From the following salts, list those which, considered individually, would behav

Question

From the following salts, list those which, considered individually, would behave in the manner indicated for each case below: CaCO_3, (NH_4)_ CO_3, Zn_3(PO_4)_, Ag_2 CO_3, Ca(OH)_3, Hg_ Cl_2, FeCl_2, AgCl, AlCl_2, BaSO_4, Ba(NO_ ) Pb(NO__3)_ (a) Dissolves readily in water alone _____ (b) Dissolves readily in water, but forms a precipitate with excess NH_3 _____ (c) Is insoluble in water, but dissolves when excess HNO_3 is added _____ (d) Is insoluble in water, but dissolves when excess NH_3 is added _____ (e) Will not dissolve in water, or when either HNO_3 or NH_2 is added _____ An unknown solution is to be tested for the ions, or their derivatives, listed at the right. On the basis of the following tests, performed on separate portions of the unknown and considered as a whole, mark in column I a plus sign (+) if the ion is definitely present, a minus sign if the ion is definitely absent, or a question mark (?) if there is no evidence to prove the ion present or absent. (a) Phenolphthalein gives a red color. (b) When a test portion is warmed, red litmus held at the mouth of the test tube turns blue. (c) Acidifying a test portion with HNO_3 causes vigorous effervescence and the formation of a white precipitate, which dissolves when excess NH_3 is added to the mixture. (d) Addition of Na_2SO_4(aq) causes no visible effect. A second unknown solution is to be tested for the same list of ions at the right. On the basis of the following tests, considered as a whole, mark in column II, a plus sign, a minus sign, or a question mark, for each ion in the list, as in Problem 2. (a) Methyl orange gives a red color. (b) Addition excess Cl^- to one sample, and or SO_4^ to another sample, gives a white precipitate in each sample. (c) The Cl^- precipitate from (b), treated with NH_3(aq). turns black. (d) A sample is treated with excess Cl^- and filtered, and the filtrate is made basic with NH_3(aq), giving an orange-red precipitate.

Explanation / Answer

1)a) Dissolves readily in water- alone------>AlCl3,Ba(NO3)2,Pb(NO3)2

b)Dissolves readily in water,but forms precipitate with excess NH3---->(NH4)3CO3

c)Is insoluble in water ,but dissolves when excess HNO3 is added--->CaCO3,Zn3(PO4)2,Ag2CO3,Ca(OH)2,

d)Is insoluble in water ,but dissolves when excess NH3 is added---->Zn3(PO4)2,Hg2Cl2,FeCl3,AgCl

e)will not dissolve in water or when excess NH3 or HNO3 is added--->BaSO4

Solubility of salts in water depends on their ionic character,higher ionic character more soluble it is =mostly Chlorides,nitrates are soluble ,while Carbonates are sparingly soluble ,and sulfates are insoluble

Solubility of salts in HNO3 (strong acid) depends on their basic nature. If they are salts of strong base and weak acid then they hydrolyse in solution to give a basic solution.Alternatively, reaction may also occur between the cation and HNO3 ,hence they dissolve.

Solubility of salts in NH3 (weak base) depends on the acidity of the salts.If they are salts of strong acid and weakbase ,then they form acidic solution ,hence dissolves.A reaction may also occur between the NH3 and the anion,hence they dissolve.

CaCO3=slightly soluble in water,salt of slightly weak base Ca(OH)2 and weak acid H2CO3-forms basic solution so dissolves in acidic solutions

feCl3-lewis acid ,dissolves in basic NH3

AlCl3 - soluble in water,ionic in nature,but neutral salt of equally strong acid HCl and base Al(OH)3

nitrates dissolve in water, but in nitric acid they do not dissolve due to commn ion effect.

Hg2Cl2 ---> acidic salt of HCl and Hg2(OH)2 so dissolves in basic NH3

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