Lab Titration

Topics: Concentration, PH, Mole Pages: 3 (905 words) Published: January 29, 2013
Determination of KC of Iron(III) Thiocyanato by Spectometry
Theory:
This study uses the method of measuring the equilibrium constant, Kc, for solution made of different initial reactant concentrations to determine the Kc for the reaction of iron(III)) and thiocyanato. The formula: Fe3+ +SCN- ⇔ FeSCN2+

The concentrations of the three substances at equilibrium will be determined by the stoichiometry of the reaction and the stoichiometric determination of the concentration of the complex AB. Beer's Law tells us that the absorbance, A, is proportional to the path length, l, and the molar concentration, c: A= e lc

The proportionality constant, , is called the molar extinction coefficient, e. For the spectrometer to be used, the path length, , is 1.00cm. At the wavelength of maximum absorption, the product of the path length and the molar extinction coefficient, has a value of 6120 L/mol for the iron-thianocyanato complex. Thus, if we start with known initial amounts of A and B, and know the concentration of AB at equilibrium, the we can calculate the the amount of A and B at equilibrium. There are centain ranges of wavelength that will be absorbed by the object, while it will transmit other wavelength. The reason why an object has a particular color is because it can only absorb specific wavelenghts and transmit others. Spectrometer is used to measure concentration because the amount of light absorbed by a solution is proportional to its concentration at a constant wavelength; the higher the concentration of solute, the more light will be absorbed and a higher reading will be obtained on the spectrometer.

Procedure:
Part A:
1. Obtain 10.0 ml measuring (MoHr) pipet and two cuvettes from a storeroom. 2.Pipet 7.0ml of 0.5M HNO3 into blank cuvette.
3.Into other pipet 4.00 mL of A and 3.00mL of B
4. Cover mouth of pipet w/plastic wrap place thumb on top of plastic and carefully shake. 5. Before placing cuvette into compartment wipe with chem tissue....