Okay so now you have made all of your measurements over the number of minutes. I am providing you here with some extra data as if we had continued the reaction for some longer period of time. This is necessary in order to make the distinction between the different orders reaction. So, if you had carried on the experiment for a longer period of time right out to around about half an hour, then the volumes of gas which would have been evolved are given here. So, if you'd like to take this set of data here and just add it to your set of data in order to have a complete set of data. You can see at the bottom I've also added on a, value for what I've called infinite time. This is whereby the reaction has been driven to completion. This is done by actually warming up the reaction in order to drive it to completion then re-equiliberating it at 35 degrees centigrade and taking an evolved volume of gas. And you can see that the infinite reading time, time T equals infinity. Is an evolution of 35.1 centimetre cubed of oxygen. So take all this data and add it to your data set and then will be ready to do the analysis. Ok, so we have all our data, now we need to analyze it. Here's the reaction which we've been looking at. The decomposition of hydrogen peroxide. Now, we go back to some of our first lectures, we can write out a rate for this process in terms of the decomposition or the disappearance if you like of the hydrogen peroxide so the rate is minus. Because its disappearing the rate of change of concentration of hydrogen peroxide with time. Now we don't know the order of this reaction. It will be therefore equal to some rate constant. Times the concentration of hydrogen peroxide. To some power. Which will be the order with respect to hydrogen peroxide. It will also be relying on the amount of iodide which we had in this catalyst raised to some power. However the iodide concentration itself is going to be a constant for any particular reaction that we do because it acts as a catalyst. My, I could have added more hydrogen iodide, and then I'd get a different rate, but for the, the actual experiment that we did, the iodide concentration will be constant. Therefore if this here is constant we can take this term here into the rate constant k. And then we have a new expression whereby the greater change of concentration of hydrogen peroxide with time is now equal to an apparent rate constant k times the concentration of hydrogen peroxide raised to sum power n which is the order with the reaction. Now, if we want to determine the order of the reaction we have to, make some relevant plots. And if their a straight line, then we'll be able to determine the order of the reactions. So we just remind ourselves what we would have to do. Let's suppose the reaction was zero order, then the relevent plot will be just plotting the concentration hydrogen peroxide versus time. If it's first order we need to plot the natural log of the hy, hydrogen peroxide concentration versus time. And if it's the second order we need to plot one over the concentration versus time. And if we do that, we will get a slope, if it's a straight line and therefore intercept as well. If it works out for zero order, the slope will be minus the zero order rate constant. And the intercept will be the initial concentration in this case hydrogen peroxide. This slope will be the same if its first order [UNKNOWN] first order rate constant the intercept will be logarithm of the initial concentration. And if it's the second [UNKNOWN] plot the slope will be positive the urate constant, second [UNKNOWN] constant. And the intercept will be one over the initial concentration. This case of the hydrogen peroxide. Now we're not measuring the concentration of hydrogen peroxide as a function of time. We're measuring the volume of evolved oxygen gas. And therefore we need to understand how one is related to the other. So, if we think about the reactions it proceeds the hydrogen peroxide is reacting. And the amount that reacts will be directly proportional to the volume V of oxygen released. So the longer it reacts, the more oxygen is released. The larger V becomes. If you go right to the end of the process when everything has reacted we get finally a final value. This is what I call the value at T infinity. And the, when everything has reacted this total volume gas must be proportional. To the initial amount of hydrogen peroxide that we had at the beginning. because now everything is being converted into water and oxygen. And we get this final volume of gas released. So we don't want either of these two things. We don't want the amount reacted, and we don't want the initial amount. What we want is the amount of hydrogenpPeroxide at any given time 't', well we can get that because we just need to take amount that we start with minus the amount that is reacted and that will give you amount that you have at any particular time 't'. So we can get at least a proportionality rather easily because. This is proportional to the final and this is proportional to v. So the whole thing would be proportional to v final minus v. We can also work out the constant of proportionality because we know that the hydrogen peroxide concentration at the end is proportional to the final volume V given out. And therefore the hydrogen peroxide concentration is equal to some constant. Constant of proportionality times V final. Now, we know V final because it was that, the last value in the tables I gave you of infinite time. So, that was 35.1 centimeters cubed. Consequently we know this. If we know these starting concentration of hydrogen peroxide, we know that because we know what the concentration was at the beginning. So I'll give that you now, the concentration at the beginning of the experiment was 0.892 moles per liter of hydrogen peroxide. That's after the dilution with potassium iodine. So if you use this value here and this value here, you should be able to determine a constant of proportionality. Okay so now we have all the tools to get going. So what you need to do at this point is you need to make some plots. So you need to make zero order plot way of plotting the concentration versus time so your concentration will be this consular proportionality which you'll have to determine times v final minus minus v. If you want the first order plot you'll need to plot the natural log of the same thing. You want to do a second order plot, you will need to do one over the same thing. They call these plots with these, on the Y axis, and your time on the X axis. And then from that you should be able to determine the order of reaction by just seeing which of those plots is a straight line. When you found the straight line plot, you used the straight line in order to determine the slope and thereby get the rate constant. So if you go away now you can use an Excel spreadsheet or any other method in order to do the analysis. After you've done that, you can enter the order that you obtain and the rate constant you obtain. Let's see if you get them right, and after that, I'll show you how the calculations should've been done and the numbers that you should have got from the experiment. [BLANK_AUDIO]