em1.png ... Part 3: Q Average absorbance Flask & 1:1 Ratio so Flash D Flask 10 Flask 11 Part 3 Q Flask 8 Flask 9 Flask 10 Flask 11 Part 3: Q10 Flask 8 Flask 9 Flask 10 Flask 11 0.146 0.166 0.215 0.294 (FESCHXmol/L) 4.59-10 5.18-10 6.64-10 9.08-10 [FXmol/L) 5.00-10 5.00*10* 5.00*10* 5.00*10* Y=3362x-0.0083 0.9993 Part 3 (Amounts of flask 8(9-11's values are in the spreadsheet) 71% [Fe] -0.002mol/L volume = 5.00ml Molarity of Fe(NO3)3 = 0.2M Volume of Fe(NO3))3= 5.00mL Moles of Fe¹ = Molarity x volume(1) Moles of Fe¹ = 0.2M x 0.0051 = 1×10-³mole [SCN mel/ 4x104 5x108 7.10 1.10 Concentration of Fe=0.002M 1 8. Average absorbance for solution 8 (same for 9-11) Average absorbance for flask 8= sum of all absorbances / number of readings (0.145 +0.147 +0.148) 3 Using equation of calibration curve's line(slope) of best fit, the average absorbances of the unknown concentrations to determine [FeSCN-Jat equilibrium in solution 8: quation of line Y=3362x-0.0083 For 8 with an average absorbance of 0.146 9. X= 10, [Fe] = = 0.146 0.146 3362X-0.0083 (0.146 +0.0083) 3362 = 4.59 x 10 25mlFe³ x 0.002mol/l-1 100ml 5.00 x 10 mol/l- 11. Place the results from calculations 9 and 10 into individual ICE tables. Calculate the equilibrium concentration of Fel and SCN-in solutions 8 to 11 TABLE 2-COMPOSITION OF SOLUTIONS REQUIRED FOR CALCULATION OF EQUILIBRIUM CONSTANT Volume of 0.002 mol L Volume of 0.002 mol L-³ Flask # Fe(NO3)(aq) /ml. KSCN[an) / mk. 7 (bank) 8 9 0.00 20.00 25.00 50.00 Ensure your Thermo Scientific Spectronic 200 spectrophotometer is powered on so that it is warmed up by the time you use it later in the procedure. Pipette 5.00 mL of 0.2 mol L4 Fe(NO)(aq) into a clean 500-ml volumetric flask. Fill the flask carefully to the calibration mark with 1.0 mol L HNO(aq), stopper it, and mix well by inversion (25 times). Pour about 175 mL of the solution you just prepared into a clean, dry 250-ml beaker. The concentration of Fe(NO)(aq) in this solution is approximately 0.002 mol L-4 Pipette the required volumes of 0.002 mol L Fe(NO)(aq) and then 0.002 mol L KSCN(aq) into five clean. labelled 100-ml volumetric flasks. Before using the 25-ml pipette to deliver KSCN(aq) solution, remember to rinse it with this solution three times to remove any traces of Fe(NO)(aq) that might be in it. Fill the flasks precisely to the calibration marks with delonized water. Remove any water droplets above the marks with a Kimwipe. Stopper the flask and mix each thoroughly by inverting it 25 times. Measure the absorbance of the solutions in flasks & through 11 as outlined in part 3 of the procedure. 10 11 5.png 25.00 25.00 25.00 25.00 25.00 35.00 Q61% Fe³" (aq) + SCN" (aq) un FeSCN³(aq) The equilibrium constant K, is a ratio of the product of the the products to that of the tions of reactants, with the concentrations raised to the power of their stoichiometric coefficients. So, for the reaction under consideration King In Part 1. solutions will be prepared with known concentrations of FeSCN, a coloured species that can absorb light of a particular wavelength. The portion of incident light absorbed-called the absorbance-can be determined using an instrument called a spectrophotometer. The absorbance of the solutions will be plotted against (FeSCN resulting in a graph known as a calibration curve (even though the data is linear). By performing a linear regression analysis. It can be determined if the data conforms to Beer's Law. This law is used in spectroscopy to determine concentrations of species in solution. It can be expressed as Awabe where is the absorbancer is the molar absorptivity of the absorbing species. b is the length of solution through which the light passes (also called the path length), and is the concentration of the absorbing species. In Part 2. the absorbance of solutions with unknown concentrations of FSCN will be measured. Using these measurements and the equation of the calibration curve line the equilibrium concentration of FeSCN³(aq) in each solution can be determined. ICE tables are then used to find the equilibrium concentrations of all species present in Equation (2) and the equilibrium constant for Reaction (1) will be determined