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Calculate the oxidation number of the underlined atom. Cr2O72−

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Question

Calculate the oxidation number of the underlined atom.

Cr2O72−

Numerical
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Solution

Cr2O72−

Oxidation of O = –2

\[\ce{Cr2O^2-_7}\] is an ionic species.

∴ Sum of the oxidation numbers of all atoms = – 2

∴ 2 × (Oxidation number of Cr) + 7 × (Oxidation number of O) = – 2

∴ 2 × (Oxidation number of Cr) + 7 × (–2) = – 2

∴ 2 × (Oxidation number of Cr) – 14 = – 2

∴ 2 × (Oxidation number of Cr) = – 2 + 14

∴ Oxidation number of Cr = `+12/2`

∴ Oxidation number of Cr in \[\ce{Cr2O^2-_7}\] = +6

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Chapter 6: Redox Reactions - Exercises [Page 92]

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Balbharati Chemistry [English] Standard 11 Maharashtra State Board
Chapter 6 Redox Reactions
Exercises | Q 3. (C)(f) | Page 92

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