CHEM IA HELP NEEDED ASAP THANK YOU!

[Mao]

Hi everyone,

I have my chemistry coming up really soon, and have a burning question to ask! Thank you so much for your help in advance.

My aim is to measure the reaction rate of a reaction, to see the relationship between reaction rate and reactant concentration.

I thought about two methods, and I would like to ask if they will work, and which one is better.

1)  Do the reaction 2HCl(aq)+Mg(s)→MgCl₂(s)+H₂(g) and measure the mass of the reactants at the beginning, and after a set period of time. (then calculate the reaction rate). I will change the concentration of the HCl every time.

2) Do the reaction between sodium thiosulfate and hydrochloric acid to make Sulfur, and measure the time it takes until a cross at the bottom of the beaker cannot be seen.

Are these methods going to work? Will I be able to get accurate and precise results? Is there a better and more accurate method?

Thank you so much!!!!!!!!!!!!

[kw0573]

Generally, the Arrhenius equation is to find instaneous rate, not over a period time. At least pick a quantity that you can measure at least once every second then you can calculate initial rate (or average rate over a very short period of time).

In general, rate experiments are easy to do but hard to analyze. There are also lots that can be said about ereor analysis. Basically if initial rate varies rapidly just pick make the reactants more dilute. Changing temperature also works as temperature effecta are more evident and you dont have to reprepare solutions.

Finally if you are not applying Arrhenius equation, the analysis is generally not very sophisticated and may lose few marks. 

For your 2-bromoethane post, you can try synthesizing from ethene (bromination of alkene), or from photocatalyzed halogenation of alkane. You can use longer chains such as 5-6 carbons to synthesize reactants (starting materials) which may be more available and much safer.