Question

Identity two acidic and two basic radicals from organic mixture

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.

*************************************************************

*Metal Hot Cold

***************************************************************

copper Green Blue

Iron yellowish brown yellow

Chromium yellow green

Manganese Violet amethyst

Cobalt blue blue

Nickel Violet reddish brown

**********************************************************************

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 .

****************************************************************************************

Observation Acid radical Confirmation Test

****************************************************************************************

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

****************************************************************************************

Wet Test for Basic Radical :***************************************************************************************

Group Basic radicals Group Reagent Ppt as 

************************************************************************************* 

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+