1. CoCl,\'(aq) (blue) + 6 H,O(1) Co(H,Oh!\"(aq) (pink) + 4 Cl-(aq) Reagents: 0.1

Question

1. CoCl,'(aq) (blue) + 6 H,O(1) Co(H,Oh!"(aq) (pink) + 4 Cl-(aq) Reagents: 0.1 M CoCl2 in 95% ethanol (Measure 3 mL into a clean, dry test tube) Caution: CoCl, in ethanol is flammable, toxic and irritating 12 M hydrochloric acid, use drop wise (Caution: Use in the hood with gloves!) deionized water, use drop-wise Prepare the equilibrium by adding deionized water, 1 drop at a time and mixing well after each drop, to 3 mL of the CoCl, solution until the solution turns a light purple color. a. Equilibrium concentrations in equation (1) are shifted left by adding: HC D) Observation: tvrned a blvish pur ple ii) Net-ionic equation: b. Equilibrium concentrations in equation (1) are shifted back to the right by adding H20 i) Observation: Pink Net-ionic equation: ii)

Explanation / Answer

a)

While adding 12 M HCl, (CoCl2.2H2O) reacts with Cl- to produce CoCl42-(blue in colour).Since Cl- is excess in solution,Co2+ tends to react/co-ordinate with chloride rather than H2O.The net ionic eqation is given below-

Co(H2O)62+(aq) (pink) + 4 Cl-(aq) <--> CoCl42-(aq) (blue) + 6 H2O(l)

b)

When excess of H2O is added, the concentration of Cl- is diluted and H2O can again co-ordinate with Co2+ to form [Co(H2O)]2+ which is pink in colour.The net ionic reaction is-

CoCl42-(aq) + 6H2O(l) <--> Co(H2O)62+(pink) + 4Cl-

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