NAME: Michael TimsonDATE: 9/10/2004FORM: L6-4LAB: #2SUBJECT: BiologyTEACHERS NAME: Miss SarjeantTOPIC: Biochemistry (Quantitative food test)AIM: To estimate the glucose concentration of 3 unknown glucose solutions.

INTRODUCTION:Quantitative analysis is a branch in chemistry that relates to the determination of the amount or percentage of one or more constituents of a sample. A variety of methods is employed for quantitative analyses and can be broadcast into two groups; chemical or physical. This depends upon which properties of the sample are utilized. Chemical methods depend upon such reactions as precipitation, neutralization, oxidation, or, in general, the formation of a new compound. The major types of strictly chemical methods are known asgravimetric and titrimetric analysis. Titrimetric analysis volumetrically measures the amount of reagent or concentration, called a titrant, required to complete a chemical reaction with the analyte. A generic chemical reaction for titrimetric analysis is: aA + tT products, whereamole of analyte,A,contained in the sample reacts withtmoles of the titrant,T.in the titrant solution. This reaction is carried out containing the liquid or dissolved sample. Titrant solution is volumetrically delivered to the reaction flask using a burette. Delivery of the titrant is called a titration. The titration is complete when sufficient titrant has been added to react with all the analyte. This is called theequivalence point. An indicator is often added to the reaction to indicate when all of the analyte has reacted. The titrant volume where the signal is generated is called theend point. Carbohydrates (hydrated carbon) are organic compounds. Their molecules contain carbon together with hydrogen and oxygen and have a general formula Cx(H2O)y. There are three groups of carbohydrates. These groups are monosaccharaides, disaccharides and polysaccharides. Glucose is acarbohydrate, and is the most important simplesugarin human metabolism. Glucose is monosaccharide because it is one of the smallest units which have the characteristics of this class of carbohydrates. Glucose, like all other monosaccharides, is classified as reducing sugars. It readily reduces other chemicals found in the solution. Monosaccharides are classed into three groups. These groups are classified according to their number of atoms and the arrangement of atoms. They are trioses, pentose and hexose. Hexose such as glucose form the main source of energy for a living organism and when broken down during respiration, releases chemical energy trapped within the glucose molecule.

APPARATUS/MATERIALS: 3 Syringes 2 Boiling Tubes

Potassium Permanganate Sulphuric Acid

Stopwatch 2% Glucose

4% Glucose 6% Glucose

10% Glucose 8% Glucose

Solution A 12% Glucose

Solution B Solution C

METHOD:Three syringes were labelled G, S and P. Two boiling tubes were labelled 2% which indicated the concentration of glucose used. 10cm3 of 2% glucose solution was place in each boiling tube. 5 cm3 of sulphuric acid was added. 2cm3 of potassium permanganate was then added to each boiling tube and the timer was then started. The solution was then stirred in the boiling tube text to a white paper and observed when the pink colour disappeared. The stopwatch was then stopped and the time was then recorded when the solution turned clear. Steps 4 6 were then repeated. Steps 2-7 were repeated for each glucose solution. The results were then tabulated and a time vs concentration graph and a rate vs concentration graph were then plotted.RESULTS:TABLE SHOWING THE TIME TAKEN FOR ALL THE GLUCOSE TO REACT FOR EACH CONCENTRATION LEVEL OF GLUCOSEConcentration of glucose / %Time taken to decolourize / secondsRate of reaction / 1/t

1st 2nd Average

22972982980.003

41801781790.006

61151151150.009

88690880.011

107171710.014

126364640.017

TABLE TWO SHOWING THE THREE UNKNOWN GLUCOSE SOLUTIONS AND THE TIME TAKEN TO DECOLOURIZESolutionTime taken to decolourize / seconds

1st 2nd Average

A240238239

B125125125

C108107108

DISCUSSION: Glucose (C6H12O6) is a monosaccharide reducing sugar. In this reaction the glucose readily donates electrons which are accepted by the permanganate causing it to change colour. The purple pink solution of potassium permanganate (MnO4) is reduced to a colourless solution of manganese ions (Mn2+).MnO4- + 8H+ + 5e- Mn2+ + 4H2O Purple pink in solution colourless in solutionAs a result of this reaction the glucose is oxidised.The time taken for the loss of colour from a standardised solution of permanganate is directly related to the concentration of glucose present in solutionFrom table one above, a graph of concentration of glucose vs time was plotted followed by a graph of rate of reaction (1/t) vs concentration (%). From the graph of concentration of glucose vs time, the concentrations of solution A, B and C was then determined. According to the graph obtained from the results of this experiment, the concentration of A, B and C was 2.8%, 5.6% and 6.4% respectively. From this result, the rate of reaction for these three solutions was then determined using the graph of rate of reaction vs concentration. Based on these results, the rate of reaction of solutions A, B and C was 0.004, 0.008 and 0.0092 respectively. From the first graph, it was seen that as concentration of glucose increased, the time taken to complete the reaction decreased. From concentrations 2-6, there was a rapid decrease in time whereas for concentrations 6-12, there was a gradual decrease.in time for the reaction to take place. This first graph thus indicates that the time taken for reaction is thus dependent on the concentration of glucose present in the solution. From the second graph, a straight line was obtained when indicates that the rate of reaction was directly proportional to the concentration of glucose present. This thus means that as the concentration increased, the rate of reaction increased proportionally with a gradient of 0.0014.From these two graphs, it is observed that the rate of reaction is faster with a higher concentration of glucose than a lower concentration of glucose. This is a result of more molecules of glucose present in the solution and thus the number of collisions will increase causing the rate of reaction increase.

CONCLUSION: Based on the results obtained from this experiment, the concentration of solution A, B and C was 2.8%, 5.6% and 6.4% respectively.