solvation in the process that occurs when a solute...
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November 22, 2016
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Solvents and Solutes
Water containing dissolved substances in it is called an aqueous solution also called a homogeneous mixture
In a solution, the dissolving medium is called the solvent and the substance that is dissolved in the solvent is called the solute
~solute particles have average diameters of less than 1 nm
~solute particles don't settle out upon standing
~solute particles pass through filter paper
~solute particles can be ionic or molecular
Solvents and solutes may be gases, liquids or solids
Sample solutionscarbon dioxide in water ( soda water )acetic acid in water ( vinegar )water vapor in air ( moist air )copper in silver ( sterling silver ) salt in water ( salt water )CO2 and O2 in nitrogen ( air )
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Solvation in the process that occurs when a solute dissolves. The negative and politive ions become surrounded by solvent molecules ( they become "solvated")
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Some ionic compounds cannot be solvated to any significant extent because the attractions between the ions are greater than the attractions exerted by water. These compounds are nearly insoluble.
Examples are Barium sulfate and calcium carbonate
Like dissolves likepolar solvents dissolve ionic compounds and polar molecules
nonpolar solvents dissolve non polar compounds
Polar molecules will mix to form solutions Nonpolar molecules will form solutions.However, a polar and nonpolar combination will not form a solution.Water is a polar molecule and oil is a nonpolar molecule. Thus they won't form a solution. On the other hand, since alcohol is a polar molecule, it will form a solution with water.
Therefore:
Nov 2910:10 AM
Electrolyte a substance that is in solution as ions
a strong electrolyte is completely ionized
a weak electrolyte is only partially ionized
~All ionic compounds are electrolytes.
~electrolytes conduct electricity both in solution and in the molten state.If a compound is insoluble (such as barium sulfate) it conducts electriciy in the molten state only
Nonelectrolytes are compounds that do not conduct electricity in either aqueous or molten state
~ many molecular compounds are nonelectrolytes ( because they are not made up of ions)
~ Some very polar molecular compounds are nonelectrolytes in the pure state but become electrolytes when they dissolve in water
~this happens because they ionize when they dissolve in water
EXAMPLES:Neither NH3 nor HCl are electrolytes in the pure state, but they both ionize when dissolved in water
NH3 + H2O > NH4+ + OH
HCl + H2O > H3O+ + Cl
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November 22, 2016
Dec 411:03 AM
hygroscopic substances are used as drying agents or desiccanats.
Ex silica gel is used to maintain a dry atmosphere in food packages or electonic equipment
another example: some people put rice in salt shakers to keep the salt from absorbing moisture
deliquescent compounds are so hygroscopic that they become wet when exposed to normally moist air. They remove enough water from the air to dissolve completely and form solutions
http://www.answers.com/topic/hygroscopy
Dec 411:15 AM
Suspensions and Colloids (heterogeneous mixtures)Suspensions particles settle out upon standing
Colliods particles do not settle out upon standingExamples: milk, fog, dust in air, blood, aerosol sprays, paint, smoke
~particles are larger ( greater than 100 nm ) than solution particles
~particles are intermediate between solutions and suspensions
~ particles can be filtered out
~particles cannot be filtered out
~Both colloids and suspensions exhibit the tyndall effect which is scattering of visible light in all directions. It causes the beam to be visible~solutions do not
In the tyndall effect, the beam of light is visible because the particles in colloids and suspensions scatter light.
Brownian motion random movement of colloidal particles caused by collisions of the water molecules of the medium with the colloidal particles. These collisions prevent the particles from settling out.
NOT Solutions
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November 22, 2016
Dec 41:20 PM
Emulsions colliodal dispersions of liquids in liquids that do not ordinarily mix with each other. An emulsifying agent is needed to keep the liquids stable.
Soaps are emulsifying agents because they allow two liquids that are not soluble in each other to mix and form an emulsion.
Soap has the ability to do this because it has large molecules that are polar on one end and nonpolar on the other. The polar end is attracted to water molecules and the other (nonpolar) end is soluble in oil and grease.
Example:
Mayonnaise is an emulsion, which is a mixture of two liquids that normally can't be combined. Combining oil and water is the classic example. Emulsifying is done by slowly adding one ingredient to another while simultaneously mixing rapidly. This disperses and suspends tiny droplets of one liquid through another. However, the two liquids would quickly separate again if an emulsifier were not added. Emulsifiers are liaisons between the two liquids and serve to stabilize the mixture. Eggs and gelatin are among the foods that contain emulsifiers. In mayonnaise, the emulsifier is egg yolk, which contains lecithin, a fat emulsifier.
http://www.understandingfoodadditives.org/pages/Ch2p22.htmThis link has a good explanation of emulsions and has an animation
Dec 510:09 AM
The properties of ethanol stem primarily from the presence of its hydroxyl group and the shortness of its carbon chain. Ethanol's hydroxyl group is able to participate in hydrogen bonding, rendering it more viscous and less volatile than less polar organic compounds of similar molecular weight. Ethanol, like most shortchain alcohols, is flammable, colorless, has a strong odor, and is volatile.Hydrogen bonding causes pure ethanol to be hygroscopic to the extent that it readily absorbs water from the air. The polar nature of the hydroxyl group causes ethanol to dissolve many ionic compounds. Because the ethanol molecule also has a nonpolar end, it also dissolves nonpolar substances, including most essential oils as well as numerous flavoring, coloring, and medicinal agents.
Ethanol also known as ethyl alcohol, drinking alcohol or grain alcohol
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Ksp solubility product constant
For PbI2 in water Ksp = 8.5 x 109 at 25 C
The product of the concentrations of dissolved ions. The higher the Ksp, the more soluble the substance is.
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November 22, 2016
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Clicker Practice
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a
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November 22, 2016
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1. The number of mole of aluminum nitrate which must be added to water to form 2.00L of 0.30 M nitrate ions is
a) 0.60 mol
b) 0.20 mol
c) 2.4 mol
d) 8.0 mol
Jan 54:32 PM
2. When an ionic salt dissolves in water, the solutesolvent interaction is
a) hydrogen bonding
b) LDF
c) ionion forces
d) iondipole forces
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November 22, 2016
Jan 54:33 PM
3. When a polar molecule dissolves in water, the solute solvent interaction is
a) hydrogen bonding
b) LDF
c) dipoledipole forces
d) either A or C
Jan 54:34 PM
4. Distillation separates molecules based on differences in a) solubility
b) boiling points
c) freezing points
d) conductivity
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November 22, 2016
Jan 54:36 PM
6. How much 12.0 M HCl must be used to prepare 2 L of 3.0M HCl solution?
a) 250 mL
b) 50 mL
c) 500.0 mL
d) 100 mL
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7. In column chromatography, the first substance eluted
a) has a high affinity for the mobile phase
b) is insoluble in the mobile phase
c) precipitates out of the mobile phase
d) moves more slowly through the stationary phase than other substances in solution
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November 22, 2016
Jan 54:41 PM
8.Which of the following pairs of compounds will not form a homogeneous solution?
a) sodium chloride and water
b) sodium chloride and mineral oil
c) water and ethanol
d) water and sucrose
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10. A small amount of copper is added to silver to form sterling silver. This is a) a chemical reaction because the metal atoms bond with each other
b) a solution formation, with copper as the solvent and silver as the solute
c) a solution formation , with silver as the solvent and copper as the solute
d) a chemical reaction because the metals will exchange electrons
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November 22, 2016
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11.When a mixture of oil and water sits undistrubed, two distict layers will form. This is because
a) oil molecules are attracted to each other by LDF and water molecules are attracted to each other by hydrogen bonding, so the two substances separate
b) oil and water react to form a new substance that rises to the top
c) the less dense substance will rise to the top
d) Both A and C are true
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12. Which equation for dissolving a salt in water is written correctly?
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November 22, 2016
Jan 54:51 PM
13. Which solute would dissolve in carbon tetrachloride?
a) SrF2
b) CH3OH
c) CH2O
d) NaCl
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15. What is the sodium ion concentration when 70.0 mL of 3.0 M Na2CO3 is added to 30 mL of 1.0 M NaHCO3?
a) 0.45 M
b) 4.5 M
c) 2.4 M
d) 5.1 M
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Bonus FRQQuiz Tomorrow
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