Exp 5.5: Carbohydrates (Quanti Analysis)

Question 1

method used to measure amount of carbohydrates present in a given sample

Answer 1

Nelson’s method

Question 2

Nelson’s method basis

Answer 2

Based on capacity of the free reducing group of sugars to reduce Cu2+ in an alkaline solution

Question 3

Nelson’s method:
principle

Answer 3

● Sample = colorless
o Add reagents to oxidize the
reducing sugars into aldonic acids

Question 4

Nelson’s A reagents

Answer 4

Rochelle salt
● sodium potassium tartrate
● Na2CO3, NAHCO3, NA2SO4
● Will also keep Cu ions in solution

Question 5

Nelson’s B reagents

Answer 5

● CuSO4 x 5H2O
● H2SO4

Question 6

Nelson’s A and Nelson’s B principle:
oxidizing agent

Answer 6

CuSO4

Question 7

Nelson’s A and Nelson’s B principle:
makes sugars more reactive

Answer 7

Na2CO3 & NAHCO3

Question 8

Nelson’s A and Nelson’s B principle:
prevents precipitation of Cu(OH)2

Answer 8

NaKtartrate

Question 9

Nelson’s A and Nelson’s B principle:
why Nelson’s A and Nelson’s B are not mixed until before using

Answer 9

because NaKtartrate itself tend to reduce Cu2+ in time

Question 10

Ammonium Molybdate Regeant:
reagents

Answer 10

● (NH4)2MoO4
● H2SO4
● Na2HAsO4 x 7H2O

Question 11

Ammonium Molybdate Regeant principle:
Added to dissolve __________

Answer 11

Cu2O

Question 12

Ammonium Molybdate Regeant principle:
Converted into __________

Answer 12

molybdenum blue

Question 13

Ammonium Molybdate Regeant principle:
Intensity of blue coloration dependent on the?

Answer 13

amount of Cu2O formed