Question

Data and Calculations: Determination of the Equilibrium Constant for a Chemical Reaction Method II Volume in mL 2.00 x 103 M Fe(NO) Volume in mL, Depth in mm Volume in ml. 2.00 x 103 M Method I Mixture Unknówn KSCN Water Absorbance Standard FESCNP 4mL 1 5.00 x 10 M 1,00 .227 3mL 2 5,00 202 x 10 M 2,00 90 x 10 M .304 3 5,00 3.00 2mL 955 x 104 M I ImL 4 5.00 4,00 19x 10 M O mL 5 5.00 5.00 If Method II was used, [FeSCN].mndand 10-1 M; [FeSCN21 in Mixtures 1 to 5 is found by Equation 7. Processing the Data Fe (aq) +SCN (aq) FeSCN2 (aq) (1) Calculation of K, assuming the reaction: A. This calculation is most easily done by following Steps 1 through 5 in the discussion. Results are to be entered in the table on the following page. If you are using Excel, set up the table as we have, and follow the directions that follow. and SCN in the mixtures in test tubes 1 through 5. Usc Equation 3 and enter the values in the first two columns of Step 1 Find the initial number of moles of Fe the table. Step 2 Enter the experimentally determined value of [FeSCN2 at equilibrium for each of the mixtures in the next to last column in the table. Use Fquation 3 to find the number of moles of FeSCN2 in each of the mixtures, and enter the values in the fifth column of the table. Note that this is also the number of moles of Fe+ and SCN that were used up in the reaction. (continued on following page) 4 Step 3 From the number of moles of Fe and SCN- initially present in each mixture, and the number of moles of Fe and SCN used up in forming FeSCN2, cal- culate the number of moles of Fet and SCN that remain in each mixture at equilibrium. Use Equation 4. Enter the results in columns 3 and 4 of the table. Step Use Equation 3 and the results of Step 3 to find the concentrations of all of the species at equilibrium. The volume of the mixture is 10.00 mL, or 0.0100 liter in all cases. Enter the values in columns 6 and 7 of the table. Step 5 Calculate K, for the reaction for each of the mixtures by substituting values for the equilibrium concentrations of Fe, SCN-, and FeSCN2+ in Equation 2. Step 6 Calculate the mean value for K, and the standard deviation. (See Appendix VIII.) Ceoncentrohorx 10 Mixture Initial No. Moles Equilibrium No. Moles Equilibrium Concentrations K. SCN [FeSCN2 Fe Fe SCN FeSCN2+ Fe] ISCN x 10- M 227 x10- x 10-6 x 10- M x 10- x 10% x 10 M 10- 46 x10-0 0940x10-0 ,955X10- 4 119X10-6 5 noveus tu Mean value of K_ Standard deviation (continued on following page)

Answer 1

Tithial No. msles Equisbaum Cenenbehion. Mixture Equilibaium na Ma le fesca Cres SCNO fe3r Sce CDPe 9.773 -773 31 .223x1 9.723 X 773 0 23 99IKO1 2x10 9 5yx10 3.54 L36X103 4X109 9.54%63.5R 10XI6 .30x1 .31 1416 9oy SY1E 7.05Xio o955x15 1ox1g 4 &8ixig 5. Jox10 Mean Valu af k 142x102 A Molarty avolome (m) Trh al No )oou Dmihial moles Equeilibim maler of fe Nes Equilibriun Na & mole al fest Sco Eqwiibrium me les x1op Equilibrivm Ceeahahem Cfe3J seNo