Non-steady state diffusion Formula

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Concentration at x Distance represents the concentration of the diffusing species at a distance of x from the surface. Check FAQs
Cx=C0+(Cs-C0)(1-erf(d2Dt))
Cx - Concentration at x Distance?C0 - Initial Concentration?Cs - Surface concentration?d - Distance?D - Diffusion Coefficient?t - Diffusion Time?

Non-steady state diffusion Example

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With units
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Here is how the Non-steady state diffusion equation looks like with Values.

Here is how the Non-steady state diffusion equation looks like with Units.

Here is how the Non-steady state diffusion equation looks like.

0.7019Edit=0.3Edit+(0.7Edit-0.3Edit)(1-erf(0.01Edit2800Edit1000Edit))
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Non-steady state diffusion Solution

Follow our step by step solution on how to calculate Non-steady state diffusion?

FIRST Step Consider the formula
Cx=C0+(Cs-C0)(1-erf(d2Dt))
Next Step Substitute values of Variables
Cx=0.3mol/L+(0.7-0.3mol/L)(1-erf(0.01m2800m²/s1000s))
Next Step Convert Units
Cx=300mol/m³+(0.7-300mol/m³)(1-erf(0.01m2800m²/s1000s))
Next Step Prepare to Evaluate
Cx=300+(0.7-300)(1-erf(0.0128001000))
Next Step Evaluate
Cx=0.701887933909575
LAST Step Rounding Answer
Cx=0.7019

Non-steady state diffusion Formula Elements

Variables
Functions
Concentration at x Distance
Concentration at x Distance represents the concentration of the diffusing species at a distance of x from the surface.
Symbol: Cx
Measurement: NAUnit: Unitless
Note: Value can be positive or negative.
Initial Concentration
The Initial concentration is the abundance of a constituent divided by the total volume of a mixture before diffusion or reaction.
Symbol: C0
Measurement: Molar ConcentrationUnit: mol/L
Note: Value can be positive or negative.
Surface concentration
Surface concentration represents the concentration of diffusing species at the surface.
Symbol: Cs
Measurement: NAUnit: Unitless
Note: Value can be positive or negative.
Distance
Distance (length) across which the diffusion is taking place.
Symbol: d
Measurement: LengthUnit: m
Note: Value should be greater than 0.
Diffusion Coefficient
Diffusion coefficient is the proportionality factor D in Fick's law .
Symbol: D
Measurement: DiffusivityUnit: m²/s
Note: Value can be positive or negative.
Diffusion Time
Diffusion Time represents the total time in which the diffusion was taking place.
Symbol: t
Measurement: TimeUnit: s
Note: Value can be positive or negative.
sqrt
A square root function is a function that takes a non-negative number as an input and returns the square root of the given input number.
Syntax: sqrt(Number)
erf
The Gauss error function, denoted by erf, is a sigmoid function that occurs in statistics, probability, and partial differential equations.
Syntax: erf(Number)

Other formulas in Composition and Diffusion category

​Go Diffusion Flux
J=D(ΔCd)
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V1=M1ρ2100M1ρ2+(100-M1)𝜌1
​Go Atom percent to mass percent
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​Go Entropy of mixing
ΔSmix=8.314(XAln(XA)+(1-XA)ln(1-XA))

How to Evaluate Non-steady state diffusion?

Non-steady state diffusion evaluator uses Concentration at x Distance = Initial Concentration+(Surface concentration-Initial Concentration)*(1-erf(Distance/(2*sqrt(Diffusion Coefficient*Diffusion Time)))) to evaluate the Concentration at x Distance, Non-steady state diffusion represents the time dependent diffusion of species, a transient diffusion state. Concentration at x Distance is denoted by Cx symbol.

How to evaluate Non-steady state diffusion using this online evaluator? To use this online evaluator for Non-steady state diffusion, enter Initial Concentration (C0), Surface concentration (Cs), Distance (d), Diffusion Coefficient (D) & Diffusion Time (t) and hit the calculate button.

FAQs on Non-steady state diffusion

What is the formula to find Non-steady state diffusion?
The formula of Non-steady state diffusion is expressed as Concentration at x Distance = Initial Concentration+(Surface concentration-Initial Concentration)*(1-erf(Distance/(2*sqrt(Diffusion Coefficient*Diffusion Time)))). Here is an example- 0.701888 = 300+(0.7-300)*(1-erf(0.01/(2*sqrt(800*1000)))).
How to calculate Non-steady state diffusion?
With Initial Concentration (C0), Surface concentration (Cs), Distance (d), Diffusion Coefficient (D) & Diffusion Time (t) we can find Non-steady state diffusion using the formula - Concentration at x Distance = Initial Concentration+(Surface concentration-Initial Concentration)*(1-erf(Distance/(2*sqrt(Diffusion Coefficient*Diffusion Time)))). This formula also uses Square Root (sqrt), Gauss Error (erf) function(s).
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