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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