What is the effect of concentration on the rate of a chemical reaction?

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Aim: What is the effect of concentration on the rate of a chemical reaction?

To investigate the reaction between Magnesium (Mg) and Hydrochloric acid (Hcl) and see if by altering the concentration of Hydrochloric acid (Hcl) affects the speed of the reaction.

Scientific Knowledge:  

Mg                 +              2Hcl                                           MgCl2          +        H2

Magnesium          Hydrochloric acid                             Magnesium     Hydrogen

                                                                                          Chloride             gas

                 

                 Reactants                                                                        Products                                                                          

         

All substances are made up of particles. In liquids there is a distance between two particles, because in liquids the particles are not so closely packed together. In gases the particles are really far apart, and there is a substantial gap between the particles. However, in solids particles are closely packed together and there is no space or gap between two particles of solids.

                               If, either in gases or liquids we give these particles a little energy then they start to move. In liquids the movement is not too great because the particles are not very far part, but in gases because the particles are really far apart and this means that particles start to run around. In solids though, particles are really closely packed together, so if they are given a little energy, the start to vibrate as they can’t move around because of not having any space between them. This theory of particles moving in liquids and gases and vibrating in solids is called KINETIC THEORY.

If the particles are moving around in liquids and gases than there is a good chance that these particles will collide with each other. In liquids there is a greater chance of particles colliding with each other, in comparison to the particles in gases as the particles in liquids are more closely packed and although there is space to move, the space is not as great as in gases. In solids there is no chance of particle colliding, as when these particles are given energy they can only vibrate.

                           The collision of moving particles with other particles when they are moving around is called   COLLISION THEORY. When the particles collide with particles of different elements, either they join with each other, or just move apart. This joining of particles depends on the amount of energy given to the particles. If there is enough energy, the particles will join, react and form a new substance.

                           To join two particles together you need energy. The smallest amount of energy required to join two particles and start a reaction is called the ACTIVATION ENERGY. The activation energy differs from particle to particle. Some particles need a lot of energy to join; others do not require a hugely substantial amount of energy to start a reaction. In the end, to have a reaction we need MOVING particle, to bump into each other and we need enough ACTIVATION ENERGY for the particles to join together.

Figure 1              

 

                                                                                     

Figure 2

                                                                                         

In figure 1 there is a low concentration of Hydrochloric acid (Hcl) as the dark black doth representing the Hydrochloric acid (Hcl) are quite few. In figure 2 there is a higher concentration of Hydrochloric acid (Hcl) as the black dots representing Hydrochloric acid (Hcl) are present in substantial numbers. The concentration of Magnesium (Mg) is almost the same in the two Figures.

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In figure two when the particles will be given Activation Energy there is a much higher chance than figure two of collisions as the concentration of Hcl is much higher than in figure 2. This would mean more particles moving around in the same space and that means more chances of a collision, in which two particles will join and form a new substance. In figure one the opposite of figure two will happen. Because there are less particles of Hcl there is less chance of a collision, as there will be less particles of Hcl moving around in ...

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