Difference Between Rate of Reaction and Rate Constant

Main Difference

The main difference between the rate of reaction and rate constant is that the rate of reaction refers to the mole per sec as the change in molar concentration of reactants and products with time, whereas the rate constant refers to the constant of proportionality of a particular chemical reaction.

Rate of Reaction vs. Rate Constant

Reaction rate defined as the change in the number of reactants and products with time, whereas the rate constant defined as the specific constant of proportionality of a particular chemical reaction. The rate of reaction directly rests on reactants and products’ molar concentrations, while the rate constant does not rest on reactants and products’ molar concentrations. The rate of a reaction indirectly rests on the physical properties like temperature; on the other hand, the rate constant directly rests on the physical properties like temperature.

The rate of reaction mainly needs the time of the completion of a reaction on the flip side; the rate constant does not need the time of the completion of a reaction. The rate of a reaction depends upon pressure, while the rate constant does not depend upon pressure. The rate of reaction can change with the help of catalysts, whereas the rate constant does not show any change in the presence of catalysts.

The rate of reaction always expressed in mole per sec, while the rate constant is taken from the reaction directly. The unit of rate of reaction does not subject to an order of reaction, whereas the unit of a constant rate subject to the order of the reaction or can find out with the help of an order of a reaction. The rate of reaction directly or indirectly depends on the frequency of collisions, whereas the rate constant does not mainly depend on the frequency of collision.

Comparison Chart

Rate of ReactionRate Constant
The reaction rate is defined as the variation in the number of reactants and products with time.Rate constant defined as the specific constant of proportionality of a particular chemical reaction.
Molar Concentration
Rest on the molar concentrationDoes not rest on the molar concentration
Time
Depends on the time of reactionDoes not depend on the time of reaction
Temperature
Indirectly depends on the temperatureEssentially depends on the temperature
Pressure
Depends on pressureDoes not depend on pressure
Catalysts
Depends on catalystsDoes not depend on catalysts
Collision Frequency
Depends on collision frequencyDoes not depend on collision frequency
Order of Reaction
Its unit depends on the order of reactionIts unit does not depend on the order of reaction

What is the Rate of Reaction?

The rate of reaction refers to the mole per sec change in the concentration of reactants and products with time. It also depends on the physical properties like temperature. It fluctuates with the deviation of temperature. It also depends on the time of completion of the reaction. Longer the time, larger will be the value of the rate of reaction.

It depends on temperature indirectly. It can be changed with the change in pressure and catalysts. The main factor that is involved in increasing the value of the rate of reaction is the increase in the frequency of collision of reacting molecules. The units of the rate of reaction can be found with the help of the order of the reaction.

The rate of the reaction always said to increase if the molar concentration of the reactants is decreasing, and the molar concentration of the products is increasing. In the same way, the rate of reaction always said to decrease if the molar concentration of reactants is increasing, and the molar concentration of products is decreasing.

What is Rate Constant?

Rate constant defined as the specific constant of proportionality. It does not rest on the concentration of moles. It is importantly rested on the physical properties like temperature. It can only change with the change in temperature. Other quantities do not affect the rate constant such as pressure and catalysts.

It also does not depend on the time for completion of a reaction. It does not change whether a reaction occurs in no time or occurs abruptly. The frequency of collision of reacting molecules does not affect changing the rate constant. K can denote it.

This constant is helpful and determining the rate of reaction at any time during the reaction. The increase or decrease in a rate constant can only be determined by the physical properties such as temperature.

Key Differences

  1. The rate of reaction is the change in the number of reactants and products as the time increases, whereas the rate constant is the constant of proportionality present in a certain chemical reaction.
  2. The rate of reaction mainly lies in the molar concentrations of reactants and products, while the rate constant does not lie on the molar concentrations of reactants and products.
  3. The rate of reaction does not directly depend on the physical properties like temperature; on the flip side, the rate constant directly depends on the physical properties like temperature.
  4. The rate of reaction mainly takes the time for the achievement of a reaction; on the flip side, the rate constant does not take the time for the achievement of a reaction.
  5. The rate of a reaction is exposed to pressure while the rate constant does not depend on pressure.
  6. The rate of reaction can change its mechanism with the aid of catalysts, whereas the rate constant does not show any change in its mechanism in the occurrence of catalysts.
  7. The rate of reaction is stated in mol per sec, while the rate constant is carried from the reaction right.
  8. The rate of reaction wholly hinges on the frequency of collisions, whereas the rate constant does not lie on the frequency of collision.

Conclusion

The above discussion concludes that the rate of reaction is the molar change in the reactant and product concentration per unit time, whereas the rate constant is proportionality constant of a specific reaction.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss

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