Question

the following equilibrium is established when copper ions and bromide ions are placed in solution. heat cu(h2o)6 2 4 br- 6 h2o cubr4-2 the tube on the left contains only copper sulfate dissolved in solution. the tube on the right is the result of adding some potassium bromide solution. given that the cu(h2o)6 2 ion is blue and that the cubr4-2 ion is green, answer the questions below. a. what happened to the concentration of each of the ions when the kbr was added? b. explain why the solution changed color.

Answer 1

Adding KBr to a copper sulfate solution causes a shift in equilibrium due to the common ion effect, increasing the concentration of CuBr4 2- and decreasing the [Cu(H2O)6]2+, thereby changing the solution color from blue to green.

Step-by-step explanation:

When Potassium Bromide (KBr) was added to the copper sulfate solution, there was a shift in equilibrium due to the common ion effect. The common ion effect, which is a consequence of Le Chatelier's principle, predicts that the solubility of a compound will decrease in the presence of a common ion. Since bromide ions are common to both KBr and CuBr, the addition of KBr will cause the concentration of copper(II) bromide complex ions (CuBr42-) to increase, while the concentration of hydrated copper(II) ions ([Cu(H2O)6]2+) decreases. This change in concentration leads to the observed color change from blue to green; the blue color is characteristic of the hydrated copper(II) ions, while the green color is characteristic of the copper(II) bromide complex ions.