Pract. Chem

Question 1

Organic compounds generally consist of

Answer 1

Carbon & hydrogen

Question 2

Other elements which may be present in organic compounds are

Answer 2

Oxygen, nitrogen, halogen & sulphur

Question 3

Lassaigne’s test is preferred to confirm the presence of

Answer 3

Nitrogen, chlorine, bromine, iodine, sulphur

Question 4

Lassaigne’s extract is

Answer 4

Salt fused with sodium metal to prepare water soluble salt, also called sodium fusion extract

Question 5

Sodium thiocyanate is formed when

Answer 5

Possible only when sodium metal is in little amount (nitrogen & sulphur, both are present)

Question 7

Prussian blue precipitate indicates presence of

Answer 7

Nitrogen

Question 8

Sodium extract formula

Answer 8

NaCN (sodium cyanide)

Question 9

Oxidation state of iron in sodium hexacyanoferrate / sodium ferrocyanide

Answer 9

+2 {Na4[Fe(CN)6]}

Question 10

Oxidation state of iron in Prussian blue

Answer 10

Ferric ferrocyanide [iron hexacyanoferrate]
Fe4[Fe(CN)6]3 => +3 & +2

Question 12

Violet colour confirms the presence of

Answer 12

Sulphur

Question 13

Sodium nitroprusside

Answer 13

Na4[Fe(CN)5NOS] - presence of sulphur

Question 14

Black ppt of lead sulphide (Pbs) confirms the presence of

Answer 14

Sulphur

Question 15

Formation of blood red colour confirms the presence of

Answer 15

Both nitrogen and sulphur

Question 16

Appearance of blood red colour

Answer 16

Ferric sulphocyanide
Fe(SCN)3

Question 17

White ppt which is soluble in ammonium hydroxide (insoluble in HNO3) confirms the presence of

Answer 17

Chlorine

Question 18

Yellow ppt - partially soluble in ammonium hydroxide confirms the presence of

Answer 18

Bromine

Question 19

Dark yellow ppt - insoluble in ammonium solution indicates the presence of

Answer 19

Iodine

Question 20

In layer test (sodium fusion extract + ccl4+ Cl water)

Answer 20

Orange layer - presence of Br
Violet layer - presence of I

Question 21

Ceric ammonium nitrate test confirms

Answer 21

(Red coloration) - alcoholic group

Question 22

Lucas reagent (ZnCl2 + conc.HCl)

Answer 22

1° alcohol = no reaction
2° alcohol = turbidity within minutes
3° alcohol = immediate turbidity

Question 23

Iodoform test - given by

Answer 23

Compounds having α- methyl group

Question 24

Confirmation iodoform test

Answer 24

Yellow ppt of iodoform

Question 25

Phenols form which coloured complex with freshly prepared FeCl3 solution

Answer 25

Violet

Question 26

Violet/ blue coloration, given by

Answer 26

Resorcinol, o-, m-, p- cresol

Question 27

Catechol gives which colour

Answer 27

Green (rapidly darkness)

Question 28

1 and 2- naphthol - which colour

Answer 28

Do not show characteristic colour

Question 29

Phenol condenses with phthalic anhydride in the presence of conc. H2SO4 to give

Answer 29

Phenolphthalein (gives dark pink colour with NaOH soln) --- called phthalein dye test

Question 30

2,4-DNP test

Answer 30

Yellow - aldehyde Red - ketone

Question 31

2, 4-DNP reacts with aldehyde and ketones to give

Answer 31

DNP( Hydrazone)

Question 32

Schiffs test, felhings test, tollens test are given by

Answer 32

Aldehydes only

Question 33

Felhings A

Answer 33

Aq. Cuso4

Question 34

Felhings b

Answer 34

Alk. Sodium potassium tartarate (Rochelle's salt)

Question 35

Cupric ions of copper tartarate oxidises aldehydes to

Answer 35

Carboxylic acid (orange red ppt of Cu2O) Ketone- unaffected

Question 36

Aromatic aldehydes with felhings

Answer 36

Don't give positive fehlings test

Question 37

Benedict solution

Answer 37

Alk. (Copper sulphate+ sodium citrate) More stable than fehlings solution & can be stored for longer duration

Question 38

Schiffs test prepared by

Answer 38

Decolourising aq. Soln of p- rosaniline hydrochloride dye (adding sodium sulphite or passing SO2 gas in it)

Question 39

Pink colour of schiffs indicate

Answer 39

Presence of aldehyde group