Determining the Effect of Different Sugar Concentrations on Benedict's Solution

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Determining the Effect of Different Sugar Concentrations on Benedict's Solution

PLANNING:

Hypothesis and prediction:

My hypothesis is that the sugar solution with the highest

concentration will turn the precipitate the darkest colour. This will

be the 10% sugar solution. This is because the more amount of sugar it

contains the more it will reduce the Copper. It will be a much darker

precipitate compared to the other two.

Background theory:

Benedict's solution is an aqueous solution of Copper (II) Sulphate,

Sodium carbonate and Sodium citrate. It is an alkaline solution used

to test for the presence of aldehyde groups (RCHO). The reducing sugar

(Glucose) reduces the copper (II) Sulphate to Copper (I) oxide. The

colour of the precipitate varies dependent on the strength of the

reducing sugar present. The colour can vary from blue to red-brick:

indicating a high concentration of sugar. Glucose contains an aldehyde

group, so it is able to reduce the Benedict's solution and form a

precipitate. An aldehyde contains the general formula; RCHO, where the

R represents Hydrogen. They are formed from partial oxidation of

primary alcohols. An aldeyde is formed due to cabonyl groups; these

contain an Oxygen atom joined by a double bond to carbon. If the

carbonyl is joined to a hydrogen atom, then the compound is an

aldehyde. Glucose is a monosaccharide. Monosaccharides can take the

form of linear or ring structures. The carbonyl on the carbon 1

supplies the electron which joins the carbon 1 to carbon 5. When this

bond breaks, there are extra electrons which are then used to reduce

other molecules. The heating thus breaks these bonds, so then the free

electrons reduce the Copper (II) Sulphate to Copper (I) oxide in the

Benedict's solution. The reason why the Benedict's solution is readily

reduced is because it has a high PH, hence alkaline, whereas the

Carboxyl group in the Glucose gives it acidic properties. It splits

open the ring structure, consequently releasing the electrons which

are accepted by the Copper. The Copper (II) ions act as a mild

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