Qualitative Analysis of Carbohydrates

Question 1

most abundant organic compounds found in living organisms and are composed of carbon, hydrogen, and oxygen.

Answer 1

Carbohydrates

Question 2

act as the primary source to provide energy for functioning of living organisms

Answer 2

Carbohydrates

Question 3

considered as hydrates of carbon

Answer 3

carbohydrates

Question 4

general formula of Carbohydrates

Answer 4

Cx(H2O)y

Question 5

defined as polyhydroxy aldehydes or polyhydroxy ketones or the compounds which produces such products on hydrolysis

Answer 5

carbohydrates

Question 6

carbohydrates are defined as _________________________or the compounds which produces such products on hydrolysis

Answer 6

polyhydroxy aldehydes
polyhydroxy ketones

Question 7

Based on reactivity with Tollen’s, Benedict’s or Fehling’s reagent carbohydrates are classified as:

Answer 7

reducing sugars
non-reducing sugars

Question 8

carbohydrates that can reduce Tollen’s, Benedict’s or Fehling’s reagent are called _____________

Answer 8

reducing sugars

Question 9

sugar with free aldehyde or ketone group

Answer 9

reducing sugars

Question 10

true or false: all monosaccharides and most of the disaccharides are reducing sugars

Answer 10

true

Question 11

Carbohydrates that cannot reduce Tollen’s, Benedict’s or Fehling’s reagents are called

Answer 11

non-reducing sugars

Question 12

True or False: Maltose and Lactose are non-reducing sugars

Answer 12

False; reducing

Question 13

True or False: Sucrose is a reducing sugar

Answer 13

False; non-reducing

Question 14

What are the different tests for the detection of carbohydrates?

Answer 14

Molisch’s test
Fehling’s test
Benedict’s test
Tollen’s test
Iodine test

Question 15

10% alcoholic solution of α-naphthol

Answer 15

Molisch’s reagent

Question 16

What is used in Molisch’s test?

Answer 16

concentrated sulfuric acid

Question 17

carbohydrates undergo dehydration by sulfuring acid to form _______ that reacts with α-naphthol

Answer 17

furfural (furfuraldehyde)

Question 18

carbohydrates undergo dehydration by sulfuring acid to form furfural that reacts with α-naphthol to form a _______ colored product

Answer 18

violet

Question 19

carbohydrates undergo dehydration by sulfuring acid to form furfural that reacts with α-naphthol to form a violet colored product

Answer 19

molisch’s test

Question 20

Fehling’s A is a _____________ while Fehling’s B solution is potassium sodium tartrate

Answer 20

copper sulphate

Question 21

Fehling’s B solution is ___________ while Fehling’s A is copper sulphate

Answer 21

potassium sodium tartrate

Question 22

On heating, carbohydrate reduces deep blue solution of __________ to red precipitate of insoluble copper oxide

Answer 22

copper II ions

Question 23

On heating, carbohydrate reduces deep blue solution of copper II ions to red precipitate of insoluble ____________

Answer 23

copper oxide

Question 24

The copper ions present in Fehling’s solution in +3 state is reduced to _________________

Answer 24

+2 oxidation state

Question 25

In alkaline medium, copper ions present in Fehling's solution is precipitated as _____________

Answer 25

red cuprous oxide

Question 26

distinguishes reducing sugar from non-reducing sugar

Answer 26

Benedict's test

Question 27

Benedict's reagent contains

Answer 27

Blue copper (II) ions (Cu2 cupric ions)

Question 28

Benedict's reagent contains Blue copper (II) ions (Cu2 cupric ions) that are reduced to

Answer 28

copper (I) ions (Cu2+ cupric ions)

Question 29

In alkaline medium, __________ converts glucose to enediol which reduce cupric to cuprous forming cuprous hydroxide

Answer 29

sodium carbonate

Question 30

In alkaline medium, sodium carbonate converts __________ to enediol which reduce cupric to cuprous forming cuprous hydroxide

Answer 30

glucose

Question 31

In alkaline medium, sodium carbonate converts glucose to ________ which reduce cupric to cuprous forming cuprous hydroxide

Answer 31

enediol

Question 32

reduce cupric to cuprous forming cuprous hydroxide

Answer 32

enediol

Question 33

Where is the Benedict's solution kept?

Answer 33

sodium citrate

Question 34

upon boiling, Benedict's reagent forms

Answer 34

cuprous oxide

Question 35

ammoniacal silver nitrate solution

Answer 35

Tollen's reagent

Question 36

Carbohydrates reacts with Tollens reagent forms a ________ mirror on the inner walls of the test tibe

Answer 36

silver

Question 37

used to detect presence of starch

Answer 37

Iodine test

Question 38

True or False: Iodine is not much soluble in water

Answer 38

true

Question 39

Where is iodine solution prepared?

Answer 39

dissolving iodine in water in the presence of potassium iodide

Question 40

Iodine dissolved in an aqueous solution of potassium iodide reacts with starch to form a ____________ which gives characteristics blue black color

Answer 40

starch/iodine complex

Question 41

True or False: In iodine test, when heating the blue color disappears and on cooling the blue color reappears

Answer 41

True

Question 42

positive in molisch's test

Answer 42

maltose lactose sucrose

Question 43

negative on molisch's test

Answer 43

starch

Question 44

Fehling's test positive

Answer 44

maltose lactose sucrose

Question 45

Fehling's test negative

Answer 45

starch

Question 46

Benedict's test positive

Answer 46

maltose lactose sucrose

Question 47

Benedict's test negative

Answer 47

starch

Question 48

Tollen's test positive

Answer 48

maltose lactose

Question 49

Tollen's test negative

Answer 49

sucrose starch

Question 50

Iodine test positive

Answer 50

starch

Question 51

iodine test negative

Answer 51

maltose lactose sucrose