Transcript Solubility & Molarity Notes

Changes in Solubility
I. Pressure
A. Changes in pressure do not affect solubility of liquid or
solid solutes in liquid solvents.
1. But, increases in pressure do increase the solubility of a
gas in liquids.
II. Temperature
A. Increasing the temperature usually increases the
solubility of solids in liquids.
B. But, increasing temperature decreases the solubility of
gases in liquids.
** This is important for fish in the winter, since colder
temperature means more O2 in water which is good
since fish move less in cold water. **
Molarity
• I. Concentration of Solutions
• A. Concentration-DEF- a measure of the
amount of solute in a given amount of
solvent or solution.
• 1. There are two ways in order to express
concentration.
• a. Molarity
• b. Molality
• B. Molarity-DEF- the number of moles of
solute in one liter of solution.
• 1. In order to find the molarity of a
solution, you must know the molar mass of
the solute.
• Ex- a one molar concentration of NaOH
would be written- 1M NaOH
• 2. Formula
• Molarity (M) = amount of solute (mol)
•
volume of solution (L)
• 3. The molarity of any solution can be
calculated by dividing the number of moles
of solute by the number of liters of
solution.
• Example #1
• Ex. You have 3.5L of a solution that contains 90.0 g of
sodium chloride, NaCl. What is its molarity?
• Given: 90.0 g NaCl, 3.5 L
• ? – molarity
• You NEED moles & Liters…..so you must convert grams
to moles.
1 mol NaCl = 58.5 g NaCl (molar mass)
*
90.0 g
1 mol NaCl
58.5 g NaCl = 1.54 mol NaCl
M = mol/L so… plug in your numbers AND….
M= 1.54 mol NaCl/ 3.5 L of solution (from problem) =
0.44M NaCl (for each 1 liter of solution)
• Example #2
• Ex. You have 0.8 L of a 0.5 M HCl solution.
How many moles of HCl does this solution
contain?
• Given: 0.8 L and 0.5 M HCl
• ? – moles of HCl
• * You need to rearrange the formula for molarity
so….
• Moles = volume x molarity
• SO….
• moles= 0.8 L x 0.5 M HCl = 0.4 moles of HCl