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# Sodium thiosulphate and order of reaction watch

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1. I recently did the reaction between Sodium thiosulphate and hydrochloric acid , varying both concentration to find the order of the reaction. The answer got contradicts some others I've found. Could anyine please tell me what the order is?
2. The order of reaction varies depending on the concentration of the acid and can be anywhere between zero and first.
3. Thanks alot Markkey!
4. Could someone explain how the order of this reaction changes with the concentration of the acid? Does the slow-step change? And if so, is the change discrete?
5. the order of the reaction usually depends on the slow step right? because that's the rate determining step.

if this is for edexel, you usually have a table of values for the rate or time with the conc of reagents, if the rate doubles when the conc of one of the reagent doubles the order for that reagent is 1

if the conc doubles but the rate quadruples the order of that reagent is 2

if there's no change inthe rate for the doubling of the conc of a reagent, the order of the reaction is 0

adding all the orders in a reaction will give you the overall rate

does that help at all? (hope im not telling you what you already know lol)
6. Thanks for the help b33jal, but that's not really what i'm asking (and the question isn't edexcel).

I initially wanted to know the order of reaction of the equation between Na2S203 and HCl. I conducted this experiment at a HCL concentration of ~0.5M. This provided me with the order of reaction with respect to HCL being zero. I reconducted this experiment with HCL conc at 2M. This lead to an order of 2 (with respect to HCL). Markkey about also commented on the variance of order with concentration. I wish to know how the concentration changes the order of the reaction (with HCL)?
7. we got told it didnt matter wat your experiment showed...if it was wrong it didnt matter cos youve just got 2 manuipulate the results you got.
8. As far as I have read around, the order w.r.t. sodium thiosulphate is 1. The order w.r.t. Hcl seems to vary. I first obtained 0, then 2 (with a much higher conc. of HCl). I just want to know how order changes with concentration.
9. Anyone?! :heeeellll

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Updated: April 19, 2006
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