Page 87 - Chemistry - XI

3NaSCN + FeCl 3 Fe(SCN) + 3NaCl
3
Ferric thiocyanate
(Blood red colour)
NaCN + HNO 3 NaNO + HCN
3
Na S + 2HNO 3 2NaNO + H S
3
2
2
Ag + Cl – AgCl
+
(White ppt.)
AgCl + 2NH 3 [Ag(NH ) ]Cl
3 2
(NH OH) (Soluble)
4
Ag + Br – AgBr
+
(Yellow ppt.)
Ag + I – AgI
+
(Dark yellow ppt.)
Precautions
1. Sodium metal is highly reactive, so it should be handled with care. It should not be touched with
moist fi ngers.

2. Before using sodium metal, it should be soaked within the folds of the fi lter papers.
3. During the fusion, the ignition tube should be dry because sodium metal can react with water vigorously.
4. Cover the china dish with a wire gauze while putting hot ignition tube into water.

VIVA VOCE

Q1. What happens when sodium fuses with the organic compound?
Ans. It changes to ionic compound.
Q2. Is sodium extract acidic or alkaline in nature?
Ans. It is alkaline in nature.

Q3. Why is it necessary to acidify the sodium extract before performing AgNO test?
3
Ans. It is done so as to decompose Na S to H S and NaCN to HCN.
2
2
Q4. Why is freshly prepared solution of ferrous sulphate used in testing of nitrogen?
Ans. It is used because ferrous sulphate solution gets oxidised to ferric sulphate if it is kept in presence
of air.
Q5. Why only freshly cut sodium is used in the fusion mixture?
Ans. Sodium piece, if kept, it will get oxidised to Na O which reacts with CO to form Na CO .
2 2 2 3
Q6. If we get blood red colour in the test for nitrogen, what does it show?
Ans. Both ‘N’ and ‘S’ are present.

Q7. Why is H SO (dil) added in the detection of nitrogen?
2
4
Ans. It is added so as to dissolve green ppt. of Fe(OH) and to oxidise Fe to Fe .
3+
2+
2
Q8. What will be the colour of the CCl if chlorine is present in the organic compound in chlorine if chlorine is present in the organic compound in chlorine
4
water test?
Ans. It will remain colourless because no reaction will take place.
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