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Water and Phenolphthalein HIn <------> In^- + H^+ Reaction: Clear Pink 1. After

ID: 487346 • Letter: W

Question

Water and Phenolphthalein HIn <------> In^- + H^+ Reaction: Clear Pink 1. After the addition of 6 M HCl to the test tube, what is the color of the solution? How does the addition of HCl affect the equilibrium of the reaction above? How does this relate to the change, if any, in the color of the solution? Include equations for reactions in your explanation. 2.After the addition of 6 M NaOH to the test tube, what is the color of the solution? How does the addition of NaOH affect the equilibrium of the reaction? How does this relate to the change, if any, in the color of the solution? Include equations for reactions in your explanation.

Explanation / Answer

HIn <---> In^- +   H^+

When HCl is added, color of the solution will become clear. Adding HCl means adding H+. As a result, the equilibrium is shifted towards left hand side and less and less amount of In^- is present. Indicator shows color in its charged form. In its uncharged form it is colorless. So, when the equilibrium is shifted to left, color changes

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When NaOH is added, OH- reaction with H+ to form H2O .As a result the above equilibrium is shifted towards the right hand side. More and more In^- is formed. The solution turns pink.