Solutions and Mixtures
Aqueous Solutions pg. 292
•Something is dissolved in water…the something can vary.
•When compounds dissolve in water, it means that they break apart into the ions that make them up. The only covalent compounds that do this are acids. Ionic compounds dissolve in water easily.
•Example of ionic equation
What are solutions?
Solutions are homogeneous mixtures containing two or more substances called the solute and the solvent.
Solute: dissolves (less)Solvent: dissolving medium (more)
Solutions Vocabulary
Soluble: able to be dissolved in a solvent
Insoluble: unable to be dissolved in a solvent
Immiscible: two liquids that cannot dissolve or mix (oil and water)
Miscible: two liquids that are soluble in each other
SolvationWhen a solution forms, solute particles
separate from one another and the solute and solvent particles must mix. The solvent particles completely surround the surface of the solute, pull them apart, and surround the solute particles.
Solvation: process of solvent particles surrounding the solute particles forming a solution.
“Like dissolves like.”
To determine whether a solvent and solute are alike, you must examine the bonding and the polarity of the particles and the intermolecular forces between particles.
These properties affect solvation, the process of forming a solution.
Factors Affecting Rate of Solvation
Solute and solvent particles coming in contact with each other is KEY in forming a solution. Increasing the contact will increase the formation of the solution.
3 ways to increase contact or collisions:1. Agitating the mixture2. Increasing the surface area of the solute3. Increasing the temperature of the
solvent
Solubility
Maximum amount of solute that will dissolve in a solvent at a particular temperature and pressureSaturated: contains max. amount at that
T&PUnsaturated: contains less than max.
amount at that T&PSupersaturated: contains more than max.
amount at that T&P HUH?
Temperature and Pressure
HIGH temperature: at very high temperatures, more solid solute can dissolve in a liquid solvent. [supersaturated solutions start this way]
HIGH pressure: at high pressures, more gaseous solute can dissolve in a liquid solvent. [soft drinks are made this way]
Solubility Chart
Concentration of Solutions
The concentration of a solution is a measure of how much solute is dissolved in a specific amount of solvent or solution.
Molarity: most common units of solution concentration; # of moles solute dissolved in one liter of the solution
Molarity Calculations
Molarity: moles of solute liter of solution
If given grams, remember to change it to moles.
Stop
Practical Stuff: Making a Solution
If given a stronger solution, you can dilute it (water it down) to make the weaker solution that you want.
Diluting Solutions
Beaker #1 contains concentrated salt water, 2M NaCl. I want to dilute it. What do I do?
Add more water…in other words, add more solvent.
TO DILUTE A SOLUTION, ADD MORE SOLVENT.
Diluting Solutions
Does adding solvent affect the amount of solute in the solution?
NO
Diluting Solutions
If you already have a solution molarity, but you want a different molarity:
USE THIS EQUATION: M1V1 = M2V2
Sample Calculation
I have 500.0mL of a 2M NaCl solution, but I want a 1M NaCl solution. How much watershould I add?
Sample Calculations
I want 0.50L of a 0.300M CaCl2
solution, but I have a 2.00M CaCl2 solution. How much of the 2.00M CaCl2 solution is needed?
Practice
Notes: Practice Problems.
Molality
Another unit for concentrationm=moles of solute per kilogram
of solvent
Colligative Properties
Physical properties of solutions that change depending on the number of solute particles in solutionVapor pressure loweringBoiling point elevationFreezing point depression*
Reactions that form Precipitates pg. 292-293 When solutions of sodium hydroxide and
copper(II) chloride are mixed, a precipitate forms…copper(II) hydroxide.
What does solutions of sodium hydroxide and copper(II) chloride mean?
So the ionic compounds fall apart…and the copper and hydroxide ions come together to form the solid copper(II) hydroxide.
The sodium and chloride ions remain dissolved.
Ionic Equations pg. 293
Ionic equations show all the particles in a solution dissolved as ions.
Complete ionic equations show all ions and precipitates.
Net ionic equations show only how the precipitate came to form…all spectator ions are removed.
Example