Which of the following has no effect on the rate ofa reaction?
a)degree of branching or size of reactant molecules
b)value of Heat of reaction
c)presence of a catalyst
d)temperature of the reactants
e) concentrations of the reactants
https://www.chem.tamu.edu/class/majors/tutorialnotefiles/factors.htm
Those four, and only those four, affect the reaction rate.
To determine which of the following options has no effect on the rate of a reaction, let's examine each option and its impact on the reaction rate:
a) The degree of branching or size of reactant molecules can actually affect the rate of a reaction. Generally, smaller and more branched molecules tend to react faster compared to larger and less-branched molecules. Therefore, this option does not have no effect on the rate of a reaction.
b) The value of the heat of reaction, also known as the enthalpy change, determines the amount of energy absorbed or released during a chemical reaction. While it may not directly affect the rate, it does impact the reaction's equilibrium position. However, since the question is specifically asking about the rate of the reaction, this option can be eliminated.
c) The presence of a catalyst is known to increase the rate of a reaction. Catalysts provide an alternative reaction pathway with lower activation energy, which accelerates the rate but does not get consumed in the reaction. Therefore, this option does not have no effect on the rate of a reaction.
d) The temperature of the reactants directly influences the rate of a reaction. As the temperature increases, the kinetic energy of the reactant molecules increases, leading to more frequent and energetic collisions that result in a faster reaction rate. Hence, temperature has a significant effect on the reaction rate.
e) The concentrations of the reactants determine the frequency of collisions between reactant molecules. Higher concentrations mean more reactant particles in a given volume, resulting in more collisions and a faster reaction rate. Lower concentrations lead to fewer collisions and slower reaction rates. Therefore, concentration does affect the rate of a reaction.
After analyzing each option, the correct answer is b) the value of Heat of reaction.