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Why rate increases with concentration

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Chemistry coursework Background knowledge Some reactions are fast and some are slow. For example; when silver nitrate is mixed with sodium chloride, a very fast reaction occurs, whereas rust forming on a heap of scrap iron is usually a very slow reaction. In order for reactions to take place; the particles must collide with each other, and the collision must have enough energy. The energy is normally given to the particles in heat. If there are lots of successful collisions in a given minute, then a lot of hydrogen is produced in that minute. I.e. the reaction goes quickly - its rate is high. If there are not many then its rate is low. Therefore the rate of reaction depends on how many successful collisions there are in a given unit of time. ...read more.


But they get used up during successful collisions, and as time goes on, there is a constant decrease in this number therefore the reaction slows down. Why rate increases with temperature. When reacting substances are heated, the particles take in energy. They move faster, which means they collide more often and with more energy. So there are more successful collisions and the rate goes up. This is also true with reactions that depend on light energy such as photosynthesis. Why rate increases with surface area. The reaction between a solid and a liquid is major. The acid particles can only collide with the outer most particles of the solid. Whereas, the acid particles can collide with any of the liquid particles as they are all free to move. ...read more.


Subsiquently 80?C reacted too quickly which resulted in an inaccuracy in my timing. It is very hard to time accuratly to 2.7 seconds. To covercome this problem, I changed the concetration of the thiosulfate to 10ml3 of thiosulfate and 40ml3 of distilled water. This means that theoretically there are less thiosulfate molecules for the hydrochloric acid to collide with and therefore react slower. Another commodity that I obtained, whilst performing the preliminary experiment, was the method that I had chosen to heat the chemicals, wasn't very accurate. I have made it so that both the chemicals are heated together in a bigger water bath Resultes table Temperature (?C) Time (sec) #1 Time (sec) #2 Average time (sec) 20 170 133 151.50 30 90 121 105.50 40 72 80 76 50 51 61 56 60 33 42 37.50 70 21 32 26.50 Tim Bishop ...read more.

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