Dr Rana Hamza Shakil thank you for your contribution to the discussion

As the temperature increases, the number of effective collisions increases, thereby decreasing the activation energy of the system. With this, the rate of reaction increases. Two reactions with different activation energies have the same rate at room temperature. For both exothermic as well as endothermic reactions it is not a necessary condition for the activation energy to be equal to the Enthalpy change as activation energy is always greater than the Enthalpy change. As temperature increases, molecules gain energy and move faster and faster. Therefore, the greater the temperature, the higher the probability that molecules will be moving with the necessary activation energy for a reaction to occur upon collision. Activation energy is the minimum energy with which reactants must collide in order for a reaction to occur. The source of the activation energy needed to push reactions forward is typically heat energy from the surroundings. The Heat of Reaction is the change in the enthalpy of a chemical reaction. For an endothermic reaction, the magnitude of Ea is always greater than △H. For an exothermic reaction, the magnitude of Ea is always greater than △H. For an exothermic reaction, adding a catalyst will decrease the magnitude of △H. The temperature sensitivity is measured in terms of Activation Energy, Ea, the higher the activation energy, the more the reaction is accelerated by increasing temperature. The rate of a reaction depends on the temperature at which it is run. As the temperature increases, the molecules move faster and therefore collide more frequently. The molecules also carry more kinetic energy.The activation energy has to do with (almost always) 2 molecules hitting each other at the right orientation and energy, and changing their structure as a result of that. Higher temperature means more molecules are able to do this, which is great, but the energy required for 2 molecules to react doesn't change. Increasing the temperature increases reaction rates because of the disproportionately large increase in the number of high energy collisions. It is only these collisions (possessing at least the activation energy for the reaction) which result in a reaction. The reaction rate with a large Ea increases rapidly with increasing temperature, whereas the reaction rate with a smaller Ea increases much more slowly with increasing temperature. Activation energy is inversely proportional to the rate of reaction. As the activation energy increases, the rate of reaction decreases. The activation energy of a chemical reaction is closely related to its rate. Specifically, the higher the activation energy, the slower the chemical reaction will be. The higher the activation energy, the more energy the particles will need when they collide. if the activation is low, reactions tend to occur faster than higher activation energy. k = Ae - Ea RT where k is the rate constant A is the pre exponential factor Ea is the Activation energy R is the gas constant T is the temperature. With a lower activation energy barrier, a greater percentage of reactant molecules are able to have effective collisions, and the reaction rate increases.The addition of a catalyst to a reaction lowers the activation energy, increasing the rate of the reaction.

Dear Doctor

"Key Points

• Reactions require an input of energy to initiate the reaction; this is called the activation energy (EA).
• Activation energy is the amount of energy required to reach the transition state.
• The source of the activation energy needed to push reactions forward is typically heat energy from the surroundings.
• For cellular reactions to occur fast enough over short time scales, their activation energies are lowered by molecules called catalysts.
• Enzymes are catalysts.

Key Terms

• activation energy: The minimum energy required for a reaction to occur.
• catalysis: The increase in the rate of a chemical reaction by lowering its activation energy.
• transition state: An intermediate state during a chemical reaction that has a higher energy than the reactants or the products.

Key Points

• When the concentrations of the reactants are raised, the reaction proceeds more quickly. This is due to an increase in the number of molecules that have the minimum required energy. For gases, increasing pressure has the same effect as increasing concentration.
• When solids and liquids react, increasing the surface area of the solid will increase the reaction rate. A decrease in particle size causes an increase in the solid’s total surface area.
• Raising the reaction temperature by 10 °C can double or triple the reaction rate. This is due to an increase in the number of particles that have the minimum energy required. The reaction rate decreases with a decrease in temperature.
• Catalysts can lower the activation energy and increase the reaction rate without being consumed in the reaction.
• Differences in the inherent structures of reactants can lead to differences in reaction rates. Molecules joined by stronger bonds will have lower reaction rates than will molecules joined by weaker bonds, due to the increased amount of energy required to break the stronger bonds.

Key Terms

• catalyst: A substance that increases the rate of a chemical reaction without being consumed in the process.
• activation energy: The minimum amount of energy that molecules must have in order for a reaction to occur upon collision."

Dr Sundus F Hantoosh thank you for your contribution to the discussion

No, activation energy is not always greater than heat of reaction. The heat of reaction (∆H) is the difference in energy between the reactants and products of a reaction. It can be either positive (endothermic reaction) or negative (exothermic reaction). The activation energy (Ea) is the minimum amount of energy required for the reactants to collide and react. It is always positive.

In an endothermic reaction, the heat of reaction is positive, meaning that energy is absorbed from the surroundings. The activation energy must be greater than the heat of reaction in order for the reaction to occur. This is because the reactants must absorb enough energy to reach the activation energy barrier before they can react.

In an exothermic reaction, the heat of reaction is negative, meaning that energy is released to the surroundings. The activation energy must still be positive, but it can be less than the heat of reaction. This is because the reactants already have some energy, so they don't need to absorb as much energy to reach the activation energy barrier.

The relationship between temperature and activation energy is exponential. This means that a small increase in temperature can lead to a significant increase in the reaction rate. This is because a higher temperature means that the reactant molecules have more kinetic energy. This makes it more likely that they will collide with enough energy to overcome the activation energy barrier.

In general, a higher activation energy means a slower reaction rate. This is because the reactant molecules need to collide with more energy in order to react. However, there are other factors that can affect the reaction rate, such as the concentration of the reactants and the presence of a catalyst.

Here is a table summarizing the relationship between activation energy, heat of reaction, and reaction rate:

Dr Murtadha Shukur thank you for your contribution to the discussion

I believe that for both exothermic as well as endothermic reactions it is not a necessary condition for the activation energy to be equal to the Enthalpy change as activation energy is always greater than the Enthalpy change. If the temperature is higher, the reactant molecules have a higher kinetic energy, and thus the energy difference between the threshold energy and the energy of the molecules will decrease, that is, the activation energy will decrease. Activation energy is the minimum energy with which reactants must collide in order for a reaction to occur. The source of the activation energy needed to push reactions forward is typically heat energy from the surroundings. The Heat of Reaction is the change in the enthalpy of a chemical reaction. The temperature sensitivity is measured in terms of Activation Energy, Ea, the higher the activation energy, the more the reaction is accelerated by increasing temperature. Activation energy and temperature are inversely proportional to each other. The activation energy is not related to the temperature. It's a result of the need to break some bonds during the process. Breaking bonds takes energy. Higher temperatures means there is more kinetic energy in the system and hence, a higher probability that some of that energy will get to the bond and break it. When the temperature increases, the fraction of molecules that have kinetic energies more than the activation energy of the reaction increases. Therefore, the total activation energy of the reaction decreases. The activation energy of a chemical reaction is closely related to its rate. Specifically, the higher the activation energy, the slower the chemical reaction will be. At a given temperature, the higher the Ea, the slower the reaction. The fraction of orientations that result in a reaction is the steric factor. The frequency factor, steric factor, and activation energy are related to the rate constant in the Arrhenius equation: k=Ae−Ea/RT. The rate determining step is the reaction with the highest activation energy in a reaction mechanism. To go from A+B to C the energy of reaction increases. This increase is the activation energy. With a lower activation energy barrier, a greater percentage of reactant molecules are able to have effective collisions, and the reaction rate increases. The addition of a catalyst to a reaction lowers the activation energy, increasing the rate of the reaction. Once reactants have absorbed enough heat energy from their surroundings to reach the transition state, the reaction will proceed. The activation energy of a particular reaction determines the rate at which it will proceed. The higher the activation energy, the slower the chemical reaction will be. As the temperature increases, the molecules move faster and therefore collide more frequently. The molecules also carry more kinetic energy. Thus, the proportion of collisions that can overcome the activation energy for the reaction increases with temperature.