Question

identify the cation and avionics radical in given unknown salt performing dry and wet test for cationic redical and anionic redical

Answer 1

Dry Test :
Borax Bead Test:
This test is to be performed only for coloured salts.

Borax [Na2B407.10H20] on heating gets fused and loses water of crytsllisation.
After melting it forms colouless liquid which later forms a clear transparent bead consisting of boric anhydride and sodium metaborate.
Na2B407.10H2O -------> Na2B4O7 +10H2O

Na2B4O7----> B2O3 +2 Na BO2

Boric anhydride is non volatile.
When treated with coloured salt , a colour bead of metal carbonate is formed.

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*Metal Hot Cold
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copper Green Blue
Iron yellowish brown yellow
Chromium yellow green
Manganese Violet amethyst
Cobalt blue blue
Nickel Violet reddish brown
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Wet Test for Acid radicals :
salt is mixed with dil.H2SO4 and also with Conc.H2SO4
Based on the type of gas evolved . Inference is done .

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Observation Acid radical Confirmation Test
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1. evolution of CO₃²⁻ Gas turns lime water milky.colourless gas

2. Brown gas NO₂⁻ Add KI and starch solution. It turns blue colour

3. Smell of S₂⁻ Gas turns lead acetate paper blackrotten eggs

4.Pungent SO₃⁻ Turns acidiefed K2cR2O7 Sol green colourlessgas

5. Gives smell of CH3COO⁻ aq. +neutral FeCl2
vinegar gives blood red colour.

6.white/Yellow S₂O₃²⁻ aq.+AgNo3 white prpt ---> black.turbidity on warming

7. colourless Cl- add. MnO2 and heatpungent gas with white fumes pale green colour gas will be evolved

8. Reddish brown Br- add MnO2 and heatfumes brown gas is produed

9. Violet Pungentgas I- converts starch paper blue Layer test can be done
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Wet Test for Basic Radical :***************************************************************************************
Group Basic radicals Group Reagent Ppt as
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I Ag+, Hg2+, Pb2+ dil.HCl Chloride

II Cu2+,Cd2+,Pb2+,Hg2+ H2S gas +HCl Sulphides Bi3+,As3+, Sb3+ Sn2+

III Al3+,Cr3+Fe3+ NH4OH+NH4Cl Hydroxide

Iv Zn2+, Ni2+,Mn2+Co3+ H2S in Sulphides ammonical medium

V Ca2+,Ba2+ Sr2+ (NH4)2CO3 +NH4Cl Carbonates

VI Mg2+ ,Na+,K+ NH4OH , Na2HPO4 [for only Mg2+] white ppt

zero NH4+ ============ ***************************************************************************************