Question

a) First, you obtain a test tube and fill it with 2 ml of 0.25 M CoCl2. You add 12 M HCl until the solution turns purple.

1. How did the addition of 12 M HCl affect the equilibrium?

2. How did the relative concentrations of Co(OH2)62+ and CoCl42- change after the addition of 12 M HCl? Justify your answer based on the previous step.

b) Next, you obtain another test tube with 2 ml of 0.25 M CoCl2 and you add 0.1 M AgNO3 until the solution turns pink.

1. Is the equilibrium affected by the addition of 0.1 M AgNO3?

2. How did the relative concentrations of Co(OH2)62+ and CoCl42- change after the addition of 0.1 M AgNO3? Justify your answer based on the previous step.

Answer 1

A.

Formation of hexaaquaCobalt(II) and TetrachloroCobalt(II) complexes takes place which in turns show colour as they are paramagnetic in nature. As the consumption of CoCl2 is increasing, the equilibrium shift backward direction to attain a new equilibrium.

B.

Since AgNO₃ forms precipitation with chloride ions, so the relatively the concentration of Co(OH2)₆²⁺ is higher than CoCl₄^2-