How Concentration Affects The Speed Of A Chemical Reaction

How Concentration Affects The Speed Of A Chemical Reaction

Aim

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To investigate the effect of concentration of acid, in the reaction

between dilute hydrochloric acid and magnesium ribbon.

Preliminary Research

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The rate of a chemical reaction is the measure of how fast the

reaction takes place. In a reaction particles must collide and

overcome the fixed amount of energy for the reaction to take place.

This energy is called the activation energy. The rate of reaction

depends on four factors:

« Temperature - An increase in temperature produces an increase in

rate of reaction. This is because the kinetic energy of particles

increases causing them to move faster and result in more collisions.

As particles are moving faster, larger proportion of the collisions

will exceed the activation energy and so the rate of reaction

increases.

« Surface Area - If the reactant has a large surface area, there is a

greater surface area for collisions to take place resulting in a

higher frequency of successful collisions and so causing an increase

in the rate of reaction.

« Catalyst - A catalyst is a substance, which can alter the rate of a

reaction but remains chemically unchanged at the end of the reaction.

Catalysts usually speed up a reaction by providing an alternative

pathway for the reaction. It reduces the activation energy and so more

particles will have enough energy to result in a reaction, therefore

increasing the rate of reaction.

« Concentration - This factor is our independent variable and the

effects of this factor will be discussed in the hypothesis.

Hypothesis

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I predict that as the concentration of hydrochloric acid increases the

rate of reaction with the magnesium ribbon will also increase. The

following reaction takes place:

2HCl(aq) + Mg(s) à MgCl2(aq) + H2(g)

An increase in rate of reaction results in more products being formed

and a given volume of hydrogen gas will evolve in a shorter period of