We should know everything about the topic of “Diffusion coefficient and temperature”. In this article we are going to briefly explain about the relationships and several impacts which are related with the diffusion coefficient and temperature.

**Diffusion coefficient is a constant of physical quantity and dependent in temperature and size of the molecules. Diffusion coefficient can be explain as the less time taken for diffusion for a particular material to another material and temperature can explain as the quantity of a physical substance coldness or hotness.**

**Diffusion Coefficient:**

The term diffusion coefficient can be described as, **the parameters proportionality factor which is constant between the molar flux by the diffusion of the molecular and gradient for diffusion or driving force.**

The diffusion coefficient can be determine using this formula,

D = D_{0}e^{EA}/KT

Another term for the diffusion coefficient is **diffusivity**. In S.I the unit of diffusion coefficient is **square meter/second**. The diffusion coefficient is a physical quantity which is remains constant. The physical constant factor is dependent upon some physical properties such as **pressure, temperature, diffusing substance and size of the molecules.**

**Temperature**:

A physical quantity which can be **describe as the degree for a substance which could be stay in hot or cold condition**. In each and every substance temperature is present. This physical quantity is a part of thermal energy which is produce by the help of heat. We always should remember heat and temperature both are different.

The common symbol which is used to identify the temperature is T. The S.I unit of the temperature is Kelvin in others method lots of units are used such as Degree Centigrade, Degree Fahrenheit, Degree Rankine, and Degree Kelvin. By the help of thermometer temperature is measure.

**Diffusion coefficient and temperature relationship:**

From the **Fick’s law** a clear concept we can gain about the diffusion coefficient or diffusivity. Diffusion coefficient is a constant of physical quantity which is dependent upon the temperature.

**The diffusion coefficient and temperature relationship is directly proportional to each other means if the coefficient of diffusion is increases then the temperature is also gradually increases as well as if the value of coefficient of diffusion is decreases then the temperature is also decreases.**

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For different substances the coefficient of diffusion can be estimate from different equations. The diffusion of coefficient can be estimate in three states,

**Solid: **

The value of diffusion coefficient for the solid substance can be estimate from the **equation of Arrhenius**.

Mathematically it can be derive as,

D = D_{0}exp – (E_{a}/RT)

Where,

D = the coefficient of diffusion for solid substance and its unit is square meter per second

D_{0}= Greatest value of the coefficient of diffusion at infinite temperature and its unit is square meter per second

E_{a}= Energy for the activation for coefficient of diffusion it can be expressed in Joule per mol

R = Universal gas constant and its value is 8.314 Joule per mol-Kelvin

T = Absolute temperature and expressed in Kelvin

**Liquid:**

** **The value of diffusion coefficient for the liquid substance can be estimate from the **equation of Stokes – Einstein**.

Mathematically it can be derive as,

D_{T1}/ D_{T2} = T_{1}/T_{2} x μT_{2}/μT_{1}

Where,

D = The coefficient of diffusion for liquid substance and its unit is square meter per second

T_{1} = Initial of the absolute temperature expressed in Kelvin

T_{2} = Final of the absolute temperature expressed in Kelvin

μ=Dynamic viscosity for the solvent of the liquid Pascal second

**Gas:**

** **The value of diffusion coefficient for the gas substance can be estimate from the **theory of Chapman – Enskong**.

Mathematically it can be derive as,

Where,

D = Diffusion coefficient for the gases substance which unit can be expressed as square cm per second

A = Empirical coefficient which value is

T = Absolute temperature which unit is Kelvin

M = Molar mass which is expressed as gram per mol

P = Pressure which is expressed as atm

Ω= Temperature of coefficient of diffusion for solid substance which depend on collision integral

σ_{12}= Average collision diameter for 1/2 ( σ1+ σ2)

A particular coefficient of diffusion for a gas substance range is between 10^{-6} to 10^{-4} square meter per second. By contrast the diffusion of coefficient in the liquid substance is very slow. In aqueous the liquid substance diffusion coefficient range in between 10^{-9} to 10^{-8} square meter per second.

**Diffusion coefficient temperature curve:**

In this section diffusion temperature curve is plotted and from this curve we easily can understand the relationship between the coefficient of diffusion and temperature and how it works.

**Diffusion coefficient graph is given below,**

**Diffusion coefficient table:**

The coefficient of diffusion is physical constant which is depend upon the physical properties among them temperature is most common property.

**The coefficient of diffusion is a physical constant which is commonly experiment and after that it is presented as a table. The coefficient of diffusion table for liquid, gas, and solid substance is presented in table below.**

**Frequent Asked Questions:**

**Question.1. Discuss the factors which are affected Coefficient of diffusion.**

**Solution: The constant physical quantity coefficient of diffusion affected by some physical properties which mainly causes the rate of flow in diffusion coefficient.**

**The factors are discusses briefly in below section,**

**Temperature****Pressure****Size of the molecular of diffusion substance****Surface area****Viscosity of the liquid solvent**

**Temperature:**

A molecule of a substance if moves in a speedy motion then the kinetic energy can be posses. At that moment in the system the physical property temperature is sum up then the molecule of the substance mix up very quickly due to present of the kinetic energy experienced by each other molecule of the substance.

The rate of temperature if an increase then the rate of coefficient of diffusion is also increases and if the rate of temperature if a decease then the rate of coefficient of diffusion is also decreases. Temperature and diffusion coefficient is directly proportional to each other.

**Pressure**:

In general factor pressure is influence the coefficient of diffusion in gases substance. In this case when inside pressure is gradually increases the present molecules come very closer and the rate of diffusion is increases.

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The rate of pressure is increase then the rate of coefficient of diffusion is also increases and if the rate of pressure is decease then the rate of coefficient of diffusion is also decreases. Temperature and diffusion coefficient is directly proportional to each other.

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**Size of the molecular of a diffusion substance:**

Size of the molecular of a diffusion substance is one of the most common and vital factor for the coefficient of diffusion.The heavy molecule movement in the diffusion system is very slow than the lighter molecule. So, the process of the diffusion is dependent upon the molecules.

The rate of size of the molecule of a diffusion system increase then the rate of coefficient of diffusion is decreases and if the rate of size of the molecule of a diffusion system increases then the rate of coefficient of diffusion is decreases. Size of the molecule of a diffusion system and diffusion coefficient is indirectly proportional to each other. ** **

**Surface area: **

In the large amount of surface area the rate of diffusion coefficient motion is increases and the speed will be also become quicker.

**Viscosity of the liquid solvent**:

If the viscosity present in the diffusion system is very thick then the rate of diffusion coefficient became less because in the thicker medium the molecule takes time to solvent.

The rate of viscosity of the liquid solvent of a diffusion system increase then the rate of coefficient of diffusion is decreases and if the rate of viscosity of the liquid solvent of a diffusion system increases then the rate of coefficient of diffusion is decreases. Size of the molecule of a diffusion system and diffusion coefficient is indirectly proportional to each other.

Hi..I am Indrani Banerjee. I completed my bachelor’s degree in mechanical engineering. I am an enthusiastic person and I am a person who is positive about every aspect of life. I like to read Books and listen to music.