The essence of kinetic-molecular theory is that particles in a substance move randomly as a result of the kinetic energy that they possess. However, because of the random nature of these movements and collisions, not all particles in a substance at any one time have the exact same value of kinetic energy. Thus, it is the average kinetic energy. Kinetic energy is directly proportional to temperature.
6.2.2 Describe the term activation energy, Ea.
The minimum energy required for a chemical reaction to take place.
6.2.3 Describe the collision theory.
Reactions take place as a result of particles colliding and then undergoing a reaction. The particles must have sufficient energy and correct orientation.
6.2.4 Predict and explain, using the collision theory, the qualitative effects of particle size, temperature, concentration and pressure on the rate of a reaction.
- Particle size
The smaller the particles, the faster the reaction. Reaction happens on surface and large area = smaller SA.
- Temperature
Increase temperature, increase rate of reaction. More sufficient energy particles and more collisions
- Concentration
Increase concentration, increase rate of reaction. More collisions at closer proximity
- Pressure
Increase pressure, increase rate of reaction. More collisions at closer proximity.
6.2.5 Sketch and explain qualitatively the Maxwell-Boltzmann energy distribution curve for a fixed amount of gas at different temperatures and its consequences for changes in reaction rate.
The area under the curve must stay constant. The average temperature which is proportional to KE shifts accordingly. The peak also shifts accordingly.
6.2.6 Describe the effect of a catalyst on a chemical reaction
- Catalyst
Presence of catalyst, increase rate of reaction. Catalyst finds an alternative pathway thus lowering the activation energy.
6.2.7 Sketch and explain Maxwell-Boltzmann curves for reactions with or without catalysts.
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