Question

The reaction of cobalt(II) nitrate and potassium thiocyanate produces a coloured complex, [Co(SCN)4]2-(aq). The initial concentrations of the reactants after mixing (before any reaction) were 0.250 mol/L Co(NO3)2(aq) and 0.500 mol/L KSCN (aq). After 20 minutes, the absorbance of the solution was 0.825. The complex, [Co(SCN)4]2-, is the only absorbing species (ε b = 9.29 (mol/L)-1). Determine the concentration of Co2+ at equilibrium.

The reaction of cobalt(II) nitrate and potassium thiocyanate produces a coloured complex, Co(SCN).J(aq). The initial concentrations of the reactants after mixing (before any reaction) were 0.250 mol/L CO(NO),(aq) and 0.500 mol/L KSCN (aq). After 20 minutes, the absorbance of the solution was 0.825. The complex, [Co(SCN).]”, is the only absorbing species (€ b = 9.29 (mol/L)'). Determine the concentration of Coat equilibrium. O 1.44 x 10-'mol/L 4.06 x 10 mol/L 9.29 x 10 mol/L O 1.61 10 mol/L 7.32 x 10 mol/L

Answer 1

The reaction CO(NO3), (09) + 4 kschlag) = K[C(SCN)4] (09) +2KNO; t=0 0.250 moll 0.500 mol/L 0 we know AzEEL where c where c is the concent & 0825-cxeb ration of absorbing se cies tore its 2 0.8752 Cx9.29 [Co (SCN) 472- 2 C=0.0888mol/L A = absorbance So, the concentration of [co (SCN) 4] 2 is 0.0888 mohet Then at aquen the concentration of colNO3)2 is (0.250 0.0988) mellit - 0.161 mol/L 1061x 101 mol/lit The only on tosowice of coat in the solution is Co (NO2), (aa). So, the concentration of Co2t is 1.618 15' mollit