identifying mystery substances

Question 1

what 5 tests do you carry out and what do they test for?

Answer 1

-biurets-protein
-benedicts-reducing sugar
-ethanol- lipids
-iodine-starch
-benedicts and acid hydrolysis-non reducing sugars

Question 2

colour change for iodine

Answer 2

-orange brown
-blue black

Question 3

colour change for lipids

Answer 3

-clear
-cloudy emulsion

Question 4

colour change for biurets

Answer 4

-blue
-purple/lilac

Question 5

colour change for benedicts

Answer 5

-blue
-green/red or brick red precipitate

Question 6

how to do iodine test for starch

Answer 6

-add 1cm^3 of sample to spotting tile
-add a few drops of iodine

Question 7

how to do emulsion test for lipids

Answer 7

-add 1cm^3 of ethanol to test tube
-add 1cm^3 of sample
-shake
-add 1cm^3 of cold water

Question 8

how to do biurets test for protein

Answer 8

-add 2cm^3 sample solution to test tube
-add 2cm%3 of Biurets

Question 9

how to do benedicts test for reducing sugars

Answer 9

-add 2cm^3 of sample solution to test tube
-add 2cm^3 of Benedicts reagent
-heat in 85 degrees water bath for 2 mins
-

Question 10

how to do acid hydrolysis of non reducing sugars

Answer 10

-add 2cm^3 of sample solution to test tube
-add 1cm^3 of 1m HCL
-boil in water bath for 1 min
-carefully neutralise with NaHCO3 powder
-check pH with indicator paper
-carry out Benedicts Test

Question 11

how would you test the relationship of glucose concentration and sweetness?

Answer 11

-colorimeter
-taste for sweetness, however this is subjective