Physical Properties of Solutions
General Chemistry, 4th Ed.”, Hill, Petrucci, McCreary, and Perry (ISBN 0-13-
12.1 Types of solutions.
A solution is made up of a solute (the minor constituent)
and a solvent (the major constituent).
Solutions must be one phase, in other
words you should not be able to detect more that one phase.
The most common
solution is a solid solute (sugar) in liquid solvent (water) to give a liquid solution,
but nearly every combination of phases is possible, Refer to table 12.1
12.2 Solution concentration:
A quantitative measure of the amount of solute
dissolved, aka “strength of solution” can be Molarity, Percent by Mass, Percent
by Volume, Mass/Volume Percent.
Molarity you are suppose to know already.
Here are some useful units to use in dimensional analysis with these problems.
moles of solute/liter of solution
grams of solute/grams of solution
mL of solute/ 100 mL of solution
grams of solute/ 100 mL of solution
also popular is mg solute/dL
Scientist use M, practical people use mass%, booze hounds uses volume%, and
doctor’s use mass/volume%.
Figuring solution strength or coverting from one
type of solution strength to another is just dimensional analysis.
Problem: 24, 23, 26,27
If you are an analytical chemist or work for the EPA where trace amounts
count, then parts-per-million (ppm), parts-per-billion (ppb), and parts-per-trillion
(ppt) are used.
The general unit is mass solute per one million that amount of
Liquid solutions are so dilute that the density of the solutions is
close enough to pure water to say mL solution = 1 gram of solution.
definitions for dimensional analysis become
ppt – ηg/L
DP always just remembers the mL version then converts when necessary.
Problems: 29, 30, 31
Molality is an interesting bird.
It is defined by mass of solute per kg solvent.
label for it is m, pronounced “little m”.
People get molarity pronounced “Big M”
confused with molality or little m.
The main difference is that little m is
independent of volume changes of solution which usually come with a change in
Molality gets used when freezing point depression is calculated.
You should be able to calculate both m, and M given enough data.
Problems: 33, 35, 36
Mole fraction and mole % come into play when calculating vapor pressures of
Mole fraction, pronounced “little x”, is the moles of one species divided