An Experiment Testing for Carbohydrates Non-Reducing sugars

Authors Avatar

Simone Davis-Weekes

An Experiment Testing for Carbohydrates Non-Reducing sugars

28 September 2001

Aim

To test for non-reducing sugars in 4 known substances and 1 unknown substance using Benedict’s reagent and Hydrochloric acid neutralised with Sodium Hydrogen Carbonate.

 Introduction

Benedict's test uses copper (II) sulphate.  This reagent is used as a general test for detecting reducing sugars. If the saccharide is a reducing sugar, it will reduce the copper (II) ions to copper (I) oxide, and form a red precipitate.  However, some saccharides need to be split and neutralised in order to detect their reducing sugars.

Risks 

Hydrochloric acid is very poisonous and corrosive if spilt wash affected area immediately.

Apparatus and Materials

Boiling tubes x 15, Pestle and mortar, Water bath, Stop clock, Permanent Marker, 8 pipettes 10cm³, 9cm³ 0.1% Glucose, 9cm³ 0.1% Sucrose, 9cm³ Unknown solution, 1g Grass, 1g Molasses, Litmus Paper, 20cm³ Water, 3cm³ Dilute Hydrochloric acid, 75cm³ Benedict’s Reagent, 9 drops Sucrase enzyme.  

Method

The following tubes were prepared and labelled

1a 3cm³ 0.1% Glucose and 5cm³ Benedict’s reagent were pipetted into a boiling tube.  The boiling tube was placed in a water bath for 8 minutes.  They were then removed and cooled.  The colour was recorded.

Join now!

1b 3cm³ 0.1% Glucose and 1cm³ Dilute Hydrochloric acid were pipetted into a boiling tube.  The boiling tube was placed in the water bath until the solution had boiled for 2 minutes.  The boiling tube was then removed and allowed to cool.  The solution was then neutralised using Sodium Hydrogen Carbonate.  Note: Enough of the Sodium Hydrogen Bicarbonate was used to stop the solution effervescing. Neutralisation was checked using Litmus paper.  Another 5cm³ Benedict’s reagent was added and the boiling tube was replaced in the water bath for 8 minutes.  The boiling tube was then removed, allowed to cool ...

This is a preview of the whole essay