Advchem2
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Transcript of Advchem2
SOLUTIONS
DEFINITION
• a mixture where the components are uniformly intermingled
• a mixture that is homogeneous
TYPES
• Gaseous solution
• Liquid solution
• Solid solution
RecallSolute• what is dissolved in a solution
Mass• a measure of the amount of matter in
an object (g or kg)
Volume• measures the size of an object using length
measurements in three dimensions (ml or L)
RecallMole (mol)
• also known as Avogadro's Number• number that is used in making calculations
involving atoms and molecules• 1 mol is equal to 6.022 x 1023 atoms or molecules• Molar Mass (MM) of elements and compounds is
the mass, in grams, equal to the atomic and formula masses of those elements and compounds. The unit of Molar Mass is grams/mole
Practice
Calculate the molar mass of the following:
• CO2 = 44.01 grams/mole
• H2O = 18.02 grams/mole
• NaCl = 58.44 grams/mole
CONCENTRATION
Relative Amounts of Solute and Solvent
in a Solution
Ways to Express the Relative Amounts of Solute and Solvent in a Solution
• Percent concentration (by mass; by volume)
• Molarity (M)
• Molality (m)
• Mole fraction (X)
● Percent Composition (by mass; by volume)
We need two pieces of information to calculate the percent by mass of a solute in a solution:
• mass/volume of the solute in the solution
• mass/volume of the solution
By mass:
• % (w/w) =
By volume:
• % (v/v) =
100xsolutionmasssolutemass
100xsolutionvolumesolutevolume
● Percent Composition (by mass; by volume)
Practice
• 10 g salt and 70 g water are mixed to make a solution. Find the concentration of the solution by percent mass.
12.5 %
Practice
• The concentration by volume of a 1.5 L NaCl solution is 40 %. Find the amount of solute in this solution.
0.6 L
● Molarity (M)
Molarity tells us the number of moles of solute in exactly one liter of a solution.
We need two pieces of information to calculate the molarity of a solute in a solution:
• moles of solute present in the solutio
• volume of solution (in liters) containing the solute
● Molarity (M)
Practice
• What is the molarity of a solution that contains 1.724 moles of H2SO4 in 2.50 L of solution?
0.690 M H2SO4
Practice
• What is the molarity of a solution prepared by dissolving 25.0 g of HCl (g) in enough water to make 150.0 mL of solution?
4.57 M HCl
● Molality (m)
Molality, m, tells us the number of moles of solute dissolved in exactly one kilogram of solvent.
We need two pieces of information to calculate the molality of a solute in a solution:
• moles of solute present in the solution
• mass of solvent (in kilograms) in the solution
● Molality (m)
Recall: density of water = 1.00 g / mL or 1 kg/L
Practice
• Suppose you had 58.44 grams of NaCl and you dissolved it in exactly 2.00 kg of pure water. What would be the molality of the solution?
0.5 m
Practice
• 80.0 grams of glucose (C6H12O6, mol. wt = 180 g/mol) is dissolved in 1.00 L of water. What is its molality?
0.44 m
● Mole Fraction (X)
The mole fraction, X, of a component in a solution is the ratio of the number of moles of that component to the total number of moles of all components in the solution.
To calculate mole fraction, we need to know:• number of moles of each component present
in the solution
● Mole Fraction (X)
NOTE:
The sum of the mole fractions for each component in a solution will be equal to 1
Practice
• A solution is prepared by mixing 25.0 g of water, H2O, and 25.0 g of ethanol, C2H5OH. Determine the mole fractions of each substance.
XH2O = 0.71
XC2H5OH = 0.29
COLLOIDS
• a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium
DEFINITION
• the size of the dispersed molecule is larger than a simple molecule (having diameter between 1 to 1000 nm) but small enough to remain suspended
• an intermediate state between suspensions and solutions
THE TYNDALL EFFECT
• colloidal suspensions exhibit light scattering• named after its discoverer, the 19th-century
British physicist John Tyndall• a special instance of diffraction (bending of
light)• often used as a measure of the existence of a
colloid• visible in colloids as weak as 0.1 ppm
(exception?)
TYPES AND EXAMPLES
based on physical state of dispersion medium and dispersed phase
medium: SOLIDphase: SOLID Solid Sols
Gemstones
Pearls
Some coloured glass
medium: SOLIDphase: GAS Solid Sols
Pumice Foam Rubber
medium: SOLIDphase: LIQUID Gels
Cheese Shoe polish Butter
Jellies Jam
medium: LIQUIDphase: LIQUID Emulsion
Milk Hair Cream
Cod liver oil
medium: LIQUIDphase: GAS Foam
Froth
Soap latherWhipped cream
medium: LIQUIDphase: SOLID Sols
Paints
Gum
Muddy water
medium: GASphase: LIQUID Aerosol
Fog
Clouds Insecticide spray
medium: GADphase: SOLID Aerosol
Smoke Dust
medium: GASphase: GAS
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At a glance
MEDIUM \ PHASE SOLID LIQUID GAS
SOLID Solis Solsgemstones, pearls, some coloured glass
Gelscheese, butter, shoe polish, jellies, jam
Solid Solspumice, foam rubber
LIQUID Solsgum, paint, muddy water
Emulsionmilk, hair cream, cod liver oil
Foamfroth, whipped cream, soap lather
GAS Aerosolsmoke, dust
Aerosolclouds, spray, fog
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