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Unformatted text preview: plain why the color changes during this process.
Question D: An excess of H2O2 has been used in this step since cobalt(II) is oxidized
in the presence of the decomposing hydrogen peroxide. In the reduction half reaction
of H2O2 in a basic solution hydroxide ions are formed, 2e- + H2O2(aq) 2OH-(aq).
Write a balanced ionic equation for the redox reaction occurring in step 4.
As a side note: The decomposition of hydrogen peroxide takes place as self-reaction
involving both oxidation and reduction processes. Therefore, a by-product reaction
occurring here is 2 H2O2(aq) 2 H2O(l) + 2O2(g). This reaction is catalyzed by
the presence of transition metal ions.
5. Place the small casserole over the 250 mL beaker that is partially filled with the
boiling water (use a hot plate to boil water). Be careful to avoid breathing the vapors
that may rise out of the casserole. Next, quickly but carefully, add 12 mL of
concentrated HCl and note any color changes. Continue heating the casserole on top
of the beaker for about 50 minutes. During the 50 m...
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- Spring '07