The effect of concentration on the rate of reaction of Magnesium with Sulphuric Acid.

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The affect of concentration on the rate of reaction of Magnesium with Sulphuric Acid.

Aim

My aim is to determine how the concentration of sulphuric acid affects the rate of reaction between magnesium and sulphuric acid.

I am going to do this experiment five times with five different concentrations: 0.2, 0.4, 0.6, 0.8, and 1mol.  The concentration of the acid is recorded in moles per decimetre cubed (mol/dm³).  I am going to repeat the experiment for each concentration three times to make my results more reliable.

Introduction

A rate is a measure of the change that happens in a single unit of time.  A reaction is when particles called reactants collide and form new substances.  Theses substances which are created are called products.  The rate of a chemical reaction is how fast the reactants react against each other.  Some reactions happen very fast, e.g. an explosion, while other reactions will be much slower, e.g. rusting.

The reactant particles are only able to react when they successfully collide with each other.  Not all collisions are successful because the particles don’t have the correct activation energy.  Activation energy is the minimum energy required before a reaction can occur.  

There are several factors that can increase or decrease the chance of a successful collision.  The factors that affect the rate of the reaction are;

  • Temperature – when we increase the temperature, we give the particles energy, which makes the particles move faster.  Therefore the particles collide more and they are more likely to have the correct activation energy.  The greater the temperature, the faster the rate of a reaction.

  • Surface Area – when we increase the surface area of the reactants we increase the number of particles available for a successful collision.  If we powder the solid metal magnesium, we increase the rate of the reaction because when the metal is powdered, more atoms are exposed, where as in the solid magnesium, the particles can only collide with the atoms on the outside of the metal.

  • Concentration – if we make one reactant more concentrated we increase the number of sulphuric acid particles in a particular volume.  Therefore we increase the chance of a successful collision and the more successful collisions there are, the faster the reaction.

  • Catalyst – a catalyst is a substance that increases the rate of a reaction without being used up.  It provides an alternative route for a chemical reaction.  The alternative route requires a lower activation energy.  Where a catalyst is present in a reaction, a collision needs less energy in order to be successful. Therefore there are more successful collisions, so there is a faster rate.
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We can measure rate in lots of ways, though the most common ways are;

  1. colour change
  2. pH change
  3. volume of a gas
  4. appearance of a precipitate

The rate of the experiment does not stay constant, it is the greatest at the start, and becomes slower throughout the experiment.  This is because throughout the experiment the energy gradually decreases.

We can either measure the amount of reactant used up per unit of time or the amount of product produced per unit of time to find the rate.

For this experiment I am going to find the rate ...

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Good report, some solid scientific theory supported by valid data. The data could be adjusted to cover a more appropriate range. The evaluation should also be extended. Generally a good effort, though more scientific theory and vocabulary could be used to support the prediction. Improvements to the investigation write up have been suggested throughout.