types of mixtures, rates of solubility, and molarity/molality
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Types of Mixtures, Rates of Solubility, and Molarity/Molality
Solutions
SolutionsSoluble – capable of being dissolvedSolution – homogeneous mixture of two or
more substances in a single phaseComponents of Solutions
Solvent – dissolving medium in a solution Solute – substance dissolved in a solution
Types of Solutions
May exist in all states of matter (gas, liquid, solid)Examples:
Oxygen and Nitrogen gas (gas/gas)Carbon Dioxide in water (gas/liquid)Water in air (Liquid/gas)Alcohol in water (Liquid/Liquid)Mercury in Silver (Liquid/Solid)Sugar in water (solid/liquid)Copper in Nickel (Solid/Solid)
Types of Mixtures
Suspensions – particles in a solvent are so large that they settle out unless the mixture is constantly stirred or agitated
Colloids – particles that are intermediate in size between those in solutions and suspensions form mixtures known as colloidal dispersionsTyndall Effect
Particles are sometimes large enough to scatter light.
Light is scattered by colloidal particles dispersed in a transparent mediumGelatin in water = colloidSugar and water = true solution
Types of Solutions
Tyndall Effect
Solutes: Electrolytes v. NonelectrolytesElectrolyte – substance that
dissolves in water to give a solution that conducts electric current
Nonelectrolyte – substances that dissolves in water to give a solution that does not conducts electric current
Types of Solutions
Factors Affect the Rate of DissolutionIncreasing the Surface Area of SoluteAgitating a SolutionHeating a Solvent
The Solution Process
SolubilitySolution equilibrium – the physical state in
which the opposing processes of dissolution and crystallization of a solute occur at equal rates.
Saturated v UnsaturatedSaturated - solution that contains the
maximum amount of a dissolved solute Unsaturated – solution that contains less
solute than a saturated solution under the existing conditions
The Solution Process
SupersaturatedA solution that contains
more dissolved solute than a saturated solution contains under the same conditions
Solubility ValuesThe solubility of a
substance is the amount of that substance required to form a saturated solution with specific amount of solvent at a specified temperature
The Solution Process
Solute – Solvent InteractionsDissolving Ionic Compounds in Aqueous
SolutionHydration – solution process with water as
the solvent is referredWhen crystallized from aqueous solutions,
some ionic substances form crystals that incorporate water molecules.
The Solution Process
Nonpolar SolventsIonic compounds are generally not soluble in
nonpolar solvents such as carbon tetrachloride.
Non polar solvent molecules do not attract the ions of the crystal strongly enough to overcome the forces holding them together.
The Solution Process
Liquid Solutes and SolventsImmiscible – liquid solutes and solvents that
are not soluble in each otherMiscible – liquids that dissolve freely in one
another in any proportion
The Solution Process
Effects of Pressure on SolubilityIncreases in pressure increase gas
solubilities in liquidsHenry’s Law – the solubility of a gas in a
liquid is directly proportional to the partial pressure of that gas on the surface of the liquid.There are no gas bubbles in an unopened bottle of
soda because the pressure of CO2 applied during the bottling process keeps the carbon dioxide gas dissolved in the liquid.
Effervescence – rapid escape of a gas from a liquid in which it is dissolved
The Solution Process
Effects of Temperature on SolubilityIncreasing the temperature usually
decreases gas solubilityThe effect of temperature on the solubility of
solids in liquids is more difficult to predict.Often increasing the temperature increases the
solubility of solidsHowever, an equivalent temperature increase can
result in a large increase in solubility in one case and only a slight increase in another.
The Solution Process
Heats of SolutionThe net amount of heat energy absorbed or
released when a specific amount of solute dissolves
The Solution Process
Concentration – a measure of the amount of solute in a given amount of solvent or solution
Concentration of Solutions
Molarity The number of moles of solute in one liter of solution
Molarity (M) = Example: You have 3.50 L of solution that containes
90.0 g of sodium chloride. What is the molarity of that solution?Given: solute mass = 90.0n g NaCl
solution volume = 3.50 L
90.0 g NaCl x = 1.54 mol NaCl
= 0.440 M NaCl
Concentration of Solutions
Now You TryYou have 0.8 L if 0.5 M HCl solution. How
many moles of HCl does this solution contain?
To produce 40.0 g of silver chromate, you will need at least 23.4 g of potassium chromate in solution as a reactant. All you have on hand in the stock room is 5 L of a 6.0 M K2CrO4 solution. What volume of the solution is needed to give you the 23. 4 g K2CrO4 needed for the reaction?
Concentration of Solutions
What is the molarity of a solution composed of 5. 85 g of potassium iodide, KI, dissolved in enough water to make 0.125 L of solution?
How many moles of H2SO4 are present in 0.500 L ov a 0.150 M H2SO4 solution?
What volume of 3.00 M NaCl is needed for a reaction that requires 146.3 g of NaCl?
Concentration of Solutions
MolalityThe concentration of a solution expressed in
moles of solute per kilogram of solventMolality =
Concentration of Solutions
Example: A solution was prepared by dissolving 17.1 g of sucrose ( C12H22O11) in 125 g of water. Find the molal concentration of this solution.Given: solute mass = 17.1 g sucrose
Solvent mass = 125 g water 17.1 g C12H22O11 x = 0.0500 mol C12H22O11
= 0.400 m C12H22O11
Concentration of Solutions
Now You Try!A solution of iodine, I2, in carbon
tetrachloride is used when iodine is needed for certain chemical tests. How much iodine must be added to prepare a 0.480 m solution of iodine in carbon tetrachloride if 100.0 g of CCl4 is used?
What is the molality of a solution composed of 255 g of acetone, (CH3)2CO, dissolved in 200 g of water?
What quantity in grams of methanol, CH3OH, is required to prepare a 0.244 m solution in 400 g of water?
Concentration of Solutions