WAEC Chemistry 2010 Theory — Question 4
Question 4 of 46 from the West African Examinations Council (WAEC) Chemistry 2010 Theory paper, with the correct answer and a full explanation.
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1(b) The electron configuration of an element X is 1s²2s²2p⁶3s²3p⁵. (i) Deduce the atomic number of X. (ii) To what group does X belong? (iii) Give two properties of the element which X belongs to. (iv) Identify element X by name. (v) Write a balanced equation to represent the reaction between the element X and hot concentrated NaOH.
Model answer
(i) The atomic number of X is 17. (ii) Group (VII). (iii) Properties: they form monovalent negative ions; they are highly electronegative; they are very good oxidizing agents. (iv) X is chlorine. (v) 3Cl2(g)+6NaOH(aq)→5NaCl(aq)+NaClO3(aq)+3H2O(l).
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