• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

To find out the effect of varying concentration of potassium iodide in a I2 / H2O2 reaction

Extracts from this document...


LAB REPORT - KINETICS Effect of Concentration (I2 / H2O2 reaction) Aim To find out the effect of varying concentration of potassium iodide in a I2 / H2O2 reaction on its reaction rate Hypothesis In this reaction between hydrogen peroxide and potassium iodide, the amount of hydrogen peroxide is kept constant while the amount of potassium iodide is changed. There are two stages that happen in this reaction. In the above reaction, hydrogen peroxide is broken down into water molecules. The iodine ions from potassium iodide are converted into iodine molecules. When sodium thiosulphate reacts with starch and uses it up, it starts reacting with iodine molecules instead, converting them back into iodine ions. Therefore the iodine ions are not used up in the reaction until all the sodium thiosulphate reacts. However, the excess iodine molecules cannot be converted back into iodide ions and react with starch instead to produce a blue colour. I predict that when the solution turns blue, the reaction has finished. An excess of acid is present in the reaction mixture so that the decrease in the acidity caused by reaction (1) ...read more.


water 30 35 40 45 50 measuring cylinder 5. 0.1M Na2S2O3 10 10 10 10 10 pipette 6. '2 volume' H2O2 20 20 20 20 20 pipette Total volume 145 145 145 145 145 (3) Take the measured chemicals 1 and 2 in a beaker, 3 and 4 in another separate one, and 5 and 6 in yet another beaker (4) First mix chemicals 1 and 2, and 3 and 4, into a conical flask. (5) Then mix the 5 and 6 into the solution and immediately start the stopwatch. Swirl the solution only once and record the time it takes for the solution to turn blue. (6) Repeat the experiment, taking other values for volumes, such as in Expt A to E. Data Presentation Experiment Volume of KI/cm3 � 0.05 cm3 Time/s � 0.5s A 25 51.06 B 20 60.03 C 15 74.00 D 10 87.63 E 5 110.26 Data Processing There were a few uncertainties in the equipment that we used. At first, the systematic and random error values must be calculated. The uncertainties were given on each of the measuring instruments that we used. ...read more.


Error in measurement: Percentage error (%) = 3.20% Therefore, 3.20% of 0.0222 � 0.0007 Therefore the rate constant = 0.0222 � 0.0007 Literature value = 0.018 Therefore, total error = Conclusion By plotting a graph of volume against time, we can find the half-life of the reaction. The graph was found to be a curve with a constant half-life. This indicated that the reaction was a first-order reaction. The error in this reading can be caused mainly by human errors in taking readings or using wrong methods - example, it could be difficult to time the reaction properly. Taking an average is a good way to reduce this error. By plotting a graph of rate against concentration, the rate constant k was found to be about 0.0222. Here also the error in measuring time would give wrong readings of the rate constant. The percentage systematic error was found to be quite small. There could have been an error in calculating the percentage error. However, the error between the experimental and literature values is very large: 23%. Even the error bars of the systematic error of 0.0007 do not compensate for the error. This could be due to faulty equipment. * For further experiments, investigate the effects of performing the experiment at different temperatures. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Patterns of Behaviour essays

  1. Rates of Reaction - The Iodine Clock

    24 261 81 RESULTS: 1 2 3 4 5 6 Volume (ml) H2O 161 159 157 155 153 151 Na2S2O3 8 8 8 8 8 8 KI 10 10 10 10 10 10 H2O2 10 10 10 10 10 10 H2SO4 10 12 14 16 18 20 Starch 1 1 1 1 1 1 Time (seconds)

  2. The Decomposition of H2O2 using Catalase, in yeast as a catalyst.

    So then I decided to try the experiment at 20?C and not include 10?C in my range. Pre-test 4 * 0.1g yeast used * 10cm3 of H2O2 * This experiment was carried out at 20?C Time (minutes) Volume of O2 (cm3)

  1. The Effect of Catalase in the Breakdown of Hydrogen Peroxide

    In addition; by looking at the peeled potato's graph, one can see that the both concentrations of the catalase had not completed its reaction. This was because; the reaction proved to be exceptionally slow in comparison to the unpeeled. The unpeeled potato proved to be fast, especially when 80% of the catalase was used.

  2. Activity of Diastase On Starch

    starch breakdown, you are also increasing the chances of the breakdown of the three-dimensional structure of the enzyme. As the heat in the system increases, the vibrational energy of the entire distase molecule also increases. This puts a strain on the weak interactions that hold the enzyme together.

  1. To investigate the effect of changing concentration of Hydrogen Peroxide (H2O2) on the enzyme ...

    Equipment chosen Reason for equipment Stop clock To make an accurate experiment of 3 minutes. Large measuring cylinder The small cylinder was too small, so the big one was used. Beaker To hold the water Conical flask It was used to give the substrate a large surface area.

  2. To determine the rate law for a chemical reaction among hydrogen peroxide, iodide and ...

    --- (I) I3- (aq) + 2 S2O32- (aq) � 3 I- (aq) + S4O62- (aq) --- (II) 2 I3- (aq) + starch � starch-I5-complex + I- (aq) --- (III) The first equation indicates that, in an acidic solution, iodide ions were oxidized by hydrogen peroxide to triiodide ions.

  1. To investigate the effect of varying the masses of white sugar and yeast and ...

    Because of this easy absorption, these sugars are the first ones used in the fermentation process. Their consumption takes place during the first 30 minutes or so at the beginning of the fermentation process. Complex sugars: The two main types naturally present in flour, saccharose and maltose, represent approximately 1% of the flour.

  2. Investigating the effect of enzyme concentration on the hydrolysis of starch with amylase.

    concentration of enzyme in % The graph reflects my prediction that as the concentration increases, the time taken for the rate of reaction increases, as it takes less time for a reaction to occur The exact relationship between the rate of reaction is dependant on the reaction 'mechanism'.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work