Factors Affecting Rate of Reaction
There are various factors that affect the reaction rate which are listed below:
- Reactant Concentration
- Order of Reaction
- Nature of Reactant
- Pressure
- Temperature
- Solvent
- Electromagnetic Radiation
- Presence of Light
- Presence of Catalyst
- Surface Area
- Activation Energy
Reactants Concentration
From the Collision Theory, we know that the more the reactant more will be the collision and hence more will be the reaction, hence Rate of Reaction is directly proportional to the concentration of Reactants. Also as the concentrations of the reactants decrease, the rate of reaction decreases. Hence, the Rate of Reaction for a given reaction in terms of concentration of Reactant can be given as
aA + bB ⇢ cC + dD
Rate ∝ [A]x [B]y
Rate = k[A]x [B]y
where
- k is the Rate Constant
- x and y may or may not be equal to the coefficient of the reactant.
The above representation of the Rate of Reaction in terms of concentration of Reactant is called Rate Law.
Order of Reaction
In the above reaction, the sum of x and y is called as Order of Reaction. Say for example if (x + y = 0) then the Order of Reaction is Zero and the Rate of Reaction is independent of the concentration of the reactants.
Nature of Reactant
The Rate of Reaction is dependent on the Nature of the Reactant in the manner that the reaction happens fastest if the Reactants are in Gaseous Phase, slower in Liquid Phase, and slowest in the Solid phase.
Pressure
The effect of Pressure is applicable to the reactants in the gaseous phase. The effect is pressure is the same as the effect of concentration in a reaction. High Pressure of gas means higher concentration and hence the rate of reaction increases.
Temperature
The rate of reaction increases with an increase in the temperature. In many cases, the Rate Constant of reaction becomes nearly double for a 10° rise in temperature. However, an accurate explanation of the dependence on temperature was given by Arrhenius. He gave the below expression for the dependence of the rate constant on temperature
k = A -Ea/RT
where,
- k is Rate Constant
- A is the Pre-Exponential Factor or the Frequency Factor
- Ea is Activation Energy
- R is Gas Constant
- T is Temperature
Solvent
Solvent provides the medium for the solute to dissolve. A higher concentration of solute in the solvent will increase the rate of reaction.
Electromagnetic Radiation
Electromagnetic Radiation provides external energy which increases the rate of reaction.
Presence of light
Some reactions do not take place in the dark but can proceed in the presence of light. For Example: H2 + Cl2 ⇢ 2 HCl. This reaction is known as a “photochemical reaction.”
Presence of Catalyst
The main purpose of the catalyst is to increase the rate of reaction without itself involving in the reactions. So the catalyst increases the reaction rate. A catalyst reduces the activation energy barrier and hence provides an alternate path for the reaction to happen.
Surface area
Greater surface area means more collision to take place and hence, greater is the rate of reaction.
Activation Energy
Activation Energy refers to the minimum amount of energy possessed by the reactant to proceed with the reaction. When the molecules of reactant collide they form an intermediate, to form this intermediate minimum amount of energy is required. This minimum energy is called Activation Energy and the intermediate so formed is called Activated Complex. The Rate of Reaction depends on the Activation Energy in the manner that if the Activation Energy is high then the Rate of Reaction will be low and vice versa. Hence, Activation Energy and Rate of Reaction are inversely related to each other.
Learn more about, Factors Affecting Rate of a Chemical Reaction
Rate of Reaction
Rate of Reaction or Reaction Rate in chemistry is defined as the speed or the rate at which a chemical reaction takes place. The rate of a Chemical Reaction is directly proportional to the increase in the concentration of a product per unit of time and to the decrease in the concentration of a reactant per unit of time. This can vary drastically. Chemical reactions proceed at extensively different speeds depending on the nature of the reacting substances, the type of chemical transformation, the temperature, and other factors.
In this article, you will understand the meaning of rate of a chemical reaction, rate of reaction order, the unit of the rate of reaction, and formulas.
Table of Content
- What is the Rate of Reaction
- Rate of Reaction Formula
- Average Rate of Reaction
- Instantaneous Rate of Reaction
- Unit of Rate of Reaction
- Factors Affecting Rate of Reaction