Introduction
In this investigation I am investigating the reaction between hydrochloric acid and calcium carbonate (known as limestone).
The rate of reaction is basically the speed a reaction takes place- meaning how long it occurs for. Chemical reactions only occur when reacting particles collide with each other with sufficient energy to react. The minimum amount of energy that causes them to react is called the activation energy - simply because it activates the reaction. There are many variables that need to be taken under consideration when measuring the rate of reaction. These can include catalysts, surface area, temperature or concentration of the liquid. In this case the dependant variable is the concentration of the liquid. These variables can either decrease or increase the rate of reaction.
Theoretical Background
When a reaction takes place it has to overcome a minimum energy barrier known as the Activation Energy. If the particles collide with less energy than the activation energy then nothing worth noting happens.
"You won't get a reaction unless the particles collide with a certain minimum energy called the activation energy of the reaction." (Taken from www.chemguide.co.uk). Only those collisions, which have energies equal to or greater than the activation energy result in a reaction taking place. The reason why collisions have to overcome the activation is because every chemical reaction results in bond breaking. The activation energy is all about the breaking of the original bonds. So when the collisions between particles are relatively gentle there isn't enough energy available to start the process of breaking bonds and there the particles do not take part in a reaction. If the particles collide with less energy than the activation energy they simply bounce apart. Only those collisions equal to or greater to the activation energy react.
What is the rate of reaction?
The rate of reaction is the speed of the reaction. It is how quickly a reaction takes place.
There are three ways of measuring the rate of reaction. These are
) Precipitation - this is when a product of the reaction is a precipitate which clouds the solution. Observe a marker through the solution and measure how long it takes for it to disappear.
2) Change in mass (usually a gas given off) - any reaction that produces a gas can be carried out on a mass balance and as the gas is released the mass disappearing is easily measured.
3) The volume of gas given off - this involves the use of a gas syringe to measure the volume of gas given off.
In this investigation the reaction that will take place is
Hydrochloric acid + calcium carbonate calcium chloride + carbon dioxide + water.
2HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l)
Steric Effects
Steric effects arise from the fact that each atom within a molecule occupies a certain amount of space. If atoms are brought too close together, there is an associated cost in energy due to overlapping electron clouds, and this may affect the molecule's preferred shape (conformation) and reactivity.
There are several types of steric effects:
Steric hindrance or steric resistance occurs when the size of groups within a molecule prevents chemical reactions that are observed in related smaller molecules. Although steric hindrance is sometimes a problem, it can also be a very useful tool, and is often exploited by chemists to change the reactivity pattern of a molecule by stopping unwanted side-reactions (steric protection).
Steric attraction occurs when molecules have shapes or geometries that are optimized for interaction with one another. In these cases molecules will react with each other most often in specific arrangements.
Collision Theory
The theory that we use to explain how different variables change the rate of reaction is called the collision theory.
For a reaction to take place, the particles of the substances that are reacting have to collide. If they collide, with enough energy then they will react. The minimum amount of kinetic (movement) energy that two particles need if they are going to react when they collide is called the activation energy.
There are four ways that the rate of reaction can be increased. These are:
) Temperature increases the number of collisions
When the temperature is increased the particles all move quicker. If they're moving quicker, they're going to have more collisions.
Temperature: in a cold reaction mixture the particles are moving quite slowly. This means that the particles will collide with each other less often, with less energy, and so there will be fewer successive collisions. However if we heat the reaction mixture the particles create kinetic energy and so will move more quickly. This enforces the particles to move more quickly.
2) Concentration (or pressure) increases the number of collisions
If the solution is made more concentrated it means there are more particles of reactant knocking about between the water molecules which make collisions between the important particles more likely. In a gas, increasing the pressure mans the molecules are more squashed up together so there are going to be more collisions.
Concentration: if there is a reaction where there is a low concentration of reactants the particles will be much more spread out resulting in less successive collisions and so the reaction will be slower. If the concentration of the reactants is increased then the rate of reaction will be increased because the particles will be more packed (crowded) and so there will be more successive collisions. So increasing the concentration will increase the probability (chance) of particles colliding because there would be more particles crowded together in the same volume and so there would be more collisions - increased rate or reaction. This is the dependant variable and so is the variable I'll be changing.
In this investigation I am investigating the reaction between hydrochloric acid and calcium carbonate (known as limestone).
The rate of reaction is basically the speed a reaction takes place- meaning how long it occurs for. Chemical reactions only occur when reacting particles collide with each other with sufficient energy to react. The minimum amount of energy that causes them to react is called the activation energy - simply because it activates the reaction. There are many variables that need to be taken under consideration when measuring the rate of reaction. These can include catalysts, surface area, temperature or concentration of the liquid. In this case the dependant variable is the concentration of the liquid. These variables can either decrease or increase the rate of reaction.
Theoretical Background
When a reaction takes place it has to overcome a minimum energy barrier known as the Activation Energy. If the particles collide with less energy than the activation energy then nothing worth noting happens.
"You won't get a reaction unless the particles collide with a certain minimum energy called the activation energy of the reaction." (Taken from www.chemguide.co.uk). Only those collisions, which have energies equal to or greater than the activation energy result in a reaction taking place. The reason why collisions have to overcome the activation is because every chemical reaction results in bond breaking. The activation energy is all about the breaking of the original bonds. So when the collisions between particles are relatively gentle there isn't enough energy available to start the process of breaking bonds and there the particles do not take part in a reaction. If the particles collide with less energy than the activation energy they simply bounce apart. Only those collisions equal to or greater to the activation energy react.
What is the rate of reaction?
The rate of reaction is the speed of the reaction. It is how quickly a reaction takes place.
There are three ways of measuring the rate of reaction. These are
) Precipitation - this is when a product of the reaction is a precipitate which clouds the solution. Observe a marker through the solution and measure how long it takes for it to disappear.
2) Change in mass (usually a gas given off) - any reaction that produces a gas can be carried out on a mass balance and as the gas is released the mass disappearing is easily measured.
3) The volume of gas given off - this involves the use of a gas syringe to measure the volume of gas given off.
In this investigation the reaction that will take place is
Hydrochloric acid + calcium carbonate calcium chloride + carbon dioxide + water.
2HCl(aq) + CaCO3(s) CaCl2(aq) + CO2(g) + H2O(l)
Steric Effects
Steric effects arise from the fact that each atom within a molecule occupies a certain amount of space. If atoms are brought too close together, there is an associated cost in energy due to overlapping electron clouds, and this may affect the molecule's preferred shape (conformation) and reactivity.
There are several types of steric effects:
Steric hindrance or steric resistance occurs when the size of groups within a molecule prevents chemical reactions that are observed in related smaller molecules. Although steric hindrance is sometimes a problem, it can also be a very useful tool, and is often exploited by chemists to change the reactivity pattern of a molecule by stopping unwanted side-reactions (steric protection).
Steric attraction occurs when molecules have shapes or geometries that are optimized for interaction with one another. In these cases molecules will react with each other most often in specific arrangements.
Collision Theory
The theory that we use to explain how different variables change the rate of reaction is called the collision theory.
For a reaction to take place, the particles of the substances that are reacting have to collide. If they collide, with enough energy then they will react. The minimum amount of kinetic (movement) energy that two particles need if they are going to react when they collide is called the activation energy.
There are four ways that the rate of reaction can be increased. These are:
) Temperature increases the number of collisions
When the temperature is increased the particles all move quicker. If they're moving quicker, they're going to have more collisions.
Temperature: in a cold reaction mixture the particles are moving quite slowly. This means that the particles will collide with each other less often, with less energy, and so there will be fewer successive collisions. However if we heat the reaction mixture the particles create kinetic energy and so will move more quickly. This enforces the particles to move more quickly.
2) Concentration (or pressure) increases the number of collisions
If the solution is made more concentrated it means there are more particles of reactant knocking about between the water molecules which make collisions between the important particles more likely. In a gas, increasing the pressure mans the molecules are more squashed up together so there are going to be more collisions.
Concentration: if there is a reaction where there is a low concentration of reactants the particles will be much more spread out resulting in less successive collisions and so the reaction will be slower. If the concentration of the reactants is increased then the rate of reaction will be increased because the particles will be more packed (crowded) and so there will be more successive collisions. So increasing the concentration will increase the probability (chance) of particles colliding because there would be more particles crowded together in the same volume and so there would be more collisions - increased rate or reaction. This is the dependant variable and so is the variable I'll be changing.
