Determination of Equilibrium Constant, Keg several dilutions of stock solution a

Question

Determination of Equilibrium Constant, Keg several dilutions of stock solution and use the dilution formula to determine (%T) and convert correctly to 2. Calibrate a spectrophotometer and record percent transmittance 6 3. Create a calibratio a absorption. bsorptionlUing the equation of the best fit line of the calibration data and product to determine the equilibrium constant for the reaction. average equilibrium constant with initial concentration data. n curve by plotting absorption values vs known concentrations for the complex, Fe(SCN)2 n solutions to determine their concentrations. 4. Create an ICE table from initial concentrations of reactants and equilibrium conceh n concentration of 5. Demonstrate your ability to use the quadratic formula in a sample calculation using the Many chemical reactions are shown as procceding from reactants to products completely The reactions are written such that a single headed arrow points to the right toward all products indicating that no reactants are left following the reaction and the reaction is not easily reversed In the aftermath of a combustion reaction (Equation 1) the products, CO; and H:0, are to break apart and reform the starting materials as indicated by the single-headed arrow. unlikely 2 CHL(g) + 70;(g) 4 CO2(g) + 6H20(g) Eq. 1 However, some reactions proceed to a point of equilibrium. After a certain amount of products have formed, the products begin to react with one another, reforming the starting materials. When quantities of product are reacting in the reverse direction as fast as the reactants are forming products, the system is said to be in equilibrium. The state of equilibrium is denoted with a set of double arrows, one pointing to the right and one to the left (Equations 2) The specific reaction that we will be studying in the lab is the reaction of the iron(I) cation (Fe) complexing with a thiocyanate anion (SCN to form an intensely red product, the iron(III) thiocyanate complex, Fe(SCN) (Equations 2a,b,c). Note that Equation 2c is written as the net ionic equation and that the molecular and total ionic equations are seen in Equations 2a and 2b, respectively Fe(NO3)3(aq)+ KSCN(aq) [Fe(SCN)](NO)2(aq) KNO3(aq) + Eq. 2a Eq. 2b Eq. 2c Fe"(aq) + SCN (ag) Fe(SCN)'.(aq) If a system is at equilibrium and the rate of formation of products is the same as the rate of reformation of reactants, then the concentration of each species is not changing. Therefore an expression denoting the rates of forward and reverse reaction is set equal to an equilibrium constant, Ko Ke is equal to the multiplicative product of the concentrations of the products raised to the powers of their coefficients divided by the multiplicative product of the concentrations of the reactants raised to the powers of their coefficients. Equation 4 represents

Explanation / Answer

PLOT A GRAPH OF ASORBANCE V/S Concentration of Fe(SCN)2+ formed
Slope gives value for Concentration of product at equilibrium

To find Concentraion of Fe(SCN)2+
Molarity of KSCN x Volume of KSCN = Molarity of Final solutionx Total volume

ex. 0.002x0.5 = Mx X 20 ml

MX= 0.5 x 10-4 M

Plot graph of Final concentration v/s asorbance

slope(m)= 1514= [Fe(SCN)2+]= 1/1514= 0.00066=Y moles at equilibrium

For Final Molarity of Product

K= Equilibrium constant= Product/ Reactants

0.00066/ 0.1993x0.00134

= 2.2479

Use the value pf K to determine concentraion of Equilibrium product in the last table

Sr No Volume of KSCN Final Concentration of Fe(SCN)2+ (M) 1 0.5 0.5 X 10-4 2 1.0 1.0X 10-4 3 1.5 1.5 X 10-4 4 2.0 2.0 X 10-4 5 2.5 2.5 X 10-4

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