(1) Skill area P: PLANNING
Problem:
Investigate the effect of concentration on the reaction between Thiosulphate ions (S2O32-) and H+ ions.
Introduction:
When sodium Thiosulphate solution reacts with acid, a precipitate of sulphur forms. The time taken for a certain amount of sulphur to form can be used to indicate the rate of reaction. In this experiment the effect of concentration of sodium thiosulphate on the rate of this reaction is investigated.
Prediction:
I predict that as the concentration of sodium thiosulphate, (Na2S2O3) in MoLdm-3 increases it will take a shorter time for the sulphur precipitate to form. Thus:
* The higher the concentration, the faster the rate of reaction.
This is also vice-versa,
* The lower the concentration the slower the rate of reaction.
Background Information:
Collision theory: If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. Also, When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. All this can be understood better with full understanding of the collision theory itself:
For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area.
Concentration - If the concentration of a solution is increased there are more reactant particles per unit volume. This increases the probability of reactant particles colliding with each other.
Increasing the concentration of reactant A or B will increase the chance of collision between them and increase the speed of precipitation forming (slower ==> faster).
Pressure - If the pressure is increased the particles in the gas are pushed closer. This increases the concentration and thus the rate of reaction.
Surface Area - If a solid is powdered then there is a greater surface area available for a reaction, compared to the same mass of unpowdered solid. Only particles on the surface of the solid will be able to undergo collisions with the particles in a solution or gas.
Problem:
Investigate the effect of concentration on the reaction between Thiosulphate ions (S2O32-) and H+ ions.
Introduction:
When sodium Thiosulphate solution reacts with acid, a precipitate of sulphur forms. The time taken for a certain amount of sulphur to form can be used to indicate the rate of reaction. In this experiment the effect of concentration of sodium thiosulphate on the rate of this reaction is investigated.
Prediction:
I predict that as the concentration of sodium thiosulphate, (Na2S2O3) in MoLdm-3 increases it will take a shorter time for the sulphur precipitate to form. Thus:
* The higher the concentration, the faster the rate of reaction.
This is also vice-versa,
* The lower the concentration the slower the rate of reaction.
Background Information:
Collision theory: If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. Also, When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. All this can be understood better with full understanding of the collision theory itself:
For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area.
Concentration - If the concentration of a solution is increased there are more reactant particles per unit volume. This increases the probability of reactant particles colliding with each other.
Increasing the concentration of reactant A or B will increase the chance of collision between them and increase the speed of precipitation forming (slower ==> faster).
Pressure - If the pressure is increased the particles in the gas are pushed closer. This increases the concentration and thus the rate of reaction.
Surface Area - If a solid is powdered then there is a greater surface area available for a reaction, compared to the same mass of unpowdered solid. Only particles on the surface of the solid will be able to undergo collisions with the particles in a solution or gas.
