Question

In early studies it was observed that when the complex [Co(NH3)4Br2]Br was placed in water, the electrical conductivity of a 0.05 M solution changed from an initial value of 191 ohm?1 to a final value of 374 ohm?1 over a period of an hour or so.

Suggest an explanation for the observed results.

Write a balanced chemical equation to describe the reaction.

A 500-mL solution is made up by dissolving 3.88g of the complex. As soon as the solution is formed, and before any change in conductivity has occurred, a 25.00?mL portion of the solution is titrated with 0.0100 M AgNO3 solution. What volume of AgNO3 solution do you expect to be required to precipitate the free Br?(aq)?

Based on the response you gave to part B, what volume of AgNO3 solution would be required to titrate a fresh 25.00?mL sample of [Co(NH3)4Br2]Br after all conductivity changes have occurred?

Answer 1

Conductivity (or specific conductance) of an electrolyte solution is a measure of its ability to conduct electricity. The SI unit of conductivity is siemens per meter (S/m).

Electrical conductivity is a measure of how well a material accommodates the movement of an electric charge. It is the ratio of the current density to the electric field strength.

Electrical conductance is an electrical phenomenon where a material contains movable particles with electric charge (such as electrons), which can carry electricity. When a difference of electrical potential is placed across a conductor, its movable charges flow, and an electric current appears. A Conductor such as a metal has high conductivity, and an insulator like glass or a vacuum has low conductivity.

So, for this solution which contains [Co(NH3)4Br2]Br , this compund is dissociated in its corresponding cation and anions  [Co(NH3)4Br2]+ and Br-. So, these ions help in increasing the electrical conductance of the system.