Chem 2080 prelab 3 - 3+ ] minus the equilibrium [FeSCN 2+...

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-1 EXPERIMENT 3 Spectroscopic Determination of an Equilibrium Constant The answers to these questions are due at the beginning of lab the week of 3/1 – 3/5/10. Pre-laboratory Questions: 1.) Calculate the initial concentrations of Fe 3+ and SCN for the six solutions to be prepared in this experiment (the solutions prepared in test tubes 1–6). These are the concentrations just after the two solutions are mixed in the large test tube (thereby diluting each other) but before any FeNCS 2+ has formed. Assume that the volumes are additive and that the Fe(NO 3 ) 3 and KSCN are each completely dissociated. Report your answers using the table format shown below Test tube Initial [Fe 3+ ] Initial [SCN ]
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2.) If the equilibrium [FeSCN 2+ ] in test tube 2 was determined to be 9.5 × 10 –5 M, calculate the equilibrium [Fe 3+ ]. (The equilibrium [Fe 3+ ] is equal to the initial [Fe
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Unformatted text preview: 3+ ] minus the equilibrium [FeSCN 2+ ]. This follows from the stoichiometry of the reaction.) 3.) If the equilibrium [FeSCN 2+ ] in test tube 2 was determined to be 9.5 10 5 M, calculate the equilibrium [SCN ]. 4.) For the solution in test tube 1 why can you assume that the equilibrium concentration of FeSCN 2+ is equal to the initial concentration of SCN in the test tube? 5.) Why must the test tubes be completely dry before use? 6.) Why is it important to rinse the cuvet several times with the solution to be analyzed before filling it to measure the absorbance? 7.) Why must all the absorbance measurements be made at the same wavelength? 8.) Write in your lab notebook the following modification to the Lab Manuals procedure: Waste Disposal (page 13): All chemical waste generated in this experiment may be poured down the sink....
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This note was uploaded on 03/31/2010 for the course POLITICAL 101 taught by Professor Han during the Spring '10 term at Hong Kong Shue Yan.

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Chem 2080 prelab 3 - 3+ ] minus the equilibrium [FeSCN 2+...

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