# Rate of reaction and coefficient of the reactan

• Entanglement
In summary: In this case, since the concentration of NO has doubled, there are now twice as many NO molecules as there were before, and consequently the rate of the reaction has quadrupled.
Entanglement
Suppose in the reaction 2 NO + O2 --------> 2NO2

Why when the the concentration of NO is doubled, the rate increases 4 times, I know that the rate is directly proportional to the square of NO concentration (I don't know why) and it's order of reaction is 2 ( I don't why ). but I still can't understand a reason for all of that it seems foggy to me why the coefficient affects the proportionality. It should be intuitive to a chemistry student, I think a simple analogy would be helpful, thanks

ElmorshedyDr said:
Why when the the concentration of NO is doubled, the rate increases 4 times, I know that the rate is directly proportional to the square of NO concentration (I don't know why) and it's order of reaction is 2 ( I don't why )

While everything you wrote is correct, it is the wrong way around.

First, we should check what is the reaction order - and the only sure way of doing it is an experiment. Once we know order is 2 everything else follows as a series of conclusions.

Borek said:
While everything you wrote is correct, it is the wrong way around.
First, we should check what is the reaction order - and the only sure way of doing it is an experiment. Once we know order is 2 everything else follows as a series of conclusions.
But in elementary reactions, the order is equal to the coefficient, isn't that true and why ?

ElmorshedyDr said:
But in elementary reactions, the order is equal to the coefficient, isn't that true and why ?

Yes it is true - because we defined it this way. Order of the reaction equals sum of the coefficients from the elementary reaction equation.

Borek said:
Yes it is true - because we defined it this way. Order of the reaction equals sum of the coefficients from the elementary reaction equation.
You really misunderstand me, I know because it's defined like that, I mean why does the number of moles in a balanced question affects the proportionality in the rate equation for an example 2NO + O2 ------> 2NO2 , I2 + H2 -----> 2HI

Supposing that they are elementary reactions
Why in the first equation on doubling the conc of NO the rate increases 4 times but on doubling I2 it increases only 2 times

I already know the conception of the order of reaction and this stuff

but I want an analogy that really clarifies it, or a detailed easy explanation that make it clear and intuitive to a high school student.

Last edited:
If you are looking for intuition - reactions occur when the molecules collide, the more molecules, the more frequent the collisions. Number of collisions for a given kind of a molecule is proportional to its number (or concentration).

## 1. What is the rate of reaction?

The rate of reaction refers to how quickly a chemical reaction takes place, or how fast reactants are converted into products.

## 2. How is the rate of reaction measured?

The rate of reaction can be measured by monitoring the change in concentration of reactants or products over time, or by measuring the amount of product formed in a certain amount of time.

## 3. What factors can affect the rate of reaction?

Factors that can affect the rate of reaction include temperature, concentration of reactants, surface area, presence of a catalyst, and the nature of the reactants and products.

## 4. What is the coefficient of the reactants?

The coefficient of the reactants in a chemical equation represents the number of moles or molecules of each reactant involved in the reaction. It is used to balance chemical equations and determine the stoichiometry of the reaction.

## 5. How does the coefficient of the reactants affect the rate of reaction?

The coefficient of the reactants does not directly affect the rate of reaction. However, it does determine the relative amounts of reactants involved in the reaction, which can indirectly impact the rate of reaction by affecting factors such as concentration and surface area.

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