of Equilibrium Mixtures Label five 50-ml volumetric flasks 1-5. Add the amount of 0.002 M Fe(NO 3 ) 3 and 0.002 M KSCN to each of the labeled flasks as indicated in the table below. Add enough 0.1 M HNO 3 to each flask to bring the total volume to 50.00 mL. Thoroughly mix each solution. Eq. Mixture 0.002 M Fe(NO 3 ) 3 , mL *M Fe 3+ (initial) (use Eq. 5) 0.002 M KSCN, mL M SCN - (initial)  (use Eq. 4) 1 25.00 5.00 2 25.00 10.00 3 25.00 15.00 4 25.00 20.00 5 25.00 25.00 *Calculate the initial molar concentration of Fe 3+ : ) 5 ( , ) ) ( )( ( ) ( 3 3 3 3 equation ml volume total solution NO Fe M Fe ml Fe M Reading Equilibrium Mixtures with the Colorimeter Click on Read Unknowns. Rinse cuvette with the unknown sample to be read. Click on Add. Sample ID: Enter number of sample. Click OK. Read Equilibrium Mixtures 1-5 and record concentration in the table below. Eq. Mixture [FeNCS 2+ ] (eq) (from Beer’s Law Plot) 1 Page 4 of 6
323b2c945a63e0e482c75268aa4221182a6c51fc.docx 2 3 4 5 Calculate [Fe 3+ ] (eq) and [SCN - ] (eq) and record in the table. Calculate K c for each equilibrium mixture (Equation 1). Eq. Mi x [Fe 3+ ] (eq) = (Eq. 2) [Fe 3+ ] (i) – [FeNCS 2+ ] (eq) [SCN - ] (eq) = (Eq. 3) [SCN - ] (i) – [FeNCS 2+ ] (eq) K c 1 2 3 4 5 Average K c = ___ Print graph and scan it. Turn it via email along with the datasheet. Graph should have a title and the axes must have units and be labeled. The title should be descriptive, dated and include the student names.
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