S1. Consider the following ions: Be2+; Cst; Ba2+; [Ba(crown ether)2+; Ga+; Re0A:

Question

S1. Consider the following ions: Be2+; Cst; Ba2+; [Ba(crown ether)2+; Ga+; Re0A: FeOs ; TeOs SiF (a) Assign each of the ions to one of the following six categories: nonacidic, feebly acidic, acidic, nonbasic, feebly basic, basic. (b) For each cation pick one of the following anions-ReOFeO42-·2-. TeO66-, siF62- that should give a water-insoluble salt with the cation; then write the formula of the resulting insoluble salt. (c) From the original list of anions and cations in this question, pick any combination that will produce a salt that is likely to be a good desicant. Write its formula. Why will this salt likely form a hydrate? S1C

Explanation / Answer

As the oxidation state on cation increases acidity also increases. That is as the size of cation decreases acidity increases. Therefore the decreasing order of acidity is

Re+7> Te+6> Si+4> Fe+3> Ga+3> Be+2> Ba+2> Ba(crown ether)+2> Cs+1> O2-

According to Lewis acid base concept all cations are acidic since they accept electrons. So in the above given ions cations with higher charge and smaller size have capacity to accept electrons easily. So the starting ions of the chronological order given are higly acidic followed by weakly acidic, acidic, non basic, weakly basic, basic.

Bases are those which give electrons easily hence anions are usually basic. Hence O2- although electronegative gives electrons to become oxides.

*Ba2+ with crown ether becomes less acidic than Ba2+ as crown ether is a big molecule and hinders Ba2+ from accepting electrons easily when compared to Free Ba2+ cation

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