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WAEC Chemistry 2019 Objective — Question 33

Question 33 of 50 from the West African Examinations Council (WAEC) Chemistry 2019 Objective paper, with the correct answer and a full explanation.

The oxidation number of chromium in Cr2O7²⁻ is

A. +4
B. +5
C. +6Correct
D. +7

Explanation

Let Cr = x: 2x + (7×–2) = –2 → 2x − 14 = –2 → 2x = 12 → x = +6.

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