solubility and concentration
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Solubility and Concentration. Chemistry Mrs. Coyle. Part I Solubility:. The ability of a solute to dissolve in a solvent. Expressed as g solute/100g H 2 O or g solute/100mL H 2 O . Soluble. • Soluble: a solute that has appreciable solubility. Miscible. - PowerPoint PPT PresentationTRANSCRIPT
Solubility and Concentration
ChemistryMrs. Coyle
Part I Solubility:
The ability of a solute to dissolve in a solvent.
Expressed as g solute/100g H2O
or g solute/100mL H2O
Soluble
• Soluble: a solute that has appreciable solubility.
Miscible
Substances that dissolve in each other.
Solubility Curves
Precipitate: solute that comes out of solution.•
Types of Solutions Saturated contains the maximum amount of
solute that can be dissolved at the given conditions of T and P.
Unsaturated contains less than the saturated amount of solute.
Supersaturated contains more than the saturated amount of solute by dissolving at higher temp and then cooling.
A supersaturated solution crystallizes after a seed crystal is introduced.
http://www.chem.ufl.edu/~itl/2045/change/C12F11.GIF
Rates of Solution
Does every candy you eat take the same time to dissolve?
Factors affecting the rate of dissolving:
Surface Area
Stirring
Temperature (average kinetic energy)
Factors Affecting Solubility
Temperature (affects solid, liquid and gaseous solutes)
Pressure (affects gaseous solutes)
Effect of temperature on solubility of gases.Example:
Compare the amount of oxygen dissolved in the waters of the arctic ocean to the amount of oxygen dissolved in warm tropical waters.
Effect of temperature on solubility of solids. Example:
Can you dissolve more sugar in warm water or in cold water?
Solubility Curves
Effect of Pressure on solubility of solids. Negligible.
Effect of Pressure on solubility of gases. Henry’s Law: the amount of gas dissolved in
a solution is directly proportional to the pressure of the gas above the solution.
The higher the pressure the higher the solubility of the gas.
Effect of Pressure on solubility of gases.
http://www.chem.ufl.edu/~itl/2045/lectures/lec_i.html
Example
An unopened bottle of soda has a pressure of 5atm above the liquid, so the concentration of CO2 in the soda is high.
Compare that to a pressure of 1 atm above the liquid when the bottle has been opened.
Part II Concentration: A measure of the amount of solute dissolved in
the solution. Molarity (M) Molality (m) Mole Fraction (x) Percent by Mass (%)
Part II
Concentration
Molarity• A unit of concentration of a solution
expressed in moles solute per liter of solution. (Note: 1L = 1 dm3)
Molarity (M) =Moles of Solute
Liters of Solution
Why Molarity ?
http://www.chem.ucla.edu/~gchemlab/volumetric_soln_conc.jpg
Steps involved in the preparation of a standard aqueous solution
Process of making 500 mL of a1.00 M acetic acid solution
Ex. 1 Molarity
What is the molarity of a solution of 8g NaOH in 100mL of solution?
Answer: 2M NaOH
Ex. 2 Molarity
How many grams of NaOH are contained in 2L of a 3M NaOH solution?
Answer: 240g NaOH
Making Dilutions
Moles Solute=M1V1=M2V2
M molarity V volume
Ex. 3 Dilutions
How many milliliters of 2.00M MgSO4 solution must be diluted with water to prepare 100.00 mL of 0.400M MgSO4?
Answer: 20.0mL
Percent by Mass
% by mass= Mass of solute x 100 % Mass of solution
Percent by Volume
% by volume= Volume of solute x 100 % Volume of solution
Part III Molality and Mole Fraction
Molality
Moles of Solute per kilogram of Solvent
Molality (m) = moles solute kg solvent
Mole Fraction
xsolute = Moles of solute Moles of solution
xsolvent = Moles of solvent Moles of solution
xsolute + xsolvent= 1