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Investigating the rate of reaction between sodium thiosulphate and hydrochloric acid coursework

I have done the pratical work and found that the rection was first order with respect to the thio and both first and zero order with respect to the acid, depending on the concentration. Can anyone give me some help with the reaction mechanism as I cant come up with any ideas. Not what you're looking for? Report 10 years ago 2. Report Thread starter 10 years ago 3. Does anyone have any ideas about the reaction mechanism. There must be a rate determining step, but how does it all link together. Help much appreciated. Rubs Badges: 1. Report 10 years ago 4. The reaction which I've seen on a few websites, inc.

To demonstrate the concept of reaction rate in chemistry classes. The thiosulfate ion can decompose into the sulfite ion and a colloidal suspension of sulfur, which is opaque. Report Thread starter 10 years ago 5. Report 10 years ago 6. With HCl though this is the case initially, but like I said there comes a point where the step s involving HCl become so fast that increasing its concentration isn't going to make a difference.

At this point you have enough HCl to collide with the rectants, and the only thing that's holiding it up is the rate-determining step above. Oh and remember - frequency of collisions isn't the only factor to affect the rate of reaction, temperature is important. Molecules can collide as many times as they want, but if they don't have the correct activation energy to react they're not going to. Report Thread starter 10 years ago 7. Report Thread starter 10 years ago 8. Report 10 years ago 9.

Sorry I didn't make this bit clear! The concentration of acid does not affect this, this is only affected by the concentration of sodium thiosulphate see above. Report Thread starter 10 years ago Does anyone have any ideas? It is a homogeneous catalyst as the catalyst is in the same physical state as the reactants. Report 8 years ago Hey i just wanted to ask if u made the thiosulfate or whether you just ordered it like that? Hey i done this experiment and im a little confused with working out the rate determining step would this be correct : Step 1. Report 4 years ago I try to explain the order of reaction more like a relay race.

The intermediate steps run like a relay, one has to go before the other. Therefore the slowest runner the slowest step in the reaction mechanism will limit hence the term "rate limiting step" the speed that the whole relay team can run. No matter how fast the other runners are, they have to wait for the slow one and so it limits the overall speed and thus determines it, since most intermediate steps happen nearly instantaneously.


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In this mechanism, the slow step is the thiosulphate decomposing into sulphur and sulphate IV ion sulfite ion under the old naming rules. It is first order because one molecule of thiosulphate is involved.

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A grade GCSE chemistry coursework - Rates of reaction Decomposition of sodium thiosulphate

No acid is in step 1 of the above mechanism as you've shown. I am doing this experiment as well. How much of each catalyst did you use? Report 3 years ago Original post by rebeccabroadbent Hey i done this experiment and im a little confused with working out the rate determining step would this be correct : Step 1. Quick Reply. Submit reply. Attached files.

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Sodium Thiosulphate and Hydrochloric Acid Rate of reaction

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Investigating Reaction Rates of Sodium Thiosulphate and | Bartleby

This animation can be used to introduce the reaction between marble chips calcium carbonate and hydrochloric acid as a way of measuring the effect of surface on rate of reaction. The rate of this reaction can be changed by changing the size of the marble chips.


  1. SODIUM THIOSULPHATE AND HYDROCHLORIC ACID COURSEWORK CONCLUSION.
  2. Found what you're looking for?.
  3. Marble chips and hydrochloric acid coursework.
  4. When calcium carbonate is added to hydrochloric acid a reaction takes place. And hence, if we grind up the marble finely, more surface area is exposed, and thus its reaction with added HCl should be more facile. The calcium carbonate must be in excess in both test tubes.

    This is the method used. Because using smaller marble chips increases the surface area, meaning that more of the solid is exposed to the acid particles. Thus, the rate of reaction for calcium carbonate powder is higher. Measured 5ml of hydrochloric acid in the 10ml measuring cylinders and placed into each beaker separately. Materials: Marble chips, 2 mol dm-3 hydrochloric acid, 0. For our experiment we used 25ml of acid All of the concentrations used the same amount 0. Marble chips, also known as calcium carbonate is a chemical compound with the molecular formula CaCO3. What we want to be able to do here is to allow students to start investigating the reactions where they can change three of the factors-- temperature of solutions, the surface area of the solid, and the concentration of the 1.

    It shows crushed marble chips reacting with The smaller the chips, the bigger the surface area and the faster the reaction. IntroductionWe are going to do an experiment to see how surface area effects the rate of I will add calcium carbonate marble chips to hydrochloric acid.

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    However instead of investigating all four variables, I have chosen to investigate how different concentrations of hydrochloric acid affect the rate of reaction between marble chips and hydrochloric acid. A student investigated the rate of reaction between calcium carbonate marble chips and hydrochloric acid. From graph :- The rate of reaction between the small marble chips and dilute hydrochloric acid is higher compared to the rate of reaction between the large marble chips and dilute hydrochloric acid.

    Label this line A. This is because there is a bigger surface area meaning a larger surface for the acid to react with. Click each image to see positive and negative results of the acid test.