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Unit: Acids, Bases, and Solutions

Introduction to Solutions

Day 1 - Notes

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After today, you should be able to…

Explain the differences between the three different types of solutions
Describe how to make a supersaturated solution
Describe how to increase the rate of dissolving

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A solution is a homogeneous mixture. The components are not chemically combined and retain their original properties.

Example: Sugar water – still tastes sweet

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Solutions

A solution is made up of a solute and solvent.

Solute: a dissolved substance
Solvent: the most abundant component of a solution, what does the dissolving

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Water is called the “universal solvent” because it has the ability to dissolve so many substances.

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Solutions

Recall, aqueous is a solution where water is the solvent.

Example:

NaCl_(s)⭢ Na⁺_(aq) + Cl^-_(aq)

H₂O

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Solubility

The maximum amount of solute dissolved in a particular solvent at a specific temperature.

Saturated: No more solute can dissolve
Unsaturated: More solute can dissolve
Supersaturated: More solute is dissolved than theoretically possible

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To make a supersaturated solution:

Add more solute than solubility allows
Heat the solution up
Slowly cool it down

This is a temporary and unstable state for a solution!

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Factors that affect solubility:

Temperature: most solid substances have higher solubility as temperature increases

All gas solutes have lower solubility as temperature increases

Pressure: only affects gas solutes

All gas solutes have higher solubility as pressure increases

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Solubility Curves

For Solid Solutes:

For Gas Solutes:

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Rate of dissolving: How fast a solute dissolves in a solvent – not to be confused with how much.

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Rate can be increased by:

Increasing temperature- There is more kinetic energy available to meet the activation energy (energy available for dissolving)
Stirring- Increases the interaction between solute and solvent
Powdering- Increase surface area of the solute which increases the interaction between solute and solvent

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Liquid-Liquid Solutions

Miscible: two liquids which uniformly mix together (ex: milk and water)

Immiscible: two liquids which will not mix, forms two layers (ex: oil and water)

Non-polar + non-polar = miscible

Polar + Polar = miscible

Non-polar + Polar = immiscible

As a general rule: “Like dissolves like”

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Concentration

Indicates the amount of solute dissolved in a given quantity of solvent.

Dilute: a small amount of solute
Concentrated: a large amount of solute

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Questions?

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