Tests

Question 1

Describe the test for starch

Answer 1

🔥add drops of iodine to unknown solution in a test
🔥shake / stir
🔥Blue black indicates presence of starch.

Question 2

Describe the test for a reducing sugar

Answer 2

🍐Add benedicts reagent to unknown solution
🍐a yellow green orange red ppt indicates presence of a reducing sugar
🍐if solution remains blue then no reducing sugar is present

Question 3

Describe the test for non reducing sugars

Answer 3

🌸First perform a benedicts test to show reducing sugars are not present
🌸then add sample to hydrochloric acid (dilute)
Bring mixture to boiling point
Cool it
🌸add dilute sodium hydrogen-carbonate solution to neutralize the acid
🌸add Benedict reagent to solution
🌸place in water bath
🌸if orange or red ppt
🌸if solution remains blue then it’s not a reducing or non reducing sugar

Question 4

Describe the test for protein

Answer 4

🥀Add sodium hydroxide (dilute) to solution
🥀add a few drops of dilute copper sulphate and mix gently
🥀if protein is present then a lilac color will show and this is because the copper ions in the copper sulphate react with peptide bonds in the protein