Page 79 - Chemistry - XI

Q16. What is the composition of dark brown ring which is formed at the function of low layers in
ring test for NO ?
−
3

Ans. Fe HO NO SO 4

2
5
Q17. Why do bromide and iodides do not give test similar to chromyl chloride test?
Ans. It is because HBr and HI get oxidised by conc. H SO and K Cr O .
2
4
2
7
2
Q18. How will you test the presence of S ?
2–
Ans. Add dil. H SO to solid salt and bring a paper applied in lead acetate solution, if it turns black, S 2−
2
4
is indicated.
Q19. What is Nessler's reagent?
Ans. It is a solution prepared by combining sodium hydroxide, potassium iodide, and mercuric chloride.
Its chemical formula is K HgI .
4
2
Q20. How can one prevent the precipitation of Group IV radicals with second group radicals?
Ans. It is done by passing H S gas in acidic medium, i.e. in presence of dil. HCl, S decreases due to
2–
2
common ion eff ect insuffi cient to precipitate III group radical, but can easily precipitate group II
radicals.
Q21. Name the anions detected by conc. H SO .
4
2
−
−
−
Ans. NO , Cl , Br , I −
3
Q22. How is soda extract prepared?
Ans. Salt is mixed with equal amount of Na CO . Heated, cooled, and fi ltered to get soda extract.
2
3
Q23. Why is AgNO stored in dark coloured bottle?
3
Ans. It is because it may get decomposed in the presence of sunlight.
Q24. Can we use glass rod instead of platinum wire while performing fl ame test? Give reason.
Ans. No, because glass rod itself may impart yellow colour due to presence of sodium.

Q25. CO and SO gas both turn lime water milky. How would you distinguish between the two?
2
2
Ans. CO is odourless where SO has pungent smell or burning sulphur which causes coughing.
2 2
Q26. What is the diff erence between a qualitative and quantitative analysis?
Ans. Qualitative analysis involves the names of constituents present in a mixture where as quantitative
analysis determines the amount of constituent in a compound or in a mixture.

Q27. Why is sometimes a precipitate obtained in VI group even if Mg ion is not present?
2+
Ans. The radicals of group V and lower groups if not precipitated, get precipitated in group VI.

Q28. Can NaCl and NaOH show common ion eff ect? Why?
Ans. No, they do not show common ion eff ect because both of them are strong electrolytes.

Q29. Can we add NH OH before adding NH Cl in group III ?
4
4
Ans. No, when NH OH is added fi rst, common ion eff ect of NH Cl is absent, therefore, cations of other
4
4
group will also precipitate.

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