Chapter 6: Common ion effect | CHM 214 | 057

Jacob Stewart
11 Feb 202104:10
EducationalLearning
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TLDRThe video script discusses the common ion effect and its impact on solubility. Using mercury chloride in the presence of sodium chloride as an example, it explains how the concentration of mercury ions decreases significantly due to the presence of chloride ions from sodium chloride. The equilibrium concept and the calculation of Ksp are used to demonstrate that the solubility is lower in a solution with a shared ion, highlighting the common ion effect's importance in understanding solubility and equilibria in solutions.

Takeaways
  • 🌟 The concept of the common ion effect is introduced, which impacts the solubility of salts in a solution.
  • 🔍 Mercury chloride (HgCl2) is used as an example to discuss its solubility in water and the presence of other ions.
  • 🧪 At room temperature, the solubility of mercury in a mercury chloride solution is calculated to be 6.7 x 10^-7 molar.
  • 📉 In a 0.1 M sodium chloride (NaCl) solution, the concentration of mercury is expected to be lower due to the common ion effect.
  • 💧 The presence of chloride ions from NaCl in the solution reduces the solubility of HgCl2, as the chloride ions are already in equilibrium.
  • 🔢 The solubility product constant (Ksp) is used to calculate the concentration of mercury, considering the existing chloride concentration.
  • 📈 The calculation shows that the mercury concentration in the NaCl solution is 1.2 x 10^-18 M, significantly lower than in pure water.
  • 🔄 The common ion effect demonstrates how the presence of a shared ion can decrease the solubility of a salt.
  • 📚 Understanding the common ion effect is crucial for predicting the behavior of salts and other compounds in mixed solutions.
  • 🌊 The equilibrium in a solution is sensitive to the total concentration of ions, regardless of their source.
  • 📉 The presence of other salts in a solution can significantly alter the solubility of the salts present, a phenomenon known as the common ion effect.
Q & A

  • What is the common ion effect and how does it influence solubility?

    -The common ion effect refers to the phenomenon where the presence of an additional ion in a solution, which is common to the dissolution equilibrium of a salt, alters the solubility of that salt. It decreases the solubility of the salt because the common ion from another dissolved substance will reduce the concentration of the salt in solution, thus shifting the equilibrium to favor the undissolved form according to Le Chatelier's principle.

  • What is the role of sodium chloride in the given example with mercury chloride?

    -In the given example, sodium chloride acts as a source of the common ion, chloride, which is also produced when mercury chloride dissolves in water. The presence of chloride ions from sodium chloride suppresses the dissolution of mercury chloride, resulting in a lower concentration of mercury ions in the solution.

  • How does the presence of sodium chloride in a solution affect the concentration of mercury ions from mercury chloride?

    -The presence of sodium chloride, which provides additional chloride ions, reduces the concentration of mercury ions in the solution. This is due to the common ion effect, where the increased concentration of chloride ions shifts the solubility equilibrium of mercury chloride towards the undissolved form, resulting in a lower concentration of mercury ions.

  • What was the calculated concentration of mercury ions in a mercury chloride solution without sodium chloride?

    -The calculated concentration of mercury ions in a mercury chloride solution without sodium chloride was 6.7 times 10 to the power of negative 7 molar.

  • What is the expected concentration of mercury ions when sodium chloride is also present in the solution?

    -When sodium chloride is present in the solution, the expected concentration of mercury ions is significantly lower, at 1.2 times 10 to the power of negative 18 molar, due to the common ion effect.

  • Why does the solubility of mercury chloride decrease in the presence of sodium chloride?

    -The solubility of mercury chloride decreases in the presence of sodium chloride because the additional chloride ions from sodium chloride increase the total chloride ion concentration in the solution. This increased concentration causes the dissolution equilibrium to shift to the left, favoring the undissolved form of mercury chloride and thus reducing the concentration of mercury ions in solution.

  • How does the common ion effect impact the equilibrium of a solution?

    -The common ion effect impacts the equilibrium of a solution by increasing the concentration of a particular ion shared by a dissolved salt. This increased concentration causes the equilibrium to shift in the direction that reduces the production of that common ion, typically by decreasing the solubility of the salt in question.

  • What is the solubility product constant (Ksp) and how is it related to the common ion effect?

    -The solubility product constant (Ksp) is a value that represents the product of the molar concentrations of the ions in a saturated solution at equilibrium. The common ion effect is related to Ksp in that the presence of a common ion from another source in the solution affects the concentrations of the ions from the salt, thus altering the Ksp value and the solubility of the salt.

  • How does the concentration of mercury ions change when going from a solution with no sodium chloride to one with 0.1 M sodium chloride?

    -The concentration of mercury ions decreases significantly, from 6.7 times 10 to the power of negative 7 molar in the absence of sodium chloride to 1.2 times 10 to the power of negative 18 molar in the presence of 0.1 M sodium chloride, due to the common ion effect.

  • What is the mathematical expression for the solubility product constant (Ksp) for mercury chloride?

    -The mathematical expression for the solubility product constant (Ksp) for mercury chloride is Ksp = [Hg^2+][Cl^-], where [Hg^2+] is the molar concentration of mercury ions and [Cl^-] is the molar concentration of chloride ions in the solution.

  • How does the presence of a common ion from another salt affect the solubility of a given salt?

    -The presence of a common ion from another salt reduces the solubility of the given salt. This is because the increased concentration of the common ion shifts the dissolution equilibrium towards the undissolved form of the salt, resulting in a lower concentration of the ions from the given salt in the solution.

Outlines
00:00
🌟 Understanding the Common Ion Effect

This paragraph introduces the concept of the common ion effect and its impact on solubility. It uses the example of a mercury chloride solution to explain how the presence of additional chloride ions from a sodium chloride solution affects the equilibrium and solubility of mercury chloride. The key point is that the solubility of mercury chloride decreases significantly when chloride ions are already present in the solution due to the common ion effect, resulting in a much lower concentration of mercury compared to when the salt is dissolved in pure water.

Mindmap
Keywords
💡common ion effect
The common ion effect refers to the phenomenon where the presence of an additional ion in a solution, which is common to the dissolution equilibrium of a salt, influences the solubility of that salt. In the context of the video, when mercury chloride is dissolved in water containing sodium chloride, the chloride ions from sodium chloride suppress the solubility of mercury chloride due to their common presence. This effect is crucial in understanding solubility equilibria in complex solutions and is demonstrated in the video through the calculation of mercury concentration in different solutions.
💡equilibrium
Equilibrium in chemistry refers to a state where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. In the video, the equilibrium of mercury chloride dissolution is discussed, where the equilibrium constant (Ksp) is used to determine the solubility of mercury chloride in water. The equilibrium is affected by the common ion effect, as the presence of additional chloride ions from sodium chloride shifts the equilibrium, resulting in a lower solubility of mercury chloride.
💡Ksp
Ksp, or the solubility product constant, is a term used in chemistry to describe the equilibrium constant for the dissolution of a sparingly soluble salt. It is the product of the concentrations of the ions in a solution, each raised to the power of its coefficient in the balanced dissolution equation. In the video, the Ksp value is used to calculate the concentration of mercury ions in a solution of mercury chloride, and how this value changes when sodium chloride is added due to the common ion effect.
💡mercury chloride
Mercury chloride is a chemical compound consisting of mercury and chlorine. It is used in the video as an example to illustrate the concept of solubility and the common ion effect. The solubility of mercury chloride is affected by the presence of other ions in the solution, specifically chloride ions from sodium chloride, which demonstrates how the common ion effect impacts the equilibrium and solubility of salts.
💡sodium chloride
Sodium chloride, commonly known as table salt, is a widely used chemical compound in various applications, including scientific experiments. In the video, a 0.1 molar solution of sodium chloride is used to demonstrate the common ion effect on the solubility of mercury chloride. The presence of chloride ions from sodium chloride in the solution reduces the solubility of mercury chloride, illustrating how the presence of a common ion can affect chemical equilibria.
💡solution
In chemistry, a solution is a homogeneous mixture composed of two or more substances, where one substance, called the solute, is uniformly dispersed in another substance, known as the solvent. The video discusses solutions of mercury chloride and sodium chloride, and how the presence of ions in these solutions influences the solubility of other compounds through the common ion effect.
💡solubility
Solubility refers to the ability of a substance to dissolve in a solvent to form a homogeneous solution. It is a key concept in the video, as it is used to explain how the presence of a common ion from sodium chloride affects the solubility of mercury chloride. The video shows that the solubility of mercury chloride is significantly reduced when chloride ions are already present in the solution due to the common ion effect.
💡concentration
Concentration in chemistry refers to the amount of a particular substance present in a given volume of solution. It is typically expressed in molarity (moles per liter). In the video, the concentration of mercury ions is a central theme, with the calculation and comparison of these concentrations in different solutions illustrating the common ion effect and its impact on solubility.
💡molar
Molar refers to a unit of measurement used in chemistry to express the amount of a substance in terms of the number of molecules or entities it contains, typically one mole. It is used to describe the concentration of substances in a solution, such as the concentration of mercury ions in the video. Understanding molarity is essential for calculating solubility and understanding the common ion effect.
💡chemical equilibrium
Chemical equilibrium is a dynamic state in which the concentrations of reactants and products remain constant over time because the rates of the forward and reverse reactions are equal. In the video, the chemical equilibrium of mercury chloride dissolution is affected by the presence of sodium chloride, which alters the concentrations of mercury and chloride ions in the solution due to the common ion effect.
💡chloride ions
Chloride ions are negatively charged particles that result from the dissociation of chloride-containing compounds in solution. In the video, the presence of chloride ions from sodium chloride in the solution plays a critical role in reducing the solubility of mercury chloride due to the common ion effect. The chloride ions suppress the dissolution of mercury chloride by increasing the concentration of chloride ions in the solution, which shifts the equilibrium to favor the undissolved form of the salt.
Highlights

Discussion of the common ion effect in solutions.

Use of mercury chloride as an example to explain the common ion effect.

Equilibrium and solubility in the context of mercury chloride solution.

Calculation of mercury concentration in solution at room temperature.

Presence of sodium chloride affecting the concentration of mercury in solution.

Explanation of how chloride ions from sodium chloride impact mercury solubility.

Concept that equilibrium is concerned with the total ion concentration, regardless of source.

Recalculation of mercury concentration in the presence of 0.1 molar sodium chloride solution.

Mathematical demonstration of the decrease in mercury concentration due to the common ion effect.

Significant reduction in mercury solubility in the presence of sodium chloride.

Nine orders of magnitude decrease in mercury concentration as a result of the common ion effect.

Practical implications of the common ion effect on the solubility of salts in solutions with other present ions.

The common ion effect's impact on equilibria in chemical solutions.

Importance of understanding the common ion effect for solubility and equilibrium calculations.

Transcripts

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Chemistry PrinciplesSolubility EquilibriumCommon Ion EffectIon ConcentrationMercury ChlorideSodium ChlorideKsp CalculationEquilibrium ShiftChemical Solubility