Rates Of Reaction Between Sodium Thiosulphate And Hydrochloric Acid Coursework Examples Of Rhetorical Analysis Essay
You can then plot 1/t as a measure of rate against the varying concentrations of the reactant you are investigating.
If the reaction is first order with respect to that substance, then you would get a straight line.
You could also use a special flask with a divided bottom, with the catalyst in one side, and the hydrogen peroxide solution in the other. If you use a 10 cm measuring cylinder, initially full of water, you can reasonably accurately record the time taken to collect a small fixed volume of gas.
You could, of course, use a small gas syringe instead.
If you plotted the volume of gas given off against time, you would probably get the first graph below.That is only a reasonable approximation if you are considering a very early stage in the reaction.The further into the reaction you go, the more the graph will start to curve.This is repeated for a range of concentrations of the substance you are interested in.You would need to cover a reasonably wide range of concentrations, taking perhaps 5 or so different concentrations varying from the original one down to half of it or less.The maths goes like this: If you have a reaction involving A, with an order of n with respect to A, the rate equation says: If you plotted log(rate) agains log[A], this second equation would plot as a straight line with slope n.If you measure the slope of this line, you get the order of the reaction. Note: Don't worry if you don't understand logs (logarithms), or how I got from the first equation to the second one!If you look at the expressions in the table above, you should recognise that the initial rate is inversely proportional to the time taken.In symbols: In experiments of this sort, you often just use 1/t as a measure of the initial rate without any further calculations.Since this is the part of the reaction you are most interested in, introducing errors here would be stupid!You have to find a way of adding the catalyst to the hydrogen peroxide solution without changing the volume of gas collected.