The Effect of Concentration on the Rate of Reaction

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The Effect of Concentration on the Rate of Reaction Planning AIM To look at the change in concentration on the rate of reaction BACKGROUND THEORY The rate of reaction tells us how quickly a chemical reaction happens. We can work it out after doing an experiment. We can measure how much reactant is used up in a certain time or how quickly products are formed. We then work out what 1/time taken is and that gives us the rate. The rate of the reaction can be affected by a number of things: Concentration Surface area Temperature Catalysts The collision theory The greater the surface area, the faster the rate of reaction. This is because more atoms are exposed and ready to react. The higher the temperature, the faster the rate of reaction. This is because raising the temperature makes the particles collide more often in a certain time and it makes it more likely that collisions will result in a reaction. Catalysts speed up chemical reactions therefore increase the rate of reaction. The collision theory is that the more collisions between particles in a given time, the faster the reaction. This goes for all of the above factors and is the basis for why reactions take place. PRELIMINARY WORK For our preliminary work, we decided the factor we were going to investigate was how concentration affects the rate of reaction. We used sodium thiosulphate (Na2 S2 O3) as our concentrated solution, hydrochloric acid and water to carry out our experiment. We did the experiment with two concentrations of sodium thiosulphate, 40gpl and 25gpl, to see which we would use for our main investigation. On a two pieces of paper, we drew a cross and place a beaker on top of the crosses. Into the beakers we poured 25cm3 sodium thiosulphate, the 40gpl solution in one and the 25gpl solution in the other. To each of the solutions we added 5cm3 of hydrochloric acid and started timing.

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