I. 1. What can you conclude about the reaction 2CrO42-(aq) à Cr2O72-(aq) and its dependence on H+(aq)? Balance this equation by adding the proper number of H+ ions and H2O molecules.
2. What can you conclude about the reaction Cr2O72-(aq) à 2CrO42-(aq) and its dependence on OH-(aq)? Balance this equation by adding the proper number of OH- ions and H2O molecules.
II. 1. What can you conclude about the relative equilibrium concentrations of CrO42-(aq) in each of the solutions of 0.1 M K2CrO4 and 0.1 M K2CrO7?
2. Use the equations you balanced in questions 1 and 2 of part I to explain the results you’ve obtained in steps d and e of part II.
3. Summarize in 1 to 2 sentences your result with chromate-dichromate equilibrium and its application of Le Chatelier’s principle.
III. 1. (a) Which substances in solution caused the color to change from that of the Cr2O72-(aq) ion to that of CrO42-(aq) ion? (b) Which substances in solution cause the reverse color change?
2. What ionic species do the solutions you listed in question 1a have in common? In question 1b?
3. Give an explanation of the results you noted when (a) ethyl alcohol was added, (b) the solution of NH3(aq) was added.
4. On the basis of your conclusion made in question 2, predict some additional substances which solution might have the same effect on the 2CrO42-(aq) ↔ Cr2O72-(aq) equilibrium as those you categorize in questions 1a and 1b.
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