Question

1. DISCUSS ACTIVATED COMPLEX THEORY OF REACTION RATES

2. DISCUSS THE COLLISION THEORY OF REACTION RATES. COMARE THIS WITH THE ACTIVATED COMPLEX THEORY

THANKS

Answer 1

1. Activated complex theory (which is also known as transition state theory ) is a theory used to describe rate of chemical reactions. In this theory we assume a chemical equilibrium with reactants and activated complex (transition state complex). This theory is proposed by Eyring and Polyani. The theory is more accurate when compared to Arrehenius equation which was previously used to determine the rate of reaction. Activated complex theory mainly describes some factors which define the occurance of a chemical reactions which are:

concentration of activated transition complex

rate at which activated complex decomposed to form the product

the path of decomposition of activated complex(either it can decompose to form reactants or it can leads to products).

2. Collision theory is proposed by Trautz . According to this theory, in a chemical reactions only effective collisions between molecules will bring about the reaction. At higher temperature the number of collisions will be higher since the molecules move so fast, thus reaction rate will also be high. The two parameters which are important in the reaction are collision frequency and collision cross section area. Where collision frequency is the rate at which molecules collide and collision cross section is the collision region represented by one molecule to the another. the fraction of collision is directly depend upon temperature and inversely depend upon activation energy.

After comparing all theories Activated complex theory is more reliable than either the Arrhenius equation and Collision Theory. However, it has its limitations, especially when considering the concepts of quantum mechanics. Quantum mechanics discuss a process called tunneling in which particles can cross the energy barrier created by the transition state. This can especially occur with low activation energies, because the probability of tunneling increases when the barrier height is lowered.