(a) What factors determine whether a collision between two molecules will lead to a chemical reaction? (b) Does the rate constant for a reaction generally increase or decrease with an increase in reaction temperature? (c) Which factor is most sensitive to changes in temperature-the frequency of collisions, the orientation factor, or the fraction of molecules with energy greater than the activation energy?

For a collision between two molecules to lead to a chemical reaction, the molecules must satisfy certain conditions: 1. They should possess enough energy during the collision. This minimum energy required for the reaction is called activation energy, represented by \(E_a\). The activation energy is needed to break old bonds and form new bonds. 2. The molecules should be properly oriented. During the collision, the molecules must be aligned properly so that the atoms involved in the bond-breaking and bond-forming process can interact effectively. In summary, a collision between two molecules will lead to a chemical reaction if they both have sufficient energy (greater than or equal to the activation energy) and are properly oriented during the collision.

The rate constant generally increases with an increase in reaction temperature. According to the Arrhenius equation, the rate constant (\(k\)) of a reaction is dependent on the temperature (\(T\)): \(k = A \times e^{-\frac{E_a}{RT}}\) where: - \(A\) is the pre-exponential factor - \(E_a\) is the activation energy - \(R\) is the gas constant - \(T\) is the temperature (in Kelvin) As the temperature increases, the exponential term, \(e^{-\frac{E_a}{RT}}\), becomes larger, which in turn increases the value of the rate constant \(k\). This increase in the rate constant leads to a faster reaction rate.

Out of the factors mentioned, the fraction of molecules with energy greater than the activation energy is most sensitive to changes in temperature. 1. Collision frequency is influenced by the concentration of reactants and the temperature. However, it is relatively less sensitive to temperature changes compared to the activation energy factor. 2. The orientation factor may be influenced by temperature, but its effect is less considerable than the effects of the other factors. The fraction of molecules with energy greater than the activation energy is determined by the Boltzmann distribution. As temperature increases, a larger fraction of molecules will have energy greater than or equal to the activation energy, which leads to a higher probability of effective collisions and a faster reaction rate. This sensitivity to temperature changes explains why the activation energy factor is the most significant factor among the three.