Solutions

Question 1

If there are 8 M of NaCl that completely dissociates into 4 L of water, what is the concentration of the solutes in water?

Answer 1

4 M of solutes in water.

Question 2

What is K_sp?

Answer 2

K_sp is the solubility product constant and is the saturation point of a compound. The saturation point (K_sp) (a.k.a. equilibrium) is where the rate of dissociation = the rate of precipitation.

• It is similar to K_eq in the fact that it is products over reactants. The coefficient will become the exponent and the coefficient in the equation.
• Pure solids and liquids do not appear in the “K” (K_eq, K_sp, etc…) constants’ equations.

Question 3

How does temperature affect K_sp?

Answer 3

Increasing the temperature increases K_sp and decreasing the temperature decreases K_sp.

• Temperature and K_sp are directly related.

Question 4

What is the Ion product and what is its purpose?

Answer 4

The ion product’s purpose is to relate the current solubility state of a system to the system’s equilibrium. Ion product is calculated the exact same way as K_sp.

1. If the ion product is below K_sp, the solution is designated as unsaturated
2. If the ion product is equal to K_sp, the solution is designated as saturated.
3. If the ion product is above K_sp, the solution is designated as supersaturated. (Precipitate will form until the solution returns to saturation (K_sp).

• Ion product is analogous to reaction quotient (Q) during equilibriums.

Question 5

Solid NaCl is dissolved in pure H₂O and the molar solubility of NaCl is calculated. If later, solid NaCl is dissolved in a new solution already containing chloride ions, the new molar solubility of NaCl will be:

A. Lower

B. Remain the same

C. Higher

Answer 5

The new molar solubility of NaCl will be lower.

The common ion effect inhibits ion dissociation and therefore decreases the molar solubility of a compound. The Ksp, however, remains the same provided that the temperature and pressure (if gasses are involved) remain the same as well.

Question 6

What is the common ion effect?

Answer 6

Solubility of a salt is reduced by the presence of one of its constituent ions in a solution.

• Ex: If an ion is already dissolved in solution (AgNO3₎, adding more of that ion (AgCl) will not allow as much of it to dissolve as if it were added separately.
• Will not change K_sp but will change the molar solubility.

Question 7

What is the saturation point?

Answer 7

The saturation point (also known as K_sp) is the rate at which an ionic compound’s dissociation in solution is equal to the rate of precipitation out of solution.

Question 8

What is K_f?

Answer 8

K_f is the formation constant at which gives the strength of reagent interactions that form complexes.

• Simplified, it is the constant that describes how easy two or more atoms form a complex.