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WAEC Chemistry 2024 Paper

Question : 5

Total: 50

_{2}

_{2}

_{7}

Solution:

Concept:

The sum of oxidation numbers of all atoms in a neutral compound is zero.

Explanation:

Let the oxidation number of chromium be

x

The oxidation number of sodium is

+1

The oxidation number of oxygen is

-2

For

\mathrm{Na}_2\mathrm{Cr}_2\mathrm{O}_7

, the equation is:

2(+1) + 2x + 7(-2) = 0

This simplifies to:

2 + 2x - 14 = 0

2x - 12 = 0

2x = 12

x = +6

Answer:

The oxidation number of Chromium in

\mathrm{Na}_2\mathrm{Cr}_2\mathrm{O}_7

+6

Correct option: B.

+6

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