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WAEC Chemistry 2015 Theory — Question 15

Question 15 of 49 from the West African Examinations Council (WAEC) Chemistry 2015 Theory paper, with the correct answer and a full explanation.

2(a)(iv). Write the formula of the compound formed when R combines with X.

Model answer

Using the group/valency of R and X (as deduced from their electronic configurations in the table), the formula of the compound formed is derived by cross-balancing their combining powers/valencies, e.g. X₂R or XR depending on their respective valencies.

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