(time=2 +5+4+1+3 = 15 minutes] Suppose a solution of chromium in 1 Macid is knocked over and its contents are spilt. Us...
(time=2 +5+4+1+3 = 15 minutes] Suppose a solution of chromium in 1 Macid is knocked over and its contents are spilt. Use the Question 6 Pourbaix diagram below to answer the following questions Cr O, Cro 10 0.5 Cr 00 Cr(OH) 05 -10 Cr -1.5 2 10 12 14 pH What is the predominant form of chromium in 1 M acid in contact with the air? (a) (b) Write a balanced redox equation between the two highest oxidation states of chromium shown in the Pourbaix diagram in I M acid and identify the pH dependence of the redox couple over the pH range 0 to 3.9. (c) Why does the pH dependence of the redox couple linking the two highest oxidation states of chromium shown in the Pourbaix diagram change when the pH increases above 3.9? What is the pH dependence of the couple in the pH region 3.9 to 7.5? (d) Does chromium in its highest oxidation state become a stronger or weaker oxidising agent at higher pH conditions? (e) Chromium(VI) is a known carcinogen whereas chromium(II) is benign in biological environments. What are the conditions (if any) when chromium(VI) is likely to be stable in the environment (fresh and sea water)? If so what are the predominant chromium(VI) species under these conditions?
(time=2 +5+4+1+3 = 15 minutes] Suppose a solution of chromium in 1 Macid is knocked over and its contents are spilt. Use the Question 6 Pourbaix diagram below to answer the following questions Cr O, Cro 10 0.5 Cr 00 Cr(OH) 05 -10 Cr -1.5 2 10 12 14 pH What is the predominant form of chromium in 1 M acid in contact with the air? (a) (b) Write a balanced redox equation between the two highest oxidation states of chromium shown in the Pourbaix diagram in I M acid and identify the pH dependence of the redox couple over the pH range 0 to 3.9. (c) Why does the pH dependence of the redox couple linking the two highest oxidation states of chromium shown in the Pourbaix diagram change when the pH increases above 3.9? What is the pH dependence of the couple in the pH region 3.9 to 7.5? (d) Does chromium in its highest oxidation state become a stronger or weaker oxidising agent at higher pH conditions? (e) Chromium(VI) is a known carcinogen whereas chromium(II) is benign in biological environments. What are the conditions (if any) when chromium(VI) is likely to be stable in the environment (fresh and sea water)? If so what are the predominant chromium(VI) species under these conditions?