Introduction:
The purple pink solution of potassium permanganate (MnO4 -) is reduced by glucose to a colourless solution of manganese ions (Mn2+). MnO4- + 8H+ + 5e- Mn2+ + 4H2O
The time taken for the loss of colour from a standardised solution of permanganate is directly related to the concentration of glucose present in solution.
Research question:
How does the different concentration of glucose solution which have the same volume affects the time taken for the pink color of the potassium permanganate to turn into colorless?
Hypothesis:
The higher the concentration of glucose, the shorter time taken for the reduction of potassium permanganate, hence resulting in shorter time taken for the pink color of potassium permanganate to decolorize. This is because the concentration of glucose molecules in glucose solution is high thus more electron are donated to the permanganate within a constant period.
Variables:
•Independent: The concentration of the glucose solution
•Dependent: The time taken for the pink color of the potassium permanganate to turn into colorless •Controlled: Volume/Units
Materials list :
•Eye protection
•A timer
•a glass rod
•a boiling tube and a rack
•3 beakers
•3 syringes
•6 labels
•glucose solutions (2%,4%,6%,8%,10%,12%)
•3 solution of unknown glucose concentration (A,B,C)
•sulphuric acid
•potassium permanganate
Procedure:
1.label your three beakers sulphuric acid
PP- for potassium permanganate
G- for glucose
2.label your syringes in the same way.
3.add about 25 cm3 of sulphuric acid and potassium permanganate to the beakers – this will be your stock to use throughout the experiment. note which glucose solution you are testing first. 4.use the correct syringe to place 10 cm3 of the first glucose solution into the boiling tube. 5.add 5 cm3 of sulphuric acid.
6.add 2 cm3 of potassium permanganate and start the clock.
7.stir with a stirring rod and stop the clock as soon as the pink color disappears. 8.record the time and the glucose solution used.
9.rinse the syringe you used for the glucose solution.
10.repeat using the other glucose solution.
11.repeat for a solution of unknown concentration (A B or C) 12.record your own results and if possible class average results in a table.
Table:
Glucose concentrationsTime taken to change color
2%1 minute 41 seconds
4%1 minute 13 seconds
6%45 seconds
8%41 seconds
10%35 seconds
12%32 seconds
Unknown A48 seconds
Unknown B1 minute 13 seconds
Unknown C2 minute 56 seconds
Graph :
conclusion:
Evaluation:
sources of error=
•the temperature of the water was not the same with all the concentrations •minor inaccuracy in watching the exact time that the color changes absolutely •inaccuracy in using the stop watch
Reference:
https://www.google.com.bh/#hl=en&sclient=psy-ab&q=estimating+glucose+concentration+in+solution+lab+report+hypothesis&oq=estimating+glucose+concentration+in+solution+lab+report+hypothesis&gs_l=hp.3…3351.18905.1.19921.11.11.0.0.0.0.421.2839.2-10j0j1.11.0…0.0…1c.1.7.psy-ab.csPQdc8wzZA&pbx=1&bav=on.2,or.r_cp.r_qf.&bvm=bv.44011176,d.d2k&fp=34c3fbe89c60be0d&biw=1366&bih=629.