If you want to test a sample to see if glucose is present wh

If you want to test a sample to see if glucose is present, what reagent should you use? If amylase is added to a sample of potato and you test it with Benedict\'s reagent 10 minutes later, what do you expect the results of the test to be? Justify your reply. After enjoying a meal of fish and chips, you notice your shirt has an oily stain on it. Why won\'t the oily stain come out when you dab at it with just water? If the sample of water you test with biuret reagent turns purple, what should you conclude about the results of your experiment? Explain.

Solution

14.

Benedicts or fehling’s reagent is used to test for glucose. The test involves heating the sugar and chemicals are added and by this colour change observed is blue or orange.

15.

If amylase is added to the sample of potato and it is tested with the benedicts reagent with 10 minutes and later we can observe colour change from blue to green, brick red ,yellow or orange.

Amylase is an enzyme that turns the starch into sugars and the get reacted with benedicts reagent and we can observe the colour change.

16.

Oily stains won’t remove when we dab even with water because Oily stains generally contains the fatty acids and these have low density than water and they are insoluble in water , soft and low melting solids.

Fats contains the fatty acids that combined with glycerol.

17.

If a sample of water is tested with biuret reagent and if we observe the colour change of solution to purple then we can say that contains the proteins.

If aqueous sample is treated with equal volume of 1% strong base and to this few drops of aqueous copper sulphate is added then we can observe purple colour change in the solution , by this we can confirm the presence of proteins.