Lab - Determination of Nitrogen/Crude Protein Flashcards Preview

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Flashcards in Lab - Determination of Nitrogen/Crude Protein Deck (14)
1

What method was used in the experiment?

Kjeldahl technique

2

To be more specific, the ____ modification of the Kjeldahl technique was used

Winkler

3

three phases of the Winkler modification of the Kjeldahl technique

digestion with acid
distillation to release the ammonia
titration with standard sulfuric acid

4

digestion phase involves decomposition of organic nitrogen compounds c/o of which acid?
A. hydrochloric
B. boric
C. sulfuric
D. muriatic

C

5

in acid digestion phase, organic C and H become

CO2 and H2O

6

in acid digestion phase, H2SO4 reduced into SO2. SO2 reduces nitrogenous material into __

ammonia

7

in acid digestion, reduction in time is done y adding K2SO4 or Na2SO4. Why?

they may raise the boiling point of the mixture

8

in the distillation stage to release ammonia, what acid is used?
A. hydrochloric
B. boric
C. sulfuric
D. muriatic

B

9

protein is assumed to have __% of Nitrogen

16

10

What indicator was used in the experiment?
A. phenolphthalein
B. methylene red
C. bromcresol-green

C

11

What distillation apparatus was used?

Markham distillation apparatus

12

Methods for determining nitrogen & crude protein are directly based on
A. Speed of result delivery
B. Presence of Functional groups in the molecule
C. Both A & B

B

13

The ultimate reference method for determining the concentration of protein is the ___

Analysis of Nitrogen content

14

In titration stage of Winkler modif of Kjeldahl technique, why is boric acid added?

To trap ammonia; it is too weak to affect H+ concentration