Investigation on how the rate of reaction changes as the concentration of an acid changes

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Chemistry Coursework 01 May 2007 Alex Hall (J)

Investigation on how the rate of reaction changes as the concentration of an acid changes

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The investigation that we are studying in this piece of Coursework, is how the rate of the reaction between Magnesium and Hydrochloric Acid changes, as the concentration of the Acid is decreased.

The equation for this investigation is as follows:

Mg (s) + 2HCl (aq) MgCl2 (aq) + H2 (g)

I predict that as the concentration of the acid decreases, the rate of reaction will also decrease. Collision Theory says that the more concentrated the reactants, the more collisions will occur. This also explains why the reaction is quickest at the start; it is because the reactants are in their most concentrated state. As the reaction progresses, the concentration of the reactants decreases, and therefore so does the rate of the reaction. In order for the reaction to take place, the particles must collide; and secondly, the smallest amount of energy, the activation energy must be reached. If the activation energy is very high, then there will be a small number of particles able to react, and therefore the reaction rate will be slower. On the other hand, if the activation energy is very low, then more particles will reach that amount of energy sooner and the rate of the reaction will be faster. If the particles collide properly given a bit of help from the activation energy, then the reaction will happen. The reaction is accelerated if the number of collisions is increased.
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The variables in this reaction play a big part in the rate. We conclude from the title of the investigation that there must be a link between the time taken for the Magnesium to dissolve, and the different concentrations of acid. The concentration of any substance is the amount of particles in a given volume. The particles in a high concentration of acid are crowded more, and therefore react quicker. The higher the concentration of the acid, the quicker the reaction and therefore the rate of the reaction increases. The concentration of the acid is known as the ...

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