Solutions

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Solutions

• CPS Chemistry

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Definitions

• Solutions
• A homogeneous mixture of two or more substances
  in a single phase
• Soluble
• Capable of being dissolved

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• Solvent
• Dissolving medium in a solution
• What is doing the dissolving
• Solute
• Substance dissolved in a solution
• What is dissolved
• Example
• Sugar in tea
• tea is solvent, sugar solute

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Types of Solutions

• May exist as gasses, liquids or solids
• One component is designated as solvent and one as
  solute
• Chart on pg. 396

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Phase

• If there are two different types of substances it
  is a phase change
• Water salt water and gas
• Same phase
• Water and apple juice
• This is an aqueous solution
• Means there is water involved
• Alcohol and liquid
• Tincture solution
• Means there is alcohol involved

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Mixtures

• 2 or more substances when each retains its
  properties
• Homogeneous
• Uniform distribution of particles
• 0.01-1nm size particles, can be atoms
• Can be physically separated
• Ex. Salt water, air
• Also called solution

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• Heterogeneous
• Distribution of particles is not uniform
• Can be separated by physical means
• Particle size 1-1000 nm (nanometer)

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Suspensions

• When particles in a solvent are so large that
  they settle out unless stirred constantly
• Gravity pulls particles to bottom of container

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• Particles gt1000nm in diameter, 1000 times as
  large as atoms
• Ex. Italian salad dressing, muddy water
• Can be separated by passing liquid through a
  filter

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Colloids

• Has particles that are intermediate in size and
  they remain dispersed in the solute
• 1-1000nm particle size
• Emulsion or foam are specific types
• Mayonnaise is an emulsion of egg and oil

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The Tyndall effect

• Is a sign that it may be a colloid
• The particles are not large enough to be seen,
  but large enough to scatter light
• Ex headlights on a foggy night

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Electrolytes vs. Nonelectrolytes

• Electrolyte
• A substance that dissolves in water to give a
  solution the ability to conduct electricity
• Nonelectrolyte
• A substance that when dissolved in water to make
  a solution that does not conduct electricity

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• When ionic compounds dissolve, the positive and
  negative ions separate from each other and are
  surrounded by water molecules
• When the ions are free to move, electricity moves
  easily

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How to Make Solutions

• You need to know the
• Solubility the maximum amount solute can
  dissolve in a solvent
• Rate how fast the solute dissolves

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Factors that affect rate of dissolution

• Surface area of the solute
• The larger the surface area, the more quickly it
  dissolves
• Agitation of a solution
• When you stir or shake the solute particles are
  dispersed throughout the solvent, and it increase
  the rate of dissolution

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Saturated Solutions

• A solution that contains the maximum amount of
  dissolved solute is saturated
• The factors that determine saturation are mass of
  solvent, mass of solute and the temperature
• When a solution contains less than the maximum
  saturation it is considered unsaturated

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Supersaturate

• A solution that contains more dissolved solute
  than a saturated solution contains under the same
  conditions
• But will form crystals when disturbed or cooled

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Like dissolves like

• The rule for predicting whether one substance
  will dissolve in another is related to the type
  of bonding, the polarity of a molecule and the
  intermolecular forces between the solute and
  solvent
• Things need to be similar for them to dissolve

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• Solvent Solute Solution
• Polar Polar yes
• Polar non-polar no
• Nonpolar Polar no
• Nonpolar Nonpolar yes

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Reminder molecule polarity
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More Vocab.

• Immiscible
• Liquid solutes and solvents that are not soluble
  in each other
• Oil and water
• Oil and salt
• Miscible
• Liquids that dissolve freely in one another in
  any proportion
• Water and food coloring

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Back to Temperature- Solubility

• Increase temp increase KE increase in
  solubility increase in rate
• Higher temps dissolve faster( Liquids)
• BUT
• Gasses act differently
• Increase temp decrease solubility
• Because gasses will leave solution at high temps

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Pressure solubility

• There is no difference to solids or liquids, but
  with an increase in pressure it will increase the
  solubility of a gas
• For example CO2 dissolved in a solution of
  sucrose and water (soda) will come out of
  solution when the pressure is decreased (opening
  the bottle, lets the soda bubble)

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Size of the Particle rate

• Because the dissolution occurs only at the
  surface of the solute, when you crush a
  substance,
• You get a larger surface, so you increase the
  rate at which it is dissolved

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Stirring - rate

• When you agitate the solvent, you increase the
  contact with the surface of the solute
• You increase the rate

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Amount of Solute -rate

• As you increase the amount of solute you want to
  dissolve
• You decrease the solubility and rate

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Concentration

• A measure of the amount of solute in a given
  amount of solvent or soulution
• MATH IS INVOLVED

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Molarity

• The number of moles of solute in one liter of
  solution
• Molar mass- as a reminder it is the mass listed
  on the PTE.. If it is for a compound, you simly
  add the masses of the atoms of the emperical
  formula
• Ex. H2O H1.00 O15.99 total molar mass is
  1.001.0015.99 17.99g

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Formula

• Amount of solute (mol)
• Molarity ( M) ______________________
• Volume of solution (L)

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Practice

• You have3.50 L of solution that contains 90.0 g
  of sodium chloride, NaCl. What is the molarity
  of that soulution?
• Mass of solute 90.0
• Solution volume 3.50 L
• Molar Mass if NaCl 58.44 g/mol

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Molality

• Dont confuse them
• The concentration of a solution expressed in
  moles of solute per kilogram of solvent
• You measure the mass of the solvent

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Formula

• moles of solute (mol)
• Molality ______________________
• mass of solvent (Kg)

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Practice

• A solution was prepared by dissolving 17.1 g of
  sucrose C12H22O11 in 125g of water. Find the
  molal concentration
• Given Solute mass 17.1g sucrose
• Solvent mass 125 g H2O

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Colligative Properties

• Boiling- point elevation
• Freezing-point depression
• Vapor-pressure lowering
• Osmotic pressure

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• These change in relation to the total number of
  solute particles present
• They are a constant that can be used to calculate
  the changes in solvents that contain nonvolatile
  solutes
• Electrolytes have greater affects on colligative
  properties