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Determination of the Equilibrium Constant

Determination of the Equilibrium Constant. Theory. Beer’s Law : Concentration is proportional to Absorbance The reaction: Fe +3 + SCN - [Fe(SCN)] +2 Kc =. Beer’s Law : Concentration is proportional to Absorbance The reaction: Fe +3 + SCN - [Fe(SCN)] +2 K c =.

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Determination of the Equilibrium Constant

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  1. Determination of the Equilibrium Constant

  2. Theory • Beer’s Law: Concentration is proportional to Absorbance • The reaction: Fe+3 + SCN- [Fe(SCN)]+2 Kc = • Beer’s Law: Concentration is proportional to Absorbance • The reaction: Fe+3 + SCN- [Fe(SCN)]+2 Kc =

  3. Fe(SCN)+2 absorbs light in the blue-green region • Set up standard curve with absorbance readings for solutions of known concentration • Beer’s Law plot

  4. Math • Determine moles of each reactant species • Determine M for each based on total volume of solution • ICE • Keq = • Lab,P. 298

  5. Spectrophotometer • 3 clean cuvettes, wipes • Empty chamber • Light source on • Power knob: 0%T • Water blank • 447 nm • Clean cuvette with distilled water • Light source on • T knob: 100% T

  6. HNO3 blank • Set absorbance = to 0 • Test solutions • Zero the machine frequently • http://www.chm.davidson.edu/java/spec/spec.html

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