Practical Organic Chemistry — Page 7 | JEE Chemistry

Q61

Which of the following compound is added to the sodium extract before addition of silver nitrate for testing of halogens?

A Nitric acid

B Sodium hydroxide

C Ammonia

D Hydrochloric acid

Correct Answer

Option A

Solution

NaCN + HNO3 $\to$ NaNO3 + HCN $\uparrow$ Na2S + HNO3 $\to$ NaNO3 + H2S $\uparrow$ Nilnic acid decomposed NaCN & Na2S, else they precipitate in test & misquite the resolve For testing of halogens, Nitric acid is added to the sodium extract because if CN– or S2– are present then they will be oxidised and removed before the test of halides.

Q62

Which of the following is 'a' FALSE statement ?

A Carius method is used for the estimation of nitrogen in an organic compound.

B Kjeldahl's method is used for the estimation of nitrogen in an organic compound.

C Carius tube is used in the estimation of sulphur in an organic compound.

D Phosphoric acid produced on oxidation of phosphorus present in an organic compound is precipitated as Mg2P2O7 by adding magnesia mixture.

Correct Answer

Option A

Solution

Carius method is used in the estimation of halogen and sulphur in organic compounds.

Q63

Match with : Test/Reagents/Observation(s) Species detected

List - I		List - II
(a)	Lassaigne's Test	(i)	Carbon
(b)	Cu	(II)	oxide
(c)	Silver nitrate	(ii)	Sulphur
(d)	The sodium fusion extract gives black precipitate with acetic acid and lead acetate	(iii)	N, S, P, and halogen
()		(iv)	Halogen Specifically The correct match is :

A (a)-(iii), (b)-(i), (c)-(ii), (d)-(iv)

B (a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)

C (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)

D (a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)

Correct Answer

Option C

Solution

(i) Lassaigne test is used to detect N, S, P, X element (ii) Carbon and hydrogen are detected by heating the compound with copper (ii) oxide. (iii) Halides are detected by silver nitrate (iv) Sodium fusion extract gives black ppt. with acetic acid and lead acetate to confirm the presence of sulphur.

Q64

Reagent, 1-napthylamine and sulphanilic acid in acetic acid is used for the detection of

A N2O

B NO

_3^ -

C NO

D NO

_2^ -

Correct Answer

Option D

Solution

1-naphthyl amine and sulphanilic acid in acetic acid is used for the detection of

NO_2^ -

.

Q65

An inorganic Compound 'X' on treatment with concentrated H2SO4 produces brown fumes and gives dark brown ring with FeSO4 in presence of concentrated H2SO4. Also Compound 'X' gives precipitate 'Y', when its solution in dilute HCl is treated with H2S gas. The precipitate 'Y' on treatment with concentrated HNO3 followed by excess of NH4OH further gives deep blue coloured solution, Compound 'X' is :

A Co(NO3)2

B Pb(NO2)2

C Cu(NO3)2

D Pb(NO3)2

Correct Answer

Option C

Solution

Compound ‘X’ is copper nitrate, i.e.

Cu(NO3)2 is an inorganic compound.

On treatment with concentrated H2SO4 produces brown fumes and gives dark brown ring with FeSO4 in presence of concentrated H2SO4.

Chemical reaction is as follows Cu2+ is a group II cation with group II reagents (HCl/H2S) , it gives black coloured precipitates.

These precipitates gives blue colour solution on treatment with HNO3 followed by excess of NH4OH.

Q66

In Carius method, halogen containing organic compound is heated with fuming nitric acid in the presence of :

A HNO3

B AgNO3

C CuSO4

D BaSO4

Correct Answer

Option B

Solution

Organic compound is heated with fuming nitric acid in the presence of silver nitrate in carius method.

Lunar caustic (AgNO3) is used as reagent hare to distinguish Cl $-$ , Br- and I $-$ respectively as follows.

C{l^ - }(aq)\overset{{AgN{O_3}}}\longrightarrow AgCl{ \downarrow _{ppt}}

white

B{r^ - }(aq)\overset{{AgN{O_3}}}\longrightarrow AgBr{ \downarrow _{ppt}}

pale yellow

{I^ - }(aq)\overset{{AgN{O_3}}}\longrightarrow AgI{ \downarrow _{ppt}}

Dark yellow

Q67

Which one of the following complexes is violet in colour?

A [Fe(CN)6]4

-

B [Fe(SCN)6]4

-

C Fe4[Fe(CN6)]3 . H2O

D [Fe(CN)5NOS]4

-

Correct Answer

Option D

Solution

(a) [Fe(CN)6]4 $-$ $\to$ Pale yellow solution (b) [Fe(SCN)6]4 $-$ $\to$ Blood red colour (c) Fe4[Fe(CN6)]3 .

H2O $\to$ Prussian blue (d) [Fe(CN)5NOS]4 $-$ $\to$ Violet colour

Q68

Which one of the following tests used for the identification of functional groups in organic compounds does not use copper reagent?

A Barfoed's test

B Seliwanoff's test

C Benedict's test

D Biuret test for peptide bond

Correct Answer

Option B

Solution

In Seliwanoff's reagent, Cu is not present. In Barfoed, Biuret and in Benediet reagent Cu is present.

Q69

The formula of the purple colour formed in Laissaigne's test for sulphur using sodium nitroprusside is :

A NaFe[Fe(CN)6]

B Na[Cr(NH3)2(NCS)4]

C Na2[Fe(CN)5(NO)]

D Na4[Fe(CN)5(NOS)]

Correct Answer

Option D

Solution

$\left.\mathrm{S}^{2-}+\left[\mathrm{Fe}(\mathrm{CN})_{5} \mathrm{NO}\right)\right]^{2-} \rightarrow\left[\mathrm{Fe}(\mathrm{CN})_{5}(\mathrm{NOS})\right]^{4-}$

Q70

Given below are two statements : Statement I : In 'Lassaigne's Test', when both nitrogen and sulphur are present in an organic compound, sodium thiocyanate is formed. Statement II : If both nitrogen and sulphur are present in an organic compound, then the excess of sodium used in sodium fusion will decompose the sodium thiocyanate formed to give NaCN and Na2S. In the light of the above statements, choose the most appropriate answer from the options given below :

A Both Statement I and Statement II are correct.

B Both Statement I and Statement II are incorrect.

C Statement I is correct but Statement II is incorrect.

D Statement I is incorrect but Statement II is correct.

Correct Answer

Option A

Solution

Both statement I & statement II are correct $\mathrm{NaSCN}+2 \mathrm{Na} \rightarrow \mathrm{NaCN}+\mathrm{Na}_{2} \mathrm{~S}$