Investigation of the factors affecting the rate of reaction between a metal and an acid.

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Investigation of the factors affecting the rate of reaction between a metal and an acid

This experiment is going to be carried out to relate the speed of a chemical reaction to the concentration of acid in which it takes place.

BACKGROUND KNOWLEDGE

All acids contain hydrogen ions (H+)

A strong acid readily loses the hydrogen ions to water.

A weak acid does not readily lose hydrogen ions to water.

The H+ becomes the H3 O+ ion in water; acids are not acidic unless there is water present to detach the H+.

In hydrochloric acid:

H+ Cl-  +  Water    H3 O+ + Cl-

It is the H3 O+  which reacts with the magnesium.

The rate of reaction

There are many factors which can be changed in order to change the rate of reaction between magnesium and acid. The particles have to collide more often. Increasing the concentration of reactants increases the rate of a reaction. Therefore, increasing the concentration of acid will increase the rate of reaction. This is because there are more particles in the same volume so more collisions are possible every second. Also, the energy of the particles affects the number of successful collisions. The faster the rate of reaction, the more energy in the particles, and therefore a greater success rate. If the particles don't have enough energy, they will just bounce off each other and will not successfully collide. I think that the higher the concentration of hydrochloric acid the higher the number of collisions and the higher the rate of reaction when added to a metal. However there are other factors which will affect the rate of reaction, but in this investigation, we must keep them constant, as we are only investigating the effect of varying the concentration of acid. Temperature is one of these factors. The warmer the solution, the more the particles move around and collide and so the quicker the reaction. If I carry out the experiment in different situations (i.e. in the sunlight, near a window, and later in the shade) then the results will differ, as the heat conditions vary.

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SAFETY

Below is a chart of possible dangers and ways of avoiding them when carrying out the investigation:

METHOD

We set up the apparatus, setting the water level in the burette to roughly 50cm3 and put it in the burette holder, with the open end in water (in an ice cream tub). This stopped the water from falling out the bottom. Before I did this, I made sure that the tap at the top end of the burette was closed. This meant that there was no space for air to get into the tube, therefore the water level stayed ...

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