Variation of conductivity with dilution- Part 2 | Electrochemistry | Chemistry | Khan Academy

Khan Academy India - English
15 May 202308:18
EducationalLearning
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TLDRThis educational video explores the relationship between molar conductivity (Λm) and concentration, focusing on the graphical representation of this variation. It explains how Λm changes with dilution for both strong and weak electrolytes, highlighting that strong electrolytes show a gradual increase in Λm with dilution, while weak electrolytes exhibit a more significant rise due to increased dissociation. The video demonstrates plotting Λm against the square root of concentration, revealing a linear trend for strong electrolytes and a hyperbolic curve for weak ones. It also introduces the concept of molar conductivity at infinite dilution, Λm∞, which is the y-intercept of the line for strong electrolytes, indicating the maximum conductivity achievable.

Takeaways
  • 📊 The video discusses plotting the variation of molar conductivity (Λm) with concentration graphically to understand the relationship visually.
  • 🔍 Molar conductivity (Λm) is the conductivity of one mole of an electrolyte and varies with the concentration and type of electrolyte.
  • 🧪 Electrolytes can be either strong or weak, with strong electrolytes dissociating completely and weak electrolytes not fully dissociating.
  • 📉 For strong electrolytes, increasing dilution or decreasing concentration leads to an increase in molar conductivity.
  • 📈 For weak electrolytes, dilution results in a higher increase in molar conductivity due to increased dissociation and ion concentration.
  • 🧬 The degree of dissociation (α) for weak electrolytes increases with dilution, leading to more ions and higher molar conductivity.
  • 📚 The equilibrium constant (K) and reaction quotient (Q) are used to understand the shift in dissociation equilibrium with dilution.
  • 📉 The script explains that plotting Λm against the square root of concentration (√C) helps in fitting data points into a straight line for strong electrolytes.
  • 📈 The trend for strong electrolytes is a straight line where molar conductivity increases as concentration decreases, indicating increased dilution.
  • 📊 For weak electrolytes, the trend is a hyperbolic curve showing an even greater increase in molar conductivity with dilution.
  • 🔑 The video also explains the concept of molar conductivity at infinite dilution (Λm∞), which is the y-intercept of the straight line for strong electrolytes.
  • ✍️ The equation of the straight line for strong electrolytes is given as Λm = -B√C + Λm∞, where B is the slope and Λm∞ is the molar conductivity at infinite dilution.
Q & A

  • What is molar conductivity represented by?

    -Molar conductivity is represented by the symbol Lambda, M, and it is the conductivity of one mole of an electrolyte.

  • How does molar conductivity vary with concentration?

    -Molar conductivity varies with concentration depending on the type of electrolyte. For strong electrolytes, molar conductivity increases with dilution or decreased concentration, while for weak electrolytes, the increase in molar conductivity with dilution is much higher due to increased dissociation.

  • What is the difference between a strong electrolyte and a weak electrolyte in terms of dissociation?

    -A strong electrolyte dissociates completely in solution, meaning the dissociation is 100%. A weak electrolyte, on the other hand, does not dissociate completely, and the degree of dissociation increases with dilution.

  • How does the degree of dissociation of a weak electrolyte change during dilution?

    -During dilution, the degree of dissociation (Alpha) of a weak electrolyte increases, leading to more ions in the solution and thus an increase in molar conductivity.

  • What is the equilibrium constant for a weak acid dissociation reaction?

    -The equilibrium constant for a weak acid dissociation reaction is given by the concentration of H+ times the concentration of A- divided by the concentration of HA.

  • How does the reaction quotient (Q) relate to the equilibrium constant (K) when the concentration is reduced?

    -When the concentration is reduced, the reaction quotient (Q) becomes less than the equilibrium constant (K), causing the reaction to shift to the right and increase the dissociation of the weak electrolyte.

  • Why is the square root of molar concentration (sqrt(C)) used on the x-axis when plotting molar conductivity?

    -The square root of molar concentration is used because experimental data fits more easily into a straight line when plotted against it, which simplifies the analysis of the trend.

  • What does the trend of molar conductivity for a strong electrolyte look like when plotted against the square root of concentration?

    -For a strong electrolyte, the trend of molar conductivity when plotted against the square root of concentration appears as a straight line with a negative slope.

  • How does the molar conductivity at infinite dilution (Lambda M Infinity) relate to the graph of a strong electrolyte?

    -Lambda M Infinity is the y-intercept of the straight line on the graph, representing the molar conductivity when the concentration approaches zero.

  • What is the equation of the straight line for the molar conductivity of a strong electrolyte?

    -The equation of the straight line is Lambda M = Lambda M Infinity - B * sqrt(C), where Lambda M is the molar conductivity, Lambda M Infinity is the molar conductivity at infinite dilution, B is the negative slope, and C is the concentration.

  • What additional insight can be gained from the graph of molar conductivity for weak electrolytes?

    -For weak electrolytes, the graph shows a hyperbolic curve, indicating a more significant increase in molar conductivity with dilution compared to strong electrolytes, reflecting the increased dissociation and ion concentration in the solution.

Outlines
00:00
📈 Understanding Molar Conductivity and Its Variation with Concentration

This paragraph introduces the concept of molar conductivity (Λm) and its dependence on the concentration of an electrolyte. It explains that the variation of molar conductivity with concentration is influenced by the type of electrolyte, whether it is strong or weak. For strong electrolytes, complete dissociation occurs, and increasing dilution leads to an increase in molar conductivity. In contrast, weak electrolytes show a higher increase in molar conductivity upon dilution due to increased dissociation. The paragraph also discusses the mathematical representation of this relationship, including the equilibrium constant and reaction quotient, and how these relate to the degree of dissociation (α) during dilution.

05:02
📊 Graphical Representation of Molar Conductivity for Strong and Weak Electrolytes

This paragraph delves into the graphical representation of molar conductivity variation with concentration for both strong and weak electrolytes. It describes the process of plotting molar conductivity against the square root of molar concentration, which helps in fitting the data points into a straight line for strong electrolytes and a hyperbolic curve for weak electrolytes. The paragraph highlights how the molar conductivity increases with increasing dilution for both types of electrolytes but at a more pronounced rate for weak electrolytes. It also introduces the concept of molar conductivity at infinite dilution (Λm∞), which is the y-intercept of the plotted line for strong electrolytes, indicating the conductivity when the concentration approaches zero. The paragraph concludes with the equation representing the straight line for strong electrolytes, emphasizing its significance in understanding the behavior of molar conductivity with concentration changes.

Mindmap
Keywords
💡Molar Conductivity
Molar conductivity, represented by Lambda, M, is a measure of the ability of a solution to conduct electricity, specifically the conductivity of one mole of an electrolyte. It is a central concept in the video, as it explains how this property changes with concentration and dilution. The script discusses how molar conductivity increases with dilution for both strong and weak electrolytes, but the increase is more pronounced for weak electrolytes due to increased dissociation.
💡Concentration
Concentration in the context of the video refers to the amount of solute present in a given volume of solution. It is directly related to molar conductivity, as decreasing concentration (or increasing dilution) affects the degree of dissociation and thus the molar conductivity. The script uses concentration to explain the variation in molar conductivity for different types of electrolytes.
💡Dilution
Dilution is the process of reducing the concentration of a solute in a solution, typically by adding more solvent. In the video, dilution is shown to have a significant impact on molar conductivity, particularly for weak electrolytes, where increased dilution leads to a higher degree of dissociation and, consequently, a greater increase in molar conductivity.
💡Electrolyte
An electrolyte is a substance that dissociates into ions when dissolved in a solvent, thus becoming able to conduct electricity. The video distinguishes between strong and weak electrolytes based on their degree of dissociation. The type of electrolyte determines how molar conductivity varies with concentration and dilution.
💡Strong Electrolyte
A strong electrolyte is one that completely dissociates into ions in solution. The script explains that for strong electrolytes, molar conductivity increases with dilution, but the increase is gradual compared to weak electrolytes, as they are already fully dissociated.
💡Weak Electrolyte
A weak electrolyte is one that only partially dissociates into ions in solution. The video highlights that weak electrolytes show a more significant increase in molar conductivity upon dilution due to an increase in the degree of dissociation, leading to more ions available to conduct electricity.
💡Dissociation
Dissociation is the process where an electrolyte separates into its constituent ions in a solution. The degree of dissociation, represented by Alpha in the script, is crucial for understanding how molar conductivity changes with dilution, especially for weak electrolytes, where increased dilution enhances dissociation.
💡Equilibrium Constant
The equilibrium constant, denoted as K in the script, is a measure of the extent of a chemical reaction at equilibrium. It is used to explain how changing the concentration of a weak electrolyte affects the reaction quotient (Q) and, consequently, the position of the dissociation equilibrium, leading to increased dissociation upon dilution.
💡Reaction Quotient (Q)
The reaction quotient (Q) is a measure used to predict the direction in which a reaction will proceed when it is disturbed from equilibrium. In the context of the video, Q is used to illustrate how dilution of a weak electrolyte causes Q to be less than K, shifting the equilibrium to produce more ions and thus increasing molar conductivity.
💡Infinite Dilution
Infinite dilution refers to a hypothetical state where the concentration of a solute approaches zero. The video discusses Lambda M Infinity, the molar conductivity at infinite dilution, as the y-intercept of the linear trend for strong electrolytes, representing the conductivity when the concentration is virtually nonexistent.
💡Graphical Representation
The video uses graphical representation to visualize the relationship between molar conductivity and concentration/ dilution. Plotting molar conductivity against the square root of concentration helps in fitting the data points into a straight line for strong electrolytes and a hyperbolic curve for weak electrolytes, providing a clear visual trend of how conductivity varies with concentration.
Highlights

Molar conductivity (Lambda M) is the conductivity of one mole of an electrolyte and varies with concentration.

The variation of molar conductivity with concentration depends on the type of electrolyte, whether strong or weak.

For strong electrolytes, molar conductivity increases with dilution due to complete dissociation.

Weak electrolytes show a higher increase in molar conductivity upon dilution due to increased dissociation.

Dilution of a weak electrolyte increases the degree of dissociation, represented by Alpha.

The equilibrium constant and reaction quotient are used to understand the shift in dissociation equilibrium.

The graphical representation of molar conductivity variation is crucial for understanding electrolyte behavior.

Plotting molar conductivity against the square root of concentration helps in fitting data points into a straight line.

For strong electrolytes, a linear trend is observed in the molar conductivity plot.

The slope of the line for strong electrolytes indicates the rate of increase in molar conductivity with dilution.

Weak electrolytes follow a hyperbolic curve in the molar conductivity plot, showing a more significant increase with dilution.

The molar conductivity at infinite dilution (Lambda M Infinity) is the value when concentration approaches zero.

Extrapolation of the molar conductivity line to the y-axis gives Lambda M Infinity for strong electrolytes.

The equation of the line for strong electrolytes is Lambda m = -B * sqrt(C) + Lambda M Infinity.

The graphical trends help in understanding the practical applications and theoretical implications of electrolyte behavior.

The difference in molar conductivity increase between strong and weak electrolytes is visually represented in the plot.

The video provides a comprehensive analysis of molar conductivity variation with concentration for both strong and weak electrolytes.

Transcripts

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Molar ConductivityElectrolyteConcentrationDilutionStrong ElectrolyteWeak ElectrolyteDissociationEquilibriumGraph PlottingChemical AnalysisEducational Video