Question

Use the following procedure for answering questions given below: 3.00 mL of 2.00 x 10' M solution of Fe(NO3)3 was mixed with 4.00 mL of 2.5 x 10-3 M solution of KSCN and 1.00 mL of 0.5M HNO3. After equilibrium: Fe3+ + SCN FeSCN2+ = was established the equilibrium concentration of FeSCN2+ ions was read from the calibration curve as 5.00 x 10-4 M. 01. The initial concentration of Fe3+ ions (assuming no reaction took place) was: [20] a) 1.00 x 10-3 M b) 4.20 x 10-4 M c) 7.50 x 10-4 M d) None 2. The initial concentration of SCN-ions (assuming no reaction took place) was: [20] a) 1.25 x 10-'M b) 4.50 x 10 4M c) 7.50 x 10-4 M d) None 3. The equilibrium concentration of Fe3+ ions was: [20] a) 1.00 x 10-4 M b) 2.50 x 10M d) None c) 3.60 x 10-5 M 4. The equilibrium concentration of SCN ions was: [20] a) 7.5 x 104M b) 6.00 x 10^ M M d) None c) 8.40 x 10-5 5. From the results found in questions 1-5 one can calculate that the equilibrium constant for the reaction is: [20] a 2.0 x 10-4 b) 8.40 x 103 M c) 2.7 x 103 M

Answer 1

J. Si = 2.00x103M V = 3 mL V = 3+ 4+1 8 mL 2 visi = V282 3 X 2.000103 7.5x10am. 32 . Ans -(e) 2. Vi 4 m2 si = 2.5x10-3 V2 = 8 m2 32 - ? vis, = S₂ V2 32 4 x 2.5 x 10-3 8 M 1.25x10 3M : Aus- (a) 4 3. [ FeSCN2t lear 5.00xio- м : [Fe 2+ Jeg = [Fe 2+] initial [Fe SCN 24 Jew 5x109) =(3-sXion 2.5x101 M :. (b) 4. 5 TECN-leq (SCN-Tinitial [FeSCN²Jew 1:25x10-3 7.5 x 15 am 58109 0 ie:.(a) MOCO 5. K = 5X10 4 (Fe s CN 2+1 [ Fe 2+] [sa] (2.5X109) (7.5x154 2.664 Xio! 3