Name: how ionic strength changes activity coefficient
Uploaded: 2024-04-04T10:51:15.000Z
Duration: 1 min 17 s
Channel: JoVE

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IPC.8

IPC.8.B

Factors Affecting Activity Coefficient

El coeficiente de actividad de un ion depende de la fuerza iónica de la solución.
Como indica la teoría de Debye-Hückel, cuando la fuerza iónica se acerca a cero, el coeficiente de actividad se aproxima a la unidad.
A medida que la fuerza iónica aumenta de 0 a 0,1 moles por litro, el valor del coeficiente de actividad disminuye.
Sin embargo, con un aumento de la fuerza iónica superior a 0,1 moles por litro, el coeficiente de actividad puede aumentar.
La influencia de la fuerza iónica en el coeficiente de actividad está asociada con la carga del ion, que también influye directamente en el coeficiente de actividad.
Con un aumento de la carga en el ion, la disminución del coeficiente de actividad es aún más pronunciada.
Para una fuerza iónica particular, los iones con las mismas cargas tienen aproximadamente los mismos coeficientes de actividad.
Otro factor importante que afecta el coeficiente de actividad de un ion es el parámetro de tamaño del ion, es decir, el diámetro efectivo del ion hidratado.
Los iones más pequeños con una carga alta tienen diámetros efectivos más grandes y se desvían menos de la idealidad que los iones cargados de manera similar con diámetros más pequeños.

factores que afectan el coeficiente de actividad

La ecuación ampliada de Debye-Hückel indica que el coeficiente de actividad de un ion en una solución acuosa a 25°C depende de tres propiedades parcialmente interdependientes: la fuerza iónica de la solución, la carga del ion y el tamaño del ion.

El valor del coeficiente de actividad de un ion es cercano a uno cuando la solución tiene una fuerza iónica casi nula, es decir, cuando la solución muestra un comportamiento cercano al ideal. A medida que la fuerza iónica de la solución aumenta de 0 a 0,1 mol/L, se observa una disminución en el valor del coeficiente de actividad.

Las soluciones con una fuerza iónica superior a 0,1 mol/L no están bien representadas por la ecuación de Debye-Hückel. En tales soluciones, el coeficiente de actividad de un ion puede exceder la unidad. La fuerza iónica de la solución está estrechamente relacionada con la carga de los iones presentes en la solución, afectando así su coeficiente de actividad. Para una fuerza iónica particular, los iones con menos carga tienen valores de coeficiente de actividad más altos que los iones con una carga más alta. En otras palabras, la desviación de la idealidad es más pronunciada para los iones con carga múltiple que para los iones con carga única.

Los iones con cargas similares suelen tener coeficientes de actividad similares. El factor dominante en las discrepancias de coeficientes es el parámetro del tamaño del ion. El tamaño de los iones describe el diámetro efectivo de un ion hidratado, e incluso los iones con cargas similares tienden a tener diferentes grados de hidratación y, por lo tanto, diferentes tamaños de iones. Los iones con cargas similares pueden hidratarse en diferentes grados, lo que da como resultado diferentes diámetros efectivos. Estos diámetros se conocen como parámetros de tamaño de iones. Los iones con parámetros de tamaño de ion más pequeños se desvían más de la idealidad, lo que resulta en un coeficiente de actividad más bajo que aquellos con parámetros de tamaño de ion más grandes pero con la misma carga.

Factores que afectan el coeficiente de actividad

El coeficiente de actividad de un ion depende de la fuerza iónica de la solución.
Como indica la teoría de Debye-Hückel, cuando el ...

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how ionic strength changes activity coefficient

The activity coefficient of an ion in water depends on ionic strength, ion charge, and ion size. The extended Debye-Hückel equation describes these effects for aqueous solutions at 25°C. These three factors are partly linked, so changes in one can influence the others.

When a solution has almost zero ionic strength, the activity coefficient is close to one. That means the solution behaves almost ideally. As ionic strength rises from 0 to 0.1 mol/L, the activity coefficient usually drops. Solutions with ionic strength above 0.1 mol/L are not well described by the Debye-Hückel equation, and the activity coefficient may even become greater than one.

Ion charge also affects the activity coefficient because ionic strength depends on the ions present in the solution. At the same ionic strength, ions with lower charge usually have higher activity coefficient values than ions with higher charge. This means multiply charged ions show a larger departure from ideal behavior than singly charged ions. Ions with similar charges often have similar activity coefficients.

Ion size is the main reason that activity coefficients can still differ for ions with the same charge. Ion size refers to the effective diameter of a hydrated ion, which depends on how much water surrounds it. Ions with similar charges can be hydrated to different extents, so they can have different ion size parameters. Smaller ion size parameters lead to greater deviation from ideal behavior and a lower activity coefficient than larger ion size parameters for ions with the same charge.

How Ionic Strength Changes Activity Coefficient

how-ionic-strength-changes-activity-coefficient

ionic strength: overview

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Activity Coefficient in Ionic Solutions

Activity coefficient in ionic solutions describes how much a species behaves like its measured concentration. Activity is the effective concentration of a solute in solution. It equals the molar concentration multiplied by the activity coefficient, which is a unitless number. The activity coefficient depends on the total ionic strength of the solution. It shows how far a solution is from ideal behavior. When ionic strength is very low, the activity coefficient of an ionic species is close to...

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Salt effect changes how a sparingly soluble salt dissolves when an inert salt is added. The size of this effect depends on the ionic strength of the solution. Ionic strength reflects how strongly the ions in the solution interact. In solution, the activity of a species is the product of its concentration and its activity coefficient. A redefined equilibrium constant must account for these activity effects when the ionic strength is moderately high. This form is also called the thermodynamic...

factors affecting activity coefficient

The activity coefficient of an ion in water depends on ionic strength, ion charge, and ion size. The extended Debye-Hückel equation describes these effects for aqueous solutions at 25°C. These three factors are partly linked, so changes in one can influence the others. When a solution has almost zero ionic strength, the activity coefficient is close to one. That means the solution behaves almost ideally. As ionic strength rises from 0 to 0.1 mol/L, the activity coefficient usually drops.

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key terms and concepts

Learn how ionic strength, ion charge, and ion size affect activity coefficients in aqueous solutions using the extended Debye-Hückel equation.

How Ionic Strength Changes Activity Coefficient | JoVE K12

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How Ionic Strength Changes Activity Coefficient

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