Hi

I am doing a lab report for the kinetic behaviour of phenolphthalein in aqueous solutions. I did two runs, each with different concentrations of OH-, and Cl-. I have graphed x, ln x, and 1/x to determine which one has the most linear plot to determine what order the reaction is, but for one run, I have determined that the reaction was first order and for the second run, I have determined that the reaction was second order.

My question is, is this possible? I'm not sure if first order should apply to both runs because it is essentially the same reaction, just with different concentrations.

Please advise.

Thanks

No, I don't think the reaction order can change under small changes.

Hello!

Determining the order of a reaction based on the concentration is an important step in the analysis of reaction kinetics. In your case, you mentioned doing two runs with different concentrations of OH- and Cl-. It is indeed possible to have different orders of reaction for different runs, even if it is the same reaction.

The order of a reaction describes how the rate of the reaction depends on the concentrations of the reactants. It is determined by analyzing the data and plotting graphs of concentration against time or ln(concentration) against time.

When you say you determined the reaction to be first order in one run and second order in the other, it suggests that the rate of the reaction is dependent on the concentration of reactants to different powers in each case.

It is common for the order of a reaction to change with varying reactant concentrations. This could be due to factors such as the mechanism of the reaction, the presence of additional reactants or catalysts, or changes in reaction conditions.

To be certain about your findings, it is important to have enough experimental data points and to perform a thorough analysis. It is also a good idea to consult your lab manual or your instructor, as they may have specific expectations for your experiment and the interpretation of the results.

In summary, it is possible for the order of a reaction to vary in different runs, even if it is the same reaction. This variation could be due to several factors, and it is crucial to analyze the experimental data carefully and seek guidance from reliable sources to ensure accurate conclusions.

I hope this explanation helps! If you have any more questions, feel free to ask.