Page 78 - Chemistry - XI

VIVA VOCE

Q1. What is qualitative analysis?
Ans. The separation of materials into ingredients and to fi nd their kind is called qualitative analysis.

Q2. What is inorganic qualitative analysis?
Ans. The detection of cations (basic radicals) and anions (acid radicals) present in a salt or mixture of
inorganic compounds following a systematic scheme is called inorganic qualitative analysis.

Q3. What are odours of CO and SO ?
2 2
Ans. Co is odourless whereas SO has pungent smell or smell of burning sulphur.
2 2
Q4. Which ion gives violet colour with sodium nitroprusside?
Ans. Sulphide ion

Q5. Why is it necessary to confi rm the presence of phosphate in the fi ltrate of group II if As is
+3
present in your mixture?
3−
Ans. It is because both As and PO give yellow ppt. with ammonium molybdate.
+3
4
Q6. Why does organic layer get more dark coloured than the aqueous layer in the test of Br and
–
I ions?
–
Ans. It is because Br and I are more soluble in organic compound than water.
2
2
Q7. Why does KI and starch turns blue in test of NO ?
−
2
Ans. NO oxidises I ion to I which turns starch blue.
−
–
2 2
Q8. Which anion is indicated if there is evolution of brown fumes with dil H SO ?
2 4
Ans. NO (Nitrate ion)
−
2
Q9. Which gas turns lead acetate paper black and why?
Ans. H S, it is due to formation of PbS which is black ppt.
2
Q10. Which anion is indicated if there is evolution of brown fumes with conc. H SO ?
2 4
Ans. Br or NO −
−
3
Q11. Why is ZnS not precipitated in group II?
Ans. It is because K of ZnS is high, and in II group conc. of S is low in acidic medium due to common
2–
sp
ion eff ect.
Q12. How can we test the presence of NH ?
+
4
Ans. Heat salt with NaOH and if it gives white fume with glass rod dipped in conc. HCl, NH is present.
+
4
Q13. Why is it essential to boil off H S gas before the precipitation of group III radicals?
2
Ans. It is because if it is not removed, IV group radicals may get precipitated in III group.
Q14. Why should the solution be concentrated before it is proceeded to group V?
Ans. It is done to increase the conc. of cation so that ionic product exceeds K needed for precipitation.
sp
Q15.
Q15. Name the cation which is not obtained from a metal. Name the cation which is not obtained from a metal.
Ans. NH is the cation which is not obtained from metal. is the cation which is not obtained from metal.
Ans.
+ +
NH
4 4
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