Chemical Factors Affecting Rate of Reaction
We study the rate of chemical reaction in a separate branch of chemistry known as Reaction kinetics. The rate of different chemical reactions may vary.
For example, some reactions occur at an exponentially fast rate, like fireworks detonation. On the other hand, some chemical reactions proceed at a much sluggish rate, like rusting a bare iron sheet.
Sometimes, we have to control this rate of chemical reactions according to our needs and desires - especially while manufacturing a cosmetic or pharmaceutical product in the laboratory.
For this purpose, we alter the rate by changing the chemical factors. By changing these chemical factors, we can structure a reaction as per our desire. These four chemical factors affecting rate of reaction which are given as follows
Related: Learn about the general chemical equation of endothermic and exhothermic reactions.
The rate of a chemical reaction is directly proportional to the concentration of the reactant. In other words, If we increase the concentration of reacting substances in the system, the collision between the reactant molecules will increase per unit of time. Resultantly, the rate of reaction will increase.
The rate of a chemical reaction is directly proportional to its temperature. Since temperature boosts the kinetic energy of reactant molecules, they collide with each other more frequently. Resultantly, more reactants would convert to products.
Surface area and physical states
The physical state of reactants is also the main chemical factor upon which the reaction rate depends. The larger the surface area, the higher the rate of reaction will be. Similarly, if the reactant mixture is homogeneous - all the reactants in one physical form - the rate will be higher than that of heterogeneous reactants.
Catalyst Rate of Reaction
The substance which accelerates a chemical reaction without affecting the nature of the final product is known as a catalyst. These catalysts work by changing the reaction pathway. Thus, the more the concentration of the catalyst, the higher the catalyst rate of reaction will be.
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Determining Chemical Factor or Conversion Factor in a Reaction
Before determining the chemical factor, let us clear the concept that what is the conversion factor, according to analytical chemistry.
What is the conversion factor?
As we know, a balanced chemical equation shows the relative concentrations of reactants and products. Each formula that you see in the equation exhibits the exact mass of substances present in it.
Thus, we can say that the entire equation implies the relationship between the masses of different substances.
For example, in a combustion reaction, CO2 and O2 react with each other such as
It is clear from the equation that there is one mole of CO2, one mole of O2, and two mol of 2CO.
If we calculate the atomic masses of all these reacting species, it would be as follow
CO2 = 2×28 = 56g
O2 = 2×16 = 32g
2CO = 2×44 = 88g
These relative masses are showing the reaction stoichiometry. Since masses of each component vary from the other in a specific proportion, the amount related to the mass of one component from the mass of the other one is called the chemical factor or conversion factor.
Let's clear our concept further by calculating the conversion factor/chemical factor for 2CO and CO2 in a stepwise process
Step 1: Calculate the mass of each component
In the first step we will calculate the mass of each component we have. As we know
This step is very crucial as it also help us while calculating the oxidation state of an element in an compound.
Step 2: Calculate the mass ratio of any two components
In this step we will calculate the mass ratio of any two components.
Mass ratio of
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Thus, the chemical factor which is involved in the conversion of CO2 into CO is 1.57. We can also say that the mass ratio of 2CO: CO2 is 1.57 in the equation mentioned above.
By using the same formula, we can calculate the conversion or chemical factor for any chemical equation. Keep in mind that
"The conversion factors are used to change the unit of one quantity into another one."
For example, in the equation, as mentioned earlier, the components were shown in moles. While calculating the conversion factor, since we used molar masses of compounds, we can say that we used molar masses as a conversion factor.
Related: What are Gas laws and how important are these laws?
Use of Conversion Factors
As stated before, we use the conversion factors chemistry to change the unit of one quantity into another. How? Let's elaborate further on this step-by-step process.
Suppose you have been asked to find the mass of
3.987mol of Al
Step 1: Calculate the molar mass for one mole
As we know,
Step 2: Formulate the conversion factor
We formulate the conversion factor such as
Step 3: Use the conversion factor in the equation
Now, to convert the 3.987mol of Al into mass, we use the conversion factor such as
Thus, in this way, By using unit conversions chemistry, we can convert the unit of aluminum into another unit. If we want to calculate the number of moles from mass, we invert the conversion factor such as
Similarly, we can also use the other chemical units and even the chemical factors like concentration, temperature, and pressure as unit conversions to calculate the stoichiometry of a reaction or to balance redox reaction.