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The oxidation number of Chromium in Na\(_2\)Cr\(_2\)O\(_7\) is 

Chemistry
WAEC 2024

The oxidation number of Chromium in Na\(_2\)Cr\(_2\)O\(_7\) is 

  • A. +2
  • B. +6
  • C. +7
  • D. +12
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Correct Answer: Option B
Explanation

Oxidation number of Cr in Na\(_2\)Cr\(_2\)O\(_7\) = 0

                                          2(Na) + 2Cr + 7(O) = 0

Oxidation state of Na = +1, O = - 2

So,   2(+1) + 2Cr +  7(-2) = 0

         +2 + 2Cr - 14 = 0

          +2 - 14 + 2Cr = 0

           - 12 + 2Cr = 0

               2Cr = 12

                Cr = \(\frac{12}{2}\)

                 Cr = + 6


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