# Reaction (rate) between magnesium ribbon and hydrochloric acid

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• Published: May 31, 2004

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Aim

It is to tell how the reaction between magnesium and hydrochloric acid will be effected if we change the concentration of hydrochloric acid.

Introduction

In the experiment the magnesium reacts with the hydrochloric acid to create magnesium chloride and hydrogen. The balanced formula for this is:

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

Magnesium + hydrochloric acid Magnesium Chloride + Hydrogen

Magnesium will react with hydrochloric acid, because it is higher in the reactivity series than hydrogen. The magnesium displaces the hydrogen in the acid, so it forms magnesium chloride and hydrogen gas.

There are many variables that I can change, which are the temperature and concentration of the hydrochloric acid, and the mass and the surface area of the magnesium strip. This is all true because they all link to the collision theory of particles colliding with enough energy to make a reaction. It is based on the idea that for a chemical reaction to take place, the reacting particles have to hit each other hard enough to break or form new bonds. This is called a successful collision. When particles get stimulated or increased in number, the reaction will increase in rate because faster collisions will take place making more successful collisions.

This diagram shows five solutions hydrochloric acid and magnesium ribbon that are reacting. The arrows represent a simplified way to show how many successful collisions occur each second; therefore the more arrows there are, the faster the rate of reaction. They show how different factors can affect the rate of reaction against these two reactants (magnesium and hydrochloric acid). The original diagram shows how the solution will be with 1M hydrochloric acid and 5cm of magnesium strip. This is to compare with the other diagrams to see what the change is and if the reaction rate has decreased or increased.

The first one is to see what will happen if I change the temperature of the solution. As the temperature increases the speed and the power at which the acid particles hit each other increases, making the number of successful collisions with the magnesium strip increase.

The second one is to show how increasing the mass of the magnesium strip can increase the rate of reaction slightly because of the increased surface area but it is only slightly increased on the sides and so this is proportional to the rate of reaction of the original diagram. It is only slower than the original reaction because there is more of it to react with and produces more of the products.

Figure 3 shows the concentration of the hydrochloric acid increased so there are more particles to have more successful collisions. This is a faster reaction then the original reaction.

The final reaction has the same amount of particles of acid and the magnesium, but the magnesium has been cut to increase the surface area. This makes the acid particles more likely to have more successful collisions each second than the original reaction.

There are also many factors that I could record like the weight of the solution and the time it took for the magnesium strip to dissolve, but I am only recording the hydrogen produced. I chose this because I can make all the different concentrations of acid and I will be able to record it accurately. The only variable I am changing for this experiment is the concentration of the hydrochloric acid (measured in M), and maybe some that I have to keep constant all the time.

Prediction

I think that if I increase the concentration of acid I will get a faster rate of reaction therefore the gradient of the line on the graph of results will get steeper with increasing concentration. I have supported this with the explanation of the collision theory (above). As the concentration of acid increases the number of acid particles also increases, this will therefore increase the number of successful collisions with the magnesium. For example, a 2M acid will have twice...