7. Aqueous Solutions

Question 1

What is a Solution

Answer 1

A homogenous mixture of two or more substances

Question 2

Heterogenous vs. Homogenous

Answer 2

Homogeneous mixture:

• A mixture with a uniform composition throughout (looks the same everywhere).
• Example: Salt dissolved in water.

Heterogeneous mixture:

• A mixture with a non-uniform composition, where you can see different parts.
• Example: Salad or sand and iron filings.

Question 3

Describe the Process of Dissolving

Answer 3

1. Forces between solute particles must be overcome
2. Forces between solvent particles must be overcome
3. Forces form between the solute and solvent particles

• Note: The attractive forces between the solute and solvent must be of similar strength to those between the solute-solute and solvent-solvent in order to overcome them.

Question 4

What is Precipitation

Answer 4

A chemical reaction where a solid forms from a solution. This solid is called a precipitate.

Question 5

What is the Rate of Dissolution

Answer 5

The rate of dissolution is the speed at which a solute dissolves in a solvent to form a solution. It describes how quickly the solute particles break apart and spread evenly throughout the liquid. This process is influenced by factors such as temperature, stirring, the size of the solute particles, the concentration of the solution, and the nature of both the solute and solvent. Warmer temperatures, agitation, and smaller solute particles generally increase the rate at which dissolution occurs.

Question 6

Describe the Process of Dissolving in regards to Solids / Precipitate

Answer 6

1. Solid begins to dissolve
2. Solid continues to dissolve, precipitation begins to occur.

• Rate of dissolution > rate of precipitations

3. Saturation Point

• Rate of dissolution = rate of precipitations.

Question 7

What is Dissolution

Answer 7

Dissolution is the process by which a solute dissolves in a solvent to form a solution. During dissolution, the particles of the solute break apart and spread evenly throughout the solvent, becoming surrounded by solvent particles. This creates a uniform mixture where the solute is no longer visible, and the composition is the same throughout.

Question 8

What is Solubility

Answer 8

Solubility refers to the maximum amount of a solute that can dissolve in a specific quantity of solvent (commonly 100g of water) at a particular temperature. It is measured in grams of solute per 100g of solvent.

Question 9

What is an Unsaturated Solution

Answer 9

Contains less solute than what can be dissolved at a specific temperature. More solute can still dissolve.

Question 10

What is a Saturated Solution

Answer 10

Contains the maximum amount of solute that can be dissolved at that temperature. Any additional solute will remain undissolved.

Question 11

What is a Supersaturated Solution

Answer 11

Contains more solute than is normally possible at that temperature. This solution is unstable; if disturbed or if a seed crystal is added, excess solute will crystallize out.

Question 12

How to Interpret a Solubility Curve

Answer 12

Outline how to interpret a solubility curve:
(Pearson pg 370)

• Solubility curves graph the relationship between solubility (y-axis) and temperature (x-axis) for various substances. These are used to determine:
  • The amount of solute that can dissolve at a given temperature.
  • Whether a solution is saturated, unsaturated, or supersaturated.

On the curve: The solution is saturated.

Below the curve: The solution is unsaturated.

Above the curve: The solution is supersaturated.

For most solids: Solubility increases with temperature.