The graph on the left illustrates the initial rate method for the formation of product. How About Make It Original? Exam revision summaries and references to science course specifications are unofficial. From runs i and ii , keeping [B] constant, by doubling [A], the rate is doubled, so 1st order with respect to reactant A. Wherever you draw a straight line, the data does not express itself as a linear plot and cannot be a 2nd order reaction. From runs ii and iii. I’ve made the numbers quite simple to follow the logic of the argument.

We will write a custom essay sample on Iodine Clock Reaction: The stirring motion was not kept constant and affects the time it takes for the potassium iodide to react with sodium thiosulphate as the rate of reaction would increase when the swirling motion is quick. Place the beaker containing the mixture 1 on the white tile. From runs i and ii , keeping [B] constant, by doubling [A], the rate is unchanged, so zero order with respect to reactant A. Repeat steps 2 to 4 with each of the remaining solutions Note: Give a valid conclusion to this experiment with an explanation. The aim of this experiment is to find the effect of varying the concentration of iodide ions on the rate of reaction between hydrogen peroxide and an acidified solution of potassium iodide.

A non-linear graph of concentration versus time would suggest first or second order kinetics. The third graph is a plot of HI decomposition rate versus [HI] squared, and, proved to linear reactio the blue data line was pretty coincident with a black ‘best straight line’.

Using syringes make up the following mixtures in five dry cm3 beakers. The initial rate is recation as the positive tangent – gradient for the curve at the point 0,0. Powers of 1 are not shown by mathematical convention. Both the sulfuric acid and hydrogen peroxide solutions irritate the eyes.

Its not a bad idea to repeat the calculation with another set of data as a double check! Example of a rate expression. We can now examine theoretically, the effect of changing individual concentrations on the rate of reaction of a more complicated rate expression of the form.

If any chemical splashes on your skin, wash it off immediately.

Iodine Clock Reaction – GCSE Science – Marked by

This proved to be a curve – compare the blue rate data curve reactiin the black ‘best straight line’ courtesy of Excel! The table below gives some initial data for the reaction: These example calculations below are based on the initial rate of reaction analysis – so we are assuming the variation of concentration with time for each experimental run has been processed in some way e.

The rate of radioactive decay is an example of 1st order kinetics. How About Make It Original?

The initial rate is based on the tangent from the 0,0 origin, over the first few minutes? Solutions Keep the temperature of the room constant by turning of the aircon before the lab starts, and checking coursewokr room temperature as the lab is being done 1 BBC GCSE Bitesize: Rsaction the order with respect to A is 2 or 2nd order.

Stirring Swirling motion Keep constant of the stirring motion, by using a magnetic stirring rod when the potassium iodide is added so it does not affect the rate of reaction. Examples of obtaining rate data.

Iodine Clock Reaction: Concentration Effect Essay

As seen in the graph there is a positive correlation between the volume Concentration of the potassium iodide and the rate or reaction. A small and constant amount of sodium thiosulfate and starch solution is added to the reaction mixture. I’ve also shown how to calculate the rate constant.

This proved that the decomposition of hydrogen iodide reaction is a 2nd order reaction. Starch- Indicator When starch is left in mixture for a long period of time, it starts to degrade and will take longer for the reaction to be seen affect the time taken.

From experimental results you need to know how the speed of a reaction varies with respect to individual reactant concentrations. During the lab, the temperature of the room increased resulting in a faster reaction changing the correlation between the rate c,ock reaction and the volume usage.

The concentration of iodide, peroxodisulfate or an added catalyst e. Eric from Graduateway Hi there, would you like to get an essay? The idea is that somehow you test for the order ioddine an appropriate linear graph From the point of teaction of coursework projects the detailed analysis described above is required, but quite often in examination questions a very limited amount of data is given and some clear logical thinking is required.

The Iodine Clock Investigation

In the zero order graph the gradient is constant reactiob the rate is independent of concentration, so the graph is of a linear descent in concentration of reactant. From runs i and iikeeping [B] constant, by doubling [A], the rate is unchanged, so zero order with respect to reactant A.

Only then is it possible to derive a rate expressionwhich summarises what controls the speed of a particular reaction in terms of the relevant concentrationswhich is not necessarily ikdine the reactants!

Therefore the reaction is 1st order overalland the rate expression is Add it to mixture 1 as quickly as possible and at the same time start the timer. In reality the results would be not this perfect and you would calculate k for each set of results and quote the average!