Chemistry TAS Report Essay

1. Experiment Number 10 2. Date 18/01/2008 3. Title end of the proportionality invariable for the reception Fe3+(aq) + SCN-(aq) FeSCN2+(aq) 4. Aims/Objective To determine the equilibrium constant for the reaction Fe3+(aq) + SCN-(aq) FeSCN2+(aq) 5. Introduction / Theory In this experiment, the equilibrium constant for the organisation of a complex ion, FeSCN2+(aq), is determined. Complex ions, thiocyanatoiron(III) ions, ar formed from iron(III) ions and thiocyanate ions in aqueous solution Fe3+(aq) + SCN-(aq) FeSCN2+(aq) (1).see morechemistry matriculation notes semester 1The equilibrium constant for this reaction isKc = FeSCN2+(aq) (2) Fe3+(aq)SCN-(aq) The product complex ion is the only star of the three species which has an appreciable color (blood-red). 6. Relevant Equations/Chemical Reactions Involved Fe3+(aq) + SCN-(aq) FeSCN2+(aq) 7. Chemicals 0. 002 M KSCN(aq) 50 cm3 0. 2 M Fe(NO3)3(aq) 20 cm3 8. Apparatus and equipment Boiling thermionic organ pipe 5 D ropper 2 10 cm3 measuring cylinder 1 Lamp 1 25 cm3 measuring cylinder 1 Wash store 1 Safety spectacle 1 250 cm3 beaker 1 9. Procedure 1. 0. 2 M Fe(NO3)3(aq) was used and 10 cm3 of 0. 08 M, 0. 032 M, 0. 0128 M, 0. 00512 M Fe(NO3)3(aq) were prepared respectively.The solutions were added by using 10 cm3 measuring cylinder to 5 clean boiling pipings in a rack as below. Tube No. 1 2 3 4 5 SCN-(aq) / cm3 10 10 10 10 10 Fe3+(aq) / cm3 10(0. 2 M) 10(0. 08 M) 10(0. 032 M) 10(0. 0128 M) 10(0. 00512 M) 3. Tubes 1 and 2 were wrapped around with a striptease of paper so that light was excluded from the side. 4. The solutions towards the lamp were looked vertically down to compare the distort intensity. 5. Some of the solution from the standard vacuum pipe 1 was removed with a dropper until the colouration intensities of solutions in both pipages were the same. And the removed liquid was stage into a clean and dry beaker.6. The depth of the solution in resistance 1 was then measured. 7 . Steps 3 to 6 were repeated with tubes 1 and 3, 1and 4 and finally 1and 5. 10. Observations The colour intensities of the solutions in the two tubes being sight were the same. 11. Data, Calculation and Results Height of solution in original tube 1 = 59 mm Height of solution in tube 1 having the same colour intensity as tubes 2, 3, 4 and 5 are Same colour intensity as 2 3 4 5 Height of solution in tube 1 (mm) 45 35 28 23 12. Conclusion The equilibrium constant for the reaction Fe3+(aq) + SCN-(aq) FeSCN2+(aq) was found to be 82.1 M-1. 13. Discussion 1. By M1V1 = M2V2, For tube 1, initial intentness of SCN-(aq) = 0. 001 M initial concentration of Fe3+(aq) = 0. 1 M For tube 2, initial concentration of SCN-(aq) = 0. 001 M initial concentration of Fe3+(aq) = 0. 04 M For tube 3, initial concentration of SCN-(aq) = 0. 001 M initial concentration of Fe3+(aq) = 0. 016 M For tube 4, initial concentration of SCN-(aq) = 0. 001 M initial concentration of Fe3+(aq) = 0. 0064 M For tube 5, initial concentration of SCN-(aq) = 0. 001 M initial concentration of Fe3+(aq) = 0. 00256 M 2. ingress of FeSCN2+ in tube 1 = 0.001 M 3. balance of depth in the colour comparison with tube 2 = 45 /59 = 0. 763 Ratio of depth in the colour comparison with tube 3 = 35 /59 = 0. 593 Ratio of depth in the colour comparison with tube 4 = 28 /59 = 0. 475 Ratio of depth in the colour comparison with tube 5 = 23 /59 = 0. 390 Equilibrium concentration of thiocyanoiron(III) ions In tube 2 = 0. 001 x (45 / 59) = 7. 63 x 10-4 M In tube 3 = 0. 001 x (35 / 59) = 5. 93 x 10-4 M In tube 4 = 0. 001 x (28 / 59) = 4. 75 x 10-4 M In tube 5 = 0. 001 x (23 / 59) = 3. 90 x 10-4 M 4. Fe3+equil = Fe3+initial FeSCN2+equil = 0. 04 7.63 x 10-4 = 0. 0392 M SCN-equil = SCN-initial FeSCN2+equil = 0. 001 -7. 63 x 10-4 = 2. 37 x 10-4 M 5. Room temperature = 16 oC K = FeSCN2+equil / (Fe3+equilSCN-equil) = 7. 63 x 10-4 / (0. 0392)(2. 37 x 10-4) = 82. 1 M-1 6. There are few sources of misunderstanding in this expe riment. (1) Determination of colour intensity in the two tubes observed big businessman not be accurate. (2) Taking reading when measuring the depth of liquid. fault estimation When taking initial reading, error is + 0. 05 cm3. When taking final reading, error is also + 0. 05 cm3. Therefore, error is + 0. 1 cm3.