Solubility Equilibria Flashcards

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Questions and Answers

What are sparingly soluble salts?

Salts that dissociate partially in the solution into their constituent ions.

What is the definition of solubility of a salt?

It is the concentration of the salt which refers to the maximum amount of the solute that can be dissolved in 1 dm^3 of solvent to make a saturated solution at a given temperature.

What does saturated solution mean?

It means if I were to dissolve 1 more unit of solute in the water, it cannot dissolve anymore.

What is solubility measured as?

Mol dm^-3. Signup and view all the answers

What is the definition of Ksp?

An equilibrium constant which is the product of the molar concentrations of the dissolved dissociated ions (each raised to its appropriate power) in a saturated solution of the salt at a given temperature. Signup and view all the answers

What factors affect Ksp?

Temperature; Ksp is constant at constant temperature. Signup and view all the answers

How is solubility of a salt denoted?

They are denoted as 's'. Signup and view all the answers

What is the definition of the common ion effect?

The solubility of a sparingly soluble salt is decreased in the presence of a common ion from an external source. Signup and view all the answers

What is the standard answer when asked how the addition of another salt with a common ion affects solubility?

By Le Chatelier's principle, the equilibrium position will shift to decrease the concentration of the common ion, hence solubility of the original salt will be decreased. Signup and view all the answers

What type of salts are always sparingly soluble?

Carbonates and hydroxides. Signup and view all the answers

What is complex ion formation?

The addition of a reagent that reacts with cation (anion) to form a complex ion, which increases the solubility of the sparingly soluble salt. Signup and view all the answers

What is the standard answer for the effect of complex ion formation on the solubility of the salt?

When a reagent is added, a complex ion is formed hence decreasing the common ion, shifting equilibrium to increase solubility. Signup and view all the answers

What is the trend of solubility of silver halides AgCl, AgBr, AgI down group 17?

The solubility decreases from AgCl to AgI. Signup and view all the answers

What is the observation when Cl- of AgCl is reacted with AgNO3 followed by NH3?

White ppt of AgCl soluble in excess NH3(aq). Signup and view all the answers

What is the observation when I- of AgI is reacted with AgNO3 followed by NH3?

Yellow ppt of AgI insoluble in NH3(aq). Signup and view all the answers

What is the trend of the colors of silver halides AgCl, AgBr, AgI down group 17?

The color becomes more yellow; AgCl (white), AgBr (cream), AgI (yellow). Signup and view all the answers

How is the solubility product (Ksp) of a salt related to its solubility in a solvent?

The higher the Ksp of the salt, the more likely it is soluble, as Ksp is directly proportional to solubility. Signup and view all the answers

What is the definition of ionic product?

A product of molar concentration of dissolved dissociated ions (each raised to its appropriate power) in the solution at a given temperature. Signup and view all the answers

What happens when IP = Ksp?

Saturation point: no ppt occurs. Signup and view all the answers

What happens when IP < Ksp?

Lower than saturation point: no ppt occurs. Signup and view all the answers

What happens when IP > Ksp?

Beyond saturation point: ppt occurs. Signup and view all the answers

What happens to the concentration when 2 solutions are mixed in equal volumes?

Since the total volume is doubled, the concentration is halved. Signup and view all the answers

What are the steps for solving precipitation problems involving sparingly soluble salts?

Step 1: write down the partial dissociation equation for the sparingly soluble salt. Step 2: write down the ionic product expression. Step 3: determine the new ion concentration based on solution mixing. Step 4: substitute new ion concentration into ionic product expression and evaluate, comparing with Ksp. Signup and view all the answers

Study Notes

Sparingly Soluble Salts

Sparingly soluble salts only partially dissociate in solution into ions.
Common examples include carbonates and hydroxides.

Solubility and Saturation

Solubility of a salt indicates the maximum amount that can dissolve in 1 dm³ of solvent at a given temperature, expressed in mol dm⁻³.
A saturated solution can't dissolve any more solute; adding any more will not increase concentration.

Equilibrium and Ksp

Ksp is the equilibrium constant equal to the product of the molar concentrations of dissociated ions in a saturated solution, each raised to the power of their coefficients.
Ksp remains constant at a constant temperature, making temperature a key factor affecting solubility.

Common Ion Effect

The presence of a common ion from an external source decreases the solubility of a sparingly soluble salt by shifting equilibrium to the left.
Le Chatelier's principle explains this shift, resulting in the formation of more solid salt.

Complex Ion Formation

Adding certain reagents can lead to complex ion formation, which increases the solubility of sparingly soluble salts.
When complexing agents (e.g., NH3) are introduced, they react with cations to form complex ions, reducing the concentration of the common ion and shifting equilibrium right.

Solubility Trends in Silver Halides

Solubility decreases from AgCl to AgI as you move down group 17 of the periodic table.
Color changes from white (AgCl) to cream (AgBr) to yellow (AgI).

Ionic Product (IP) and Ksp Relationship

The ionic product is determined by the concentration of dissolved ions and varies with solution conditions, unlike Ksp which is constant for a given salt at a specific temperature.
If IP equals Ksp, the solution reaches saturation without precipitation; if IP is less than Ksp, no precipitation occurs; if IP exceeds Ksp, precipitation starts.

Concentration Changes Upon Mixing Solutions

When two solutions are mixed in equal volumes, the concentration of solutes is halved due to the doubled total volume.

Steps for Solving Precipitation Problems

Write the partial dissociation equation for the sparingly soluble salt.
Derive the ionic product expression for the dissociation.
Calculate the new ion concentrations based on mixed solutions.
Substitute these concentrations into the ionic product expression and assess against Ksp to determine precipitation status.

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Description

Test your knowledge on solubility equilibria with this flashcard quiz. Learn about sparingly soluble salts and the definition of solubility in an interactive format. Perfect for reviewing key concepts in chemistry.