Sunday, April 21, 2013

CBSE Class 9: Science Experiment (SA1) - Test the presence of adulterant metanil yellow in dal (MCQs)

Test the presence of adulterant metanil yellow in dal 

CBSE Class 9: Science Experiment - Test the presence of adulterant metanil yellow in dal (MCQs)
Metanil yellow is a synthetic dye which is not permitted to use as food colour. However it is used extensively in India to give yellow colour to Dal (pulses) and turmeric. Metanil yellow is toxic by nature and it has adverse effects on liver, intestine and brain.

To test the presence of metanil yellow in dal, take the following steps:
  1. Take approximately 5 gms of dal in a test tube and add 5 ml of water. 
  2. Shake the test tube well. 
  3. Add few drops of concentrated hydrochloric acid to the test tube. (This activity should be done in the presence of your school teacher).
  4. The appearance of a pink colour in the solution confirms the presence of metanil yellow in dal


(MCQs asked in CBSE examination)

Q1: Metanil yellow changes the colour of solution of dal to
(a) green
(b) pink
(c) blue
(d) dark red

Q2: Adulterated Arhar dal seems to be plain yellow because of the adulterant

(a) turmeric
(b) saffron
(c) metanil yellow
(d) basic yellow


Q3: To check the adulteration properly,dal is cooked with metanil yellow and ____is added.

(a) conc. HCl
(b) Conc. H2SO4
(c) Iodine sol.
(d) HNO3


Q4: Metanil yellow is basically:

(a) A base used to cook some foods.
(b) An acid used to neutralize base
(c) A chemical used in detergents.
(d) An inorganic dye used in leather,paper and textile industry.


Q5: Four students A,B,C and D carried out a test for the adulteration of metanil yellow in arhar dal and recorded their observations as given below. The procedure followed correctly is by the student____. The procedures were

STUDENT        PROCEDURE        OBSERVATION        INFERENCE
A        5 g dal+ 5g metanilDal turns yellowMetanil Yellow present
B        5 g dal+ 5 ml water+
2drops of HCl
solution turns pink/magentaMetanil yellow present
C        5 g dal+ 5 ml water+
pinch of Metanil yellow
Water turns yellowMetanil yellow present
D         5 g dal+ 5 ml water+
2 drops HCl
Water turns yellow
and then pink
Metanil yellow absent


(a) A
(b) B
(c) C
(d) D



Q6: Deepak washed a few grains of tur dal in water. The water became yellow.He then added a few drops of  HCl to the same test tube, the water turned pink in colour. From the above test Deepak concluded that tur dal contains:

(a) proteins
(b) starch
(c) turmeric
(d) metanil yellow


Learn about Preventing Food Adulteration



Answers:

 1) (b) pink
 2) (c) metanil yellow
 3) (a) conc. HCl
 4) (d) An inorganic dye used in leather,paper and textile industry.
 5) (b) B
 6) (d) metanil yellow

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