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SOLUTIONS AND SOLVATION. The Straight and Narrow Path to Solution. The Day of Judgement. For You will be tested on 21 February It is coming, You must be prepared. You must know your solutions You must know your Molarity You must know your way to solve the problems. MIXTURES VS COMPOUNDS. - PowerPoint PPT Presentation
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SOLUTIONS AND SOLUTIONS AND SOLVATIONSOLVATION
SOLUTIONS AND SOLUTIONS AND SOLVATIONSOLVATION
The Straight and Narrow Path to The Straight and Narrow Path to SolutionSolution
The Day of Judgement• For You will be tested on 21
February• It is coming, You must be prepared.• You must know your solutions• You must know your Molarity• You must know your way to solve
the problems
MIXTURES VS COMPOUNDS
• Compounds: Chemically combined substances.
• Mixtures: Physically combined substances, normally made up of two or more compounds.
• Heterogeneous: Different Concentrations everywhere. It isn’t the same.
• Homogeneous: Exactly the same concentrations everywhere. It’s all the same everywhere.
SOLVATION• The process of dissolving a solute in a solvent• Solutes: The material that is present in
smaller amounts • Solvents: The material that is present in the
largest amount, can only be one in a solution• And the Solvent said unto the Solute, “Come
and be Dissolved by me!”NaCl(s) Na+(aq) + Cl-(aq)
What can be Solvated• Soluble: The material can be dissolved.• Insoluble: The material can’t be dissolved• Miscible: A liquid that will dissolve• Immiscible: A liquid that will not dissolve• Solubility: How much can dissolve under
the given conditions• Alloy: A metal that is dissolved in
another metal.
Polar in Polar• And the Like Molecules shall be
dissolved by the Like Molecules, Polar unto Polar and Nonpolar unto Nonpolar each Unto it’s own kind
• Unlike Molecules shall not be dissolved by Unlike Molecules, Polar SHALL NOT dissolve Nonpolar, Oil and Water Shall Not dissolve.
Common Polar Solvents• Water: H2O
• Ammonia: NH3
• Ethanol: CH3OH
Water is Polar• As you can see, water has a
positive side and a negative side.
The Process• NaCl goes down into the Water
The Water surrounds the NaCl pulling it apart, Na to the Negative side of water and Cl to the positive side of water and the NaCl is no more, it has been dissolved – it is one with the water. Polar unto Polar.
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf
NonPolar in NonPolar• The NonPolar molecules become
surrounded by the NonPolar Molecules, LIKE UNTO LIKE, surrounded the Nonpolar Solute is carried away as one with the Nonpolar Solvent.
Common Nonpolar Solvents
• Fats• Oil• Gasoline• Covalent Compounds
Electrolytes versus Nonelectrolytes
• Electrolytes completely break apart and carry an electrical current. Polar
• Nonelectrolytes don’t break apart and don’t carry an electrical current. NonPolar
Like Dissolves Like• Polar substances are dissolved by
Polar Substances• Nonpolar substances are dissolved
by Nonpolar Substances.• Polar does not dissolve Nonpolar.• Nonpolar does not dissolve polar.
Nonpolar will not dissolve in Polar
• Iodine is NonPolar, water is Polar, so it won’t dissolve
• Iodine will dissolve in Carbon Tetra Chloride which is NonPolar.
TYPES OF SOLUTIONS• UNSATURATED: The solution can
dissolve more solute.• SATURATED: The solution cannot
dissolve more solute.• SUPERSATURATED: The solution
has dissolved more solute then it should.
UNSATURATED• More can be added
SATURATED• The Solution cannot dissolve more:
SUPERSATURATED• The solution is holding more then it
should.• When more is added, a lot flows out.
What a Supersaturated Looks Like
• http://www.amazingrust.com/experiments/how_to/Hot-Ice.html
• http://www.wonderhowto.com/how-to-make-sodium-acetate-hot-ice-w-vinegar-baking-soda-274006/
SupersaturatedSupersaturatedSodium Sodium
AcetateAcetate• One application One application of a of a supersaturated supersaturated solution is the solution is the sodium acetate sodium acetate “heat pack“heat pack.”.”
SUPERSATURATED• HOW IT HAPPENS• As a general rule: Solvents can hold a certain
amount of Solute at a certain temperature• If the temperature is raised, more solute can
be dissolved.• If the solution is then cooled, the solute stays
dissolved.• The solution is holding more solute then it
should.
How solutions are measured
• Concentration: How much solute there is in a given amount of Solvent.
• Molarity: Moles solute/Liters solution• Molality: Moles solute/Kilograms
solvent• Mass Percent: grams solute/grams
solution
Concentration of Concentration of SoluteSolute
Concentration of Concentration of SoluteSolute
The amount of solute in a The amount of solute in a solution is given by its solution is given by its concentrationconcentration.
Molarity (M) = moles soluteliters of solution
Properties of solutions• Colligative property: A property
that changes as a result of the solution being made
• Vapor Pressure Lowering: The vapor pressure of the solution goes down, the amount of substance release into the air goes down.
More properties of solutions
• Boiling Point elevation: Boiling point of a solution is higher then that of just the solvent.
• Freezing Point depression: Freezing point of a solution is lower then that of just the solvent.
• Electrolyte: A substance in a solution that allows the solution to transmit an electric current
Some DefinitionsSome DefinitionsA solution is a mixture A solution is a mixture
of 2 or more of 2 or more substances in a substances in a single phase. single phase.
One constituent is One constituent is usually regarded as usually regarded as the the SOLVENTSOLVENT and and the others as the others as SOLUTESSOLUTES..
Parts of a Solution• SOLUTE – the part
of a solution that is being dissolved (usually the lesser amount)
• SOLVENT – the part of a solution that dissolves the solute (usually the greater amount)
• Solute + Solvent = Solution
Solute
Solvent
Example
solid
solid Brass
solid
liquid
Tea, Coffee
gas solid Foamliquid
liquid
Ammonia
gas liquid
Carbonated Water
gas gas Air
IONIC COMPOUNDSIONIC COMPOUNDSCompounds in Aqueous SolutionCompounds in Aqueous Solution
Many reactions involve ionic Many reactions involve ionic compounds, especially reactions in compounds, especially reactions in water — water — aqueous solutions.aqueous solutions.
KMnOKMnO44 in water in water KK++(aq) + MnO(aq) + MnO44--(aq)(aq)
How do we know ions are How do we know ions are present in aqueous present in aqueous solutions?solutions?
The solutions conduct The solutions conduct electricityelectricity
They are called They are called ELECTROLYTESELECTROLYTES
HCl, MgClHCl, MgCl22, and NaCl are , and NaCl are strong electrolytes. strong electrolytes. They They dissociate completely (or dissociate completely (or nearly so) into ions.nearly so) into ions.
Aqueous SolutionsAqueous Solutions
Aqueous Aqueous SolutionsSolutions
Some compounds Some compounds dissolve in water but dissolve in water but do not conduct do not conduct electricity. They are electricity. They are called called nonelectrolytes.nonelectrolytes.
Examples include:Examples include:sugarsugarethanolethanolethylene glycolethylene glycol
Examples include:Examples include:sugarsugarethanolethanolethylene glycolethylene glycol
PROBLEM: Dissolve 5.00 g of NiClPROBLEM: Dissolve 5.00 g of NiCl22•6 •6 HH22O in enough water to make 250 O in enough water to make 250 mL of solution. Calculate the mL of solution. Calculate the Molarity.Molarity.
PROBLEM: Dissolve 5.00 g of NiClPROBLEM: Dissolve 5.00 g of NiCl22•6 •6 HH22O in enough water to make 250 O in enough water to make 250 mL of solution. Calculate the mL of solution. Calculate the Molarity.Molarity.
Step 1: Step 1: Calculate moles Calculate moles of NiClof NiCl22•6H•6H22OO
5.00 g • 1 mol
237.7 g = 0.0210 mol
0.0210 mol0.250 L
= 0.0841 M
Step 2: Step 2: Calculate MolarityCalculate Molarity
[NiClNiCl22•6 H•6 H22OO ] = 0.0841 M
Step 1: Step 1: Change mL to L.Change mL to L.
250 mL * 1L/1000mL = 0.250 L250 mL * 1L/1000mL = 0.250 L
Step 2: Step 2: Calculate.Calculate.
Moles = (0.0500 mol/L) (0.250 L) = 0.0125 molesMoles = (0.0500 mol/L) (0.250 L) = 0.0125 moles
Step 3: Step 3: Convert moles to grams.Convert moles to grams.
(0.0125 mol)(90.00 g/mol) = (0.0125 mol)(90.00 g/mol) = 1.13 g1.13 g
USING MOLARITYUSING MOLARITYUSING MOLARITYUSING MOLARITY
moles = M•Vmoles = M•V
What mass of oxalic acid, What mass of oxalic acid, HH22CC22OO44, is, is
required to make 250. mL of a 0.0500 Mrequired to make 250. mL of a 0.0500 Msolution?solution?
Learning Check
How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution?
1) 12 g2) 48 g3) 300 g
Two Other Concentration Two Other Concentration UnitsUnits
grams solutegrams solutegrams solutiongrams solution
MOLALITY, mMOLALITY, m
% by mass% by mass = =
% by mass% by mass
m of solution = mol solute
kilograms solvent
Calculating Calculating ConcentrationsConcentrations
Calculate molalityCalculate molality
Calculate molalityCalculate molality
Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g
of Hof H22O. Calculate m & % of ethylene glycol (by mass).O. Calculate m & % of ethylene glycol (by mass).
Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g
of Hof H22O. Calculate m & % of ethylene glycol (by mass).O. Calculate m & % of ethylene glycol (by mass).
conc (molality) = 1.00 mol glycol0.250 kg H2O
4.00 molalconc (molality) = 1.00 mol glycol0.250 kg H2O
4.00 molal
%glycol = 62.1 g
62.1 g + 250. g x 100% = 19.9%%glycol =
62.1 g62.1 g + 250. g
x 100% = 19.9%
Calculate weight %Calculate weight %
Learning Check
A solution contains 15 g Na2CO3 and
235 g of H2O? What is the mass %
of the solution? 1) 15% Na2CO3
2) 6.4% Na2CO3
3) 6.0% Na2CO3
Dilutions• Stock Solution: A solution of
known concentration, normally saturated, used to make other solutions.
• Diluting: Adding solvent to make a reduce the concentration of a solution.
Dilution Equation• M1V1 = M2V2
• Mr Simms needs 250 mL of 0.150 M CuCl2 Solution. He has 3.00 M Stock Solution. How much of the stock solution does he need to use?
Problem Set up• M1V1 = M2V2
• M1 = 0.150 M
• V1 = 250 mL
• M2 = 3.00 M
• V2 = X mL
Answer• (0.150 M)(250 mL) = (3.00 M)X• (0.150 M)(250 mL) = X• (3.00 M)• X = 12.5 mL• Explanation: I need to start with 12.5
mL of 3.00M Stock Solution and dilute it to 250 mL by adding 237.5 mL of Water.
Boiling Point Elevation T = (# ions)(molality)Kb
T = Change in Temperature, not new Temperature
• (# ions) = Number of ions, NaCl has 2, MgCl2 = 3, All Covalent compounds are 1.
• Molality = You should know this already
• Kb = a Boiling point constant for the Solvent
Example• What is the new boiling point for a
1.20 molal solution of NaI?T = (# ions)(molality)Kb
• # ions = 2• Molality = 1.20 molal
• Kb for water = 0.512 C/m
Example continuedT = (# ions)(molality)Kb
T = (2)(1.20)(0.512)T = 1.23 C
• Old Boiling point = 100
• New Boiling point = 101.23
Freezing Point Depression
• What would the new Freezing point of the solution be?
T = (# ions)(molality)Kf
• Kf for water is 1.86 C/m T = (2 ions)(1.2 m)(1.86 C/m) T = 4.46 C• Old Freezing point of water = 0• New Freezing point of water = 0 – 4.46 = -4.46 C