## General Chemistry (4th Edition)

Published by University Science Books

# Chapter 26 The Chemistry of the Transition Metals - Problems - Page 1017: 6

#### Answer

First, Chromium(II) rapidly reduces O2(g) to water and forms chromium(III): $2 Cr^{3+}(aq) + Zn(s) → 2 Cr^{2+}(aq) + Zn^{2+}(aq)$ Then, chromium(III) is reduced back to chromium(II) by the zinc: $4 Cr^{2+}(aq) + 4 H^{+}(aq) + O_{2}(g) → 4 Cr_{3}+(aq) + 2 H_{2}O(l)$

#### Work Step by Step

First, Chromium(II) rapidly reduces O2(g) to water and forms chromium(III): $2 Cr^{3+}(aq) + Zn(s) → 2 Cr^{2+}(aq) + Zn^{2+}(aq)$ Then, chromium(III) is reduced back to chromium(II) by the zinc: $4 Cr^{2+}(aq) + 4 H^{+}(aq) + O_{2}(g) → 4 Cr_{3}+(aq) + 2 H_{2}O(l)$

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