Reactivity - Chemistry

Collision Theory

For a reaction between two particles to occur, the particles must collide and a collision must be effective. The more frequently collisions occur the faster the reaction is. A collision is very effective when reactive particles collide with enough kinetic energyand the correct orientation to break existing bonds between bonds between particles.

The start of the reaction is where the concentration of the reactants is relatively high. So the amount of reactant particles in a unit volume is high. Therefore the number of collisions and rate of reaction is high. The end of the reaction is where the concentration of reactants is low as the volume in the container is the same but the amount of reactants has decreased. Therefore the number of collisions has decreased and the rate of reaction has decreased.

When a catalyst is added, the particles must have a minimum energy for a collision to be efective and the cataylst speeds up the reaction rate without being used up. A catalyst does this by providing an alternative pathway with a lower activation energy (minimum energy). This means a greater fraction of the collisions equals or exceeds the required energy so the reaction rate increases.

The rate of reaction can be increased by increasing the frequency at which the collisions occur, increasing the concentration, increasing the surface area or increasing the temperature. Also if the energy of the collisions so that more collisions reach the activation energy. FInally if a catalyst is used.

Equilibrium

An equilibrium reaction is a reaction that proceeds in both directions. The value of Kc is an indication of the extent to which the equilibrium favours products or reactants. If Kc is very large there will be more prodcuts than reactants and if it is very small there is more reactants than products. Kc is found…