Question

Purnula Bf Coll) complex ion present in solution in a. 12 M HCI b. diluted solution colto- c. hot solution t o lesbian OHI DOO d. cooled solution Tebwinobs b ing Explain the color change that occurred when stor odi o a. water was added in Step 2. (Consider how a change in [CI-] and [HO] will shift Reaction 7.) b. the diluted solution was heated. (How would Reaction 7 shift if K. went up? How did increasing the temperature affect the value of K ? What is the sign of AH in Reaction 7?) temper (continued on following page)

Answer 1

Co(H₂O)₆²⁺(aq) + 4 Cl^-(aq) $\leftrightharpoons$ CoCl₄^2-(aq) + 6 H₂O(l). ∆H > 0

Pink color. Blue color.

Formula of Co²⁺ ion present in solution

(a) 12 M HCl. CoCl₄^2-

(b) diluted solution. Co(H₂O)₆²⁺

(c) hot solution. CoCl₄^2-

(d) cooled solution. Co(H₂O)₆²⁺

Color change :

(a) when water is added to the Co²⁺ solution , the above equilibrium would shift backward (or towards left ) and color of solution becomes pink .

(b) when diluted solution is heated the color of solution becomes blue . The above reaction is endothermic in nature . As the temperature is inceased , the value of K_c increases and concentration of chloride complex is more . Hence blue color.

∆H >0 (i.e. positive ) .