Solutions

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Solutions

• Aqueous Solutions

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Review

• How do ionic and molecular compounds differ?
• The molecules in molecular compounds are
  electrically neutral, covalently bonded groups of
  atoms that behave as a unit. Ionic compounds are
  huge collections of cations and anions.

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Reivew

• What is a cation?
• A positive ion
• What is an anion?
• A negative ion
• Why are ionic compounds generally soluble in
  water?
• The cations and anions are attracted to the
  charged ends of polar H2O molecules.

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Solvents and Solutes

• Aqueous solution
• A solution in which the solvent is water
• Solvent
• The dissolving medium in a solution
• Solute
• The dissolved particles in a solution

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Solvents and Solutes

• What are some of the properties of solutions?
• They are stable (they dont settle out over time)
• Particles/ion are less than 0.1 nanometers in
  diameter
• They cannot be separated by filtration

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The Solution Process

• Solvation
• A process that occurs when an ionic solute
  dissolves
• In solution, the ions are surrounded by solvent
  molecules
• What is meant by like dissolves like?
• This refers to the polarity of the compounds

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Electrolytes and Nonelectrolytes

• Electrolytes
• A compound that conducts an electrical current in
  aqueous solution or in the molten state
• All ionic compounds are electrolytes, but most
  covalent compounds are not
• Some polar covalent compounds form polyatomic
  ions when dissolved in water
• These compounds are electrolytes

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Electrolytes and Nonelectrolytes

• Nonelectrolytes
• A compound that does not conduct an electric
  current in aqueous solution or in the molten
  state
• Weak electrolytes
• A solution in which only a fraction of the solute
  exists as ions.
• Strong electrolytes
• A solution in which a large portion of the solute
  exists as ions.

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Water of Hydration

• Water of hydration
• Water molecules that are an integral part of a
  crystalline structure
• Written as (ionic formula unit)H2O
• The tells you how many water molecules per
  ionic formula unit
• If the water is there it is called a hydrate. If
  the water is not there (when it usually is) it is
  called the anhydrate. The two forms often have
  different colors.

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Water of Hydration

• Effloresce
• To lose the water of hydration
• Hydroscopic
• A term describing compounds that remove water
  from the air
• Desiccant
• A hydroscopic substance used as a drying agent
• Deliquescent
• A term describing a substance that removes enough
  water from the air to form a solution

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Water of Hydration

• You can use the formula of a a hydrate to
  calculate its percent by mass water.

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Water of Hydration

• Example Calculate the percent mass of water in
  Epsom salt, MgSO47H2O

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Heterogeneous Aqueous Solutions

• What is a heterogeneous mixture?
• One with different parts, like sand in water

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Suspensions

• Suspensions
• A mixture from which some of particles settle out
  slowly upon standing
• Muddy water
• The particles are about 100 nm in diameter and
  can be filtered out

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Colloids

• Colloid
• A mixture whose particles are intermediate in
  size between those of a suspension and a solution
• These cannot be filtered
• Jello is a colliod.

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Colloids

• Dispersed phase
• The particles in a colloid
• Usually between 0.1 nm and 100 nm in diameter
• Dispersing medium
• The substance a colloid is made in

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Colloids

• Tyndall effect
• Scattering of light by particles in a colloid or
  suspension, which causes the beam to become
  visible
• Brownian motion
• The chaotic movement of colloidal particles,
  caused by collision with particles of the
  dispersing medium

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Colloids

• Emulsions
• Colloids of liquids in liquids (like shaking oil
  and vinegar to mix them together)
• Adding an emulsifier makes the emulsion stable
• Add flour to oil and water to make gravy
• Add parmesan cheese to butter and cream to make
  Alfredo sauce
• Add egg yolk to oil and vinegar to make mayonnaise