Question

Dry and wet test of cation of caco3

Answer 1

Identify Any one cation and anion from the following given salt.(a)CaCO3 (b)BaCl2 (c)ZnS (d)Pb(NO3)2 (e)FeCl3 1.physical characteristic,2.dry and wet test for cation ,3.dry and wet test for anion ,4.confirmatory test for cation and anion



Here we take calcium carbonate to identify of cation and anion. You can use other ones .

(a) Identification of cation in CaCO3 : here Calcium is cation and carbonate is anion. calcium present in fifth group.Solution of the fifth group precipitate in acetic acid gives a white precipitate with ammonium oxalate solution.
CaCO3 + 2CH3COOH ---> (CH3COO)2 Ca + H2O + CO2
(CH3COO)2Ca + (NH4)2C2O4 ----> (COO)2Ca + 2CH3COONH4
Here, (NH4)2C2O4 is ammonium oxalate and (COO)2Ca is white precipitation of calcium oxalate.
flame test : Calcium imparts
brick red colour to the flame which looks greenish-yellow through blue glass.

Identification of anion in CaCO3 : CO3²-, (carbonate ) is anion in the presence of calcium carbonate. If there is effervescence with the evolution of a colourless and odourless gas on
adding dil. H2SO4 to the solid salt, this indicates the presence of carbonate ion.
The gas turns lime water milky due to the formation of CaCO3.
Na2CO3 + H2SO4 ---> Na2SO4 + H2O +CO2
Ca(OH)2 + CO2 ----> CaCO3 + H2O

If CO2 gas is passed in excess through lime water, the milkiness produced
disappears due to the formation of calcium hydrogen carbonate which is soluble
in water.
CaCO3 + CO2 + H2O-----> Ca(HCO3)2.

Answer 2

When calcium and carbon are to be tested there is a dry and wet test using the litmus paper.

Dry test

Calcium turns blue litmus paper red

The carbon turns blue litmus paper blue

Wet test

Wet blue litmus paper changes to red while red litmus paper remains red

In carbon, wet litmus papers maintains there colours