Variation of conductivity with dilution- Part 1 | Electrochemistry | Chemistry | Khan Academy

Khan Academy India - English
15 May 202309:59
EducationalLearning
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TLDRThis video script explores the relationship between the conductivity of an electrolytic solution and the concentration of ions within it. It explains how conductivity decreases with dilution due to fewer ions available for charge transfer. The script also discusses molar conductivity, highlighting its increase with dilution for both strong and weak electrolytes, with a more significant increase for weak electrolytes due to increased dissociation. The concept is applied to water purification, where conductivity serves as an indicator of purity.

Takeaways
  • 🌊 Conductivity in an electrolytic solution is influenced by the concentration of ions present, which affects the flow of electrons.
  • πŸ” Conductivity is defined as the conductance of a unit volume and is inversely related to resistivity.
  • πŸ”Œ The resistance of a wire is given by the formula rho L over A, where rho is resistivity, L is length, and A is area.
  • πŸ’§ In solutions, the actual charge transfer is done via ions, making the concentration of ions a key factor in conductivity.
  • πŸ“‰ As the concentration of ions in a solution decreases (or dilution increases), the conductivity also decreases.
  • 🌐 The concept of conductivity varying with concentration is applied in water purification systems to monitor the purification process.
  • πŸ”¬ Molar conductivity (Ξ›m) is the conductivity on a per mole basis, defined as conductivity (Kappa) divided by molar concentration.
  • πŸ”„ Contrary to initial intuition, molar conductivity does not simply increase with decreasing concentration due to the dependency of conductivity on concentration itself.
  • πŸŒ€ For weak electrolytes, increasing dilution leads to more dissociation and thus an increase in molar conductivity.
  • πŸ’₯ For strong electrolytes, dilution reduces electrostatic interactions between fully dissociated ions, allowing them to move more freely and increasing molar conductivity.
  • πŸ“ˆ Both weak and strong electrolytes show an increase in molar conductivity with dilution, but the increase is more significant for weak electrolytes due to increased ion production.
Q & A

  • What is the primary factor affecting the conductivity of an electrolytic solution?

    -The primary factor affecting the conductivity of an electrolytic solution is the concentration of ions in the solution. The higher the concentration, the more ions are available to conduct electricity, thus increasing conductivity.

  • How is the conductivity of a solution related to the flow of electrons in a wire?

    -The conductivity of a solution is analogous to the flow of electrons in a wire. In a wire, resistance is given by resistivity (rho) times length (L) over area (A). For a solution, conductivity is the inverse of resistivity and can be thought of as the conductance of a unit volume of the solution.

  • What is the significance of the unit volume in the context of resistivity and conductivity?

    -The unit volume is significant because it allows us to define resistivity as the resistance of a unit volume of material. Similarly, conductivity, being the inverse of resistivity, represents the conductance of a unit volume of the solution.

  • How does the dilution of an electrolytic solution affect its conductivity?

    -When an electrolytic solution is diluted by adding more solvent, the concentration of ions decreases, leading to a reduction in the number of charge carriers and thus a decrease in conductivity.

  • What is the application of the relationship between conductivity and concentration in water purification systems?

    -In water purification systems, the relationship between conductivity and concentration is used to monitor the purification process. As impurities are removed and the water becomes purer, the number of ions decreases, leading to a decrease in conductivity, which can be measured to assess the purity level of the water.

  • What is molar conductivity, and how is it defined?

    -Molar conductivity, denoted by Lambda m, is defined as the conductivity (Kappa) of a solution divided by its molar concentration or molarity. It represents the conductivity on a per mole basis, indicating how well a mole of a substance conducts electricity in a solution.

  • Why does the initial assumption that molar conductivity and concentration are inversely related lead to a misunderstanding?

    -The initial assumption that molar conductivity and concentration are inversely related is misleading because conductivity itself depends on concentration. As concentration decreases, conductivity also decreases, so the relationship between molar conductivity and concentration is not as straightforward as initially thought.

  • How does the degree of dissociation of a weak electrolyte affect its molar conductivity upon dilution?

    -For a weak electrolyte, which does not dissociate completely, increasing the dilution can lead to a higher degree of dissociation, resulting in more ions being available for conduction. This means that the molar conductivity of a weak electrolyte increases upon dilution.

  • What happens to the molar conductivity of a strong electrolyte when it is diluted?

    -For a strong electrolyte, which fully dissociates into ions, dilution does not increase the number of ions since they are already at maximum. However, dilution reduces the electrostatic interactions between ions, allowing them to move more freely and thus increasing the molar conductivity.

  • How does the increase in molar conductivity upon dilution differ between weak and strong electrolytes?

    -While both weak and strong electrolytes show an increase in molar conductivity upon dilution, the increase is more significant for weak electrolytes. This is because weak electrolytes introduce more ions due to increased dissociation upon dilution, whereas strong electrolytes already have the maximum number of ions due to complete dissociation.

Outlines
00:00
πŸ”¬ Understanding Conductivity and Ion Concentration

This paragraph discusses the concept of conductivity in electrolytic solutions and how it is influenced by the concentration of ions. It explains that conductivity is the conductance of a unit volume and is directly related to the number of ions present. As the concentration of ions decreases, or the solution becomes more diluted, the ability of the solution to conduct electricity also decreases. The paragraph also touches on the practical application of this principle in water purification systems, where conductivity is used to monitor the purification process as impurities, which contribute to ion concentration, are removed.

05:02
πŸ“Š Molar Conductivity and Its Relationship with Concentration

The second paragraph delves into molar conductivity, which is defined as the conductivity per mole of an electrolyte. It clarifies a common misconception that molar conductivity and concentration are inversely related. The explanation highlights that molar conductivity actually increases with dilution for both weak and strong electrolytes, but for different reasons. For weak electrolytes, increased dilution leads to greater dissociation and thus more ions, enhancing molar conductivity. In contrast, strong electrolytes, which fully dissociate even at low concentrations, experience a reduction in electrostatic interactions between ions upon dilution, allowing them to move more freely and increasing their molar conductivity. The paragraph emphasizes that the increase in molar conductivity is more pronounced for weak electrolytes due to the additional ions produced by increased dissociation.

Mindmap
Keywords
πŸ’‘Conductivity
Conductivity refers to the ability of a material to conduct electricity, which is a central theme in the video. It is defined by the flow of electrons, facilitated by ions in the case of an electrolytic solution. The script discusses how conductivity is affected by the concentration of ions in the solution, with higher concentrations leading to greater conductivity. For example, the script mentions that 'the number of ions in the solution or the concentration of ions is an important factor that will affect the conductivity.'
πŸ’‘Charge Transfer
Charge transfer is the process by which electrons move from one point to another, and in the context of the video, it occurs via ions in an electrolytic solution. The script explains that the actual charge transfer happens through ions, making the number of ions in the solution a critical factor for conductivity. For instance, the script states, 'the actual charge transfer happens via ions the number of ions in the solution or the concentration of ions is an important factor that will affect the conductivity.'
πŸ’‘Ions
Ions are atoms or molecules that have gained or lost one or more electrons, resulting in a net electrical charge. In the script, ions are highlighted as the carriers of charge in an electrolytic solution, which directly influences the solution's conductivity. The script uses the term to explain how the decrease in ion concentration leads to a decrease in conductivity, as in 'the number of ions are decreasing the charge transfer will also decrease.'
πŸ’‘Concentration
Concentration in this context refers to the amount of solute (ions) present in a given volume of solution. The video script explains that changes in concentration directly affect the conductivity of the solution, with lower concentrations leading to lower conductivity. The script illustrates this by saying, 'if you're looking at conductivity in solutions we need to think about the concentration or the amount of ions which are present in this unit volume.'
πŸ’‘Dilution
Dilution is the process of reducing the concentration of a solute in a solution by adding more solvent. The script discusses how increasing dilution leads to a decrease in the number of ions per unit volume, which in turn reduces the solution's conductivity. An example from the script is, 'what happens when we decrease the concentration or increase the dilution... the ability of this unit volume to conduct electricity decreases.'
πŸ’‘Molar Conductivity
Molar conductivity, denoted by Lambda m in the script, is defined as the conductivity of a solution divided by its molar concentration. It represents the conductivity on a per mole basis. The script explores how molar conductivity changes with the concentration of the solution, noting that it increases with dilution for both strong and weak electrolytes. The script states, 'molar conductivity which is denoted by this Lambda m is defined so it is the conductivity Kappa divided by the molar concentration.'
πŸ’‘Molarity
Molarity is a measure of the concentration of a substance in a solution, expressed in moles per liter. The script uses molarity in the context of defining molar conductivity, which is the ratio of the solution's conductivity to its molarity. The script explains this relationship by saying, 'molar conductivity is the conductivity on a per mole basis.'
πŸ’‘Electrolytic Cell
An electrolytic cell is a device that uses electrical energy to drive a non-spontaneous chemical reaction. The script mentions the flow of electrons in such a cell, facilitated by the movement of ions in a solution. The video uses the concept of an electrolytic cell to illustrate the principles of conductivity and charge transfer, as indicated by 'in this solution of an electrolytic cell.'
πŸ’‘Water Purification
The script discusses the application of conductivity principles in water purification systems. It explains that impure water, containing more ions, has higher conductivity, while pure water, with fewer ions, has lower conductivity. This principle is used to monitor the purification process, as the script states, 'this idea is sometimes used in water purification systems so if you take some impure water, the impurities in such water are usually things like salts which are basically good electrolytes.'
πŸ’‘Dissociation
Dissociation refers to the process in which an electrolyte separates into ions when dissolved in a solvent. The script differentiates between strong and weak electrolytes based on their degree of dissociation. Strong electrolytes dissociate completely, while weak electrolytes do not. The script uses the concept of dissociation to explain how the molar conductivity of weak electrolytes increases with dilution, as it states, 'a weak electrolyte is one that does not dissociate completely.'
Highlights

Conductivity in electrolytic solutions is affected by the concentration of ions.

Charge transfer in solutions occurs via ions, making ion concentration a key factor for conductivity.

Conductivity is defined as the inverse of resistivity and represents the conductance of a unit volume.

The ability of a 1 ml solution to conduct electricity is referred to as its conductivity.

Conductivity decreases as the concentration of ions in a unit volume decreases.

Dilution of a solution leads to a decrease in the number of ions and thus a decrease in conductivity.

The relationship between conductivity and concentration is utilized in water purification systems.

Impure water with higher ion concentration has higher conductivity, while pure water has lower conductivity.

Molar conductivity (Ξ›m) is defined as conductivity (ΞΊ) divided by molar concentration.

Molar conductivity represents conductivity on a per mole basis.

The relationship between molar conductivity and concentration is not straightforward due to the dependency of conductivity on concentration.

For weak electrolytes, increasing dilution leads to more dissociation and higher molar conductivity.

For strong electrolytes, molar conductivity increases with dilution due to reduced electrostatic interactions between ions.

The increase in molar conductivity upon dilution is more significant for weak electrolytes compared to strong electrolytes.

The concept of molar conductivity helps in understanding the behavior of electrolytes in solutions and their impact on conductivity.

Monitoring changes in conductivity can indicate the level of purification in water treatment processes.

Practical applications of conductivity principles are demonstrated in the context of water purification.

Transcripts

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ConductivityIon ConcentrationElectrolytic CellsElectrical ConductanceDilution EffectWater PurificationMolar ConductivityWeak ElectrolytesStrong ElectrolytesIon DissociationElectrostatic Interaction