Quick Review Classification of Matter Physical/Chemical Prop. Physical/Chemical Changes Intensive/Extensive Soluble vs Miscible.

Quick Review• Classification of Matter• Physical/Chemical Prop.

• Physical/Chemical Changes• Intensive/Extensive• Soluble vs Miscible

Slightly-less Quick Review

• Solution Terms and Types

A ____________ is a homogenous mixture of two or more substances

The ____________ is(are) the substance(s) present in the smaller amount(s)

The ____________ is the substance present in the larger amount

Types of Solutions

A solution is a homogenous mixture of two or more substances

The solute is(are) the substance(s) present in the smaller amount(s)

The solvent is the substance present in the larger amount

Types of Solutions

A ______________ ______________ contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.

An ______________ ______________ contains less solute than the solvent has the capacity to dissolve.

A ______________ ______________ contains more solute than is present in a saturated solution.

Sodium acetate crystals rapidly form when a seed crystal is added to a supersaturated solution of sodium acetate.

A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.

An unsaturated solution contains less solute than the solvent has the capacity to dissolve.

A supersaturated solution contains more solute than is present in a saturated solution.

Sodium acetate crystals rapidly form when a seed crystal is added to a supersaturated solution of sodium acetate.

Solution Math Review

Concentration Units Continued

M =moles of solute

liters of solution

Molarity

Molality

m =moles of solute

mass of solvent (kg)

Dilution: M1V1 = M2V2

S1

P1

= S2

P2

Henry’s Law:

Review• 1) Explain how you would prepare 500. mL of a 0.33 M

solution of sodium chloride.

• 2) Determine the molal concentration of a solution in which 320. grams of glucose C6H12O6 are dissolved in 4000 grams of water.

• 3) If the solubility of Carbon Dioxide in water is .625g/L at 790. Torr and 25.0 degrees Celsius; what would be the solubility at constant temperature and 3.00 atm?

• 4) If water and ethanol mix in all proportions they are said to be?

• If however water and oil don’t mix at any proportion they are said to be?

Solubility (The whole truth this time)

Full disclosure:While we do have PLENTY to cover….and I really hate adding more to it…The IB exams will not expect much from in terms of enthalpy of solution. I’m still going to cover it because I think it will be helpful background for upcoming material.

Also note the lack of colligative properties….

“Like dissolves like”

Two substances with similar intermolecular forces are likely to be soluble in each other.

• non-polar molecules are soluble in non-polar solvents

CCl4 in C6H6

• polar molecules are soluble in polar solvents

C2H5OH in H2O

• ionic compounds are more soluble in polar solvents

NaCl in H2O or NH3 (l)

• oil (non-polar) and water (polar) don’t mix

Enthalpy of Solution• Enthalpy is the sum of internal energy in a substance• However, commonly (and confusingly) it is most often used in terms

of enthalpy CHANGE (energy leaving or entering the substance in the form of heat.)

• Enthalpy of Solution refers to the overall amount of heat absorbed/released in the process of dissolving (exothermic/endothermic)

• MOST BEFUDDLING: – A substance getting cooler– A substance absorbing energy– An endothermic process

• Results in a POSITVE enthalpy change. (Because enthalpy is in terms of the substances energy)

Three types of interactions in the solution process:• solvent-solvent interaction• solute-solute interaction• solvent-solute interaction DHsoln = DH1 + DH2 + DH3

Solute molecules separate. This is an endothermic process because energy is required for this reaction, so ΔH1 > 0. (Positive)

Also needs to overcome the intermolecular forces holding it together. Like the first step, this reaction is an endothermic one and ΔH2 > 0 (Positive) because energy is required to break the forces between the molecules.

The separated solute molecules and the separated solvent molecules join together to form a solution. This is an exothermic reaction, because energy is given off as the two substances bond together; therefore, ΔH3 < 0. (Negative)

SOLUBILITYRule of thumb? Why? Explained by energies of solution formation.3 parts to solution formation:• Breaking up (expanding) the solute ∆H1

positive and higher for polar/ionic• Overcoming the intermolecular forces in (expanding) the solvent

∆H2 Also + and higher for polar/ionic• Solvent and solute interaction to form solution ∆H3 Negative

∆Hsoln = ∆H1 + ∆H2 + ∆H3

Enthalpy (heat) of solution Lattice Enthalpy(Of Solute H1 and Solvent H2

separation)

Heat of Solvation

IllustrationsOil in water; NaCl in water; I2 in hexane

Examples

1. If ΔHsolution = 230 J/mol, ΔH2 = 108 J/mol, and ΔH3 = - 47 J/mol, what is the value of ?H1?

ΔHsolution = ΔH1 + ΔH2 + ΔH3

230 J/mol = ΔH1 + 108 J/mol + - 47 J/mol

ΔH1 = 230 J/mol - 108 J/mol +47 J/mol

ΔH1 = 169 J/mol

2. If ΔHsolution = -219 J/mol, is the solution ideal or nonideal?

Solution is only ideal when ΔHsolution = 0

-219 J/mol does not equal 0

Therefore, the solution is non-ideal.

The dreaded ENERGY DIAGRAMThe following cycle is for calcium chloride, and includes a lattice dissociation enthalpy of +2258 kJ mol-1.

We have to use double the hydration enthalpy of the chloride ion because we are hydrating 2 moles of chloride ions.

So . . . ΔHsol = +2258 - 1650 + 2(-364)

ΔHsol = -120 kJ mol-1

Identify which in each pair would be most soluble in water:

hexane or ethanol Ethanol or octanol

↑ temperature generally increases solubility for solid in liquid

↑ pressure increases solubility of gas in liquid

When does solubility of a solid not increase with temp?

Summary

• So…To over simplify it: Solubility of a solute increases with increasing similarity to it’s solvent (In terms of IMF’s and THEN size.

• So basically Like-dissolves-like UNLESS the solute molecule is huge (and thus the London-Dispersion Forces require too much energy to break)

• NOTE: MOST “SOLID DISSOLVING” SOLUTION FORMATION IS ENDOTHERMIC +∆H

• What about “Gas dissolving solution formation?

Solution Math

Concentration UnitsThe concentration of a solution is the amount of solute present in a given quantity of solvent or solution.

Weight or Mass percent

% by mass = x 100%mass of solutemass of solute + mass of solvent

= x 100%mass of solutemass of solution

Mole Fraction

XA = moles of A

sum of moles of all components

SOLUTIONS

Solution Composition [concentration]

Mass % - mass solute x 100mass solution

Mole fraction of A = nA = χAnA + nB

Molality = mol solute kg solvent

Molarity = mol solute L solution

Normality = # equivalents L solution

For acid-base, 1 eq = mass of A or B which produces 1 mol of H+ or OH-.

For redox 1 eq = quantity of oxid or red agent which will provide or accept 1 mol of e-.

SOLUTIONS

What is the molality of a solution prepared by dissolving 18.3 g of cobalt(II) nitrate in 500. mL H2O? What is m for the ions?

How would you prepare 250. mL of a 2.00 M solution of NaOH?

What is the normality of a 0.500 M solution of HCl? H2SO4?

Colligative Properties• Adding a solute to a solvent affects the properties of the solvent.• Vapor pressure is depressed

– Raoult’s Law: PA = P0A x (nA/nsoln)

– Distillation

• Boiling Point is elevated• Freezing point is depressed• Osmotic Pressure is elevated

– Osmosis

*Osmosis is the spontaneous movement of solvent particles through a membrane towards a region of higher solute concentration. Tends to even out solute concentrations.*The osmotic pressure of a solution is the pressure difference needed to stop the flow of solvent across a semipermeable membrane

* Raoult's law states that the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperature scaled by the mole fraction of the solvent present:(Because Solute particles block solvent from evaporating to a vapor, the initial vapor pressure is reduced by a factor of the mole fraction.)

Raoult's law states that the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperature scaled by the mole fraction of the solvent present:

Or…Because Solute particles block solvent from evaporating to a vapor, the initial vapor pressure is reduced by a factor of the mole fraction.

Raoult’s Law: PA = P0A x (nA/nsoln)

Recall from Chem One:At any given temperature for a particular solid or liquid, there is a pressure at which the vapor formed above the substance is in dynamic equilibrium with its liquid or solid form. This is the vapor pressure of the substance at that temperature. At equilibrium, the rate at which the solid or liquid evaporates is equal to the rate that the gas is condensing back to its original form. All solids and liquids have a vapor pressure, and this pressure is constant regardless of how much of the substance is present.

Temperature and Solubility

Solid solubility and temperature

solubility increases with increasing temperature

Temperature and Solubility

Solid solubility and temperature

solubility decreases with increasing temperature

Fractional Crystalization is the separation of a mixture of substances into pure components on the basis of differing solubilities.

Suppose you have 90 g KNO3 contaminated with 10 g NaCl.

Fractional crystallization:

1. Dissolve sample in 100 mL of water at 600C

2. Cool solution to 00C

3. All NaCl will stay in solution (s = 34.2g/100g)

4. 78 g of PURE KNO3 will precipitate (s = 12 g/100g). 90 g – 12 g = 78 g

Temperature and Solubility

Gas solubility and temperature

solubility usually decreases with increasing temperature

Pressure and Solubility of Gases

The solubility of a gas in a liquid is proportional to the pressure of the gas over the solution (Henry’s law).

low P

low c

high P

high c

Fractional Distillation Apparatus

Vapor Pressure Depression• Vapor pressure is caused by solvent evaporation• Adding a non-volatile solute ALWAYS lowers the

vapor pressure– more solute = less solvent at surface = ↓ evaporation =

↓ vapor = ↓ vapor pressure

• Amount of solute is the only thing that alters this property – colligative property– 1 mol glucose 1 mol glucose– 1 mol NaCl 1 mol Na+ and 1 mol Cl-

– van’t hoff factor – mol of particles per mol of solute

DissociationKCl(aq) = K+ (aq) + Cl- (aq)

CuSO4(aq) = Cu+2(aq) + SO42-(aq)

K2SO4(aq) = 2 K+ (aq) + SO42-(aq)

K+ Cl-K Cl

Cu+2 SO42-Cu SO4

K+

SO42-

K+

KK SO4

Boiling Point Elevation

• For something to boil the vapor pressure = atmospheric pressure.

• Adding solute = ↓ vapor pressure = ↑ boiling point

• Example – adding salt to water before cooking spaghetti noodles causes that water to boil at a hotter temperature, which leads to the noodles cooking faster

Freezing Point Depression

• During freezing, the particles of a solid take on an orderly pattern.

• Adding solute disrupts this pattern, so even more energy must be removed for the solution to solidify.

• Examples – applying salt to icy roads helps prevent the water from freezing and the use of antifreeze in vehicles.

BPE and FPD Calculations

• BPE/FPD = kmi• k = a different constant for each solvent

= positive for BP (.512 kg0C/mol for H2O)

= negative for FP (-1.86 kg0C/mol)• m = molality• i = van’t hoff factor

Examples – Colligative Calculations

• What is the boiling point of a solution that contains 1.25 mol of CaCl2 in 1400. mL of H2O?

• What is the freezing point of 72.3 g of magnesium sulfate in 1350 mL of H2O

• The freezing point for H2O is lowered to -0.3900C when 3.90 g of a non-volatile molecular solid is dissolved in 475 g H2O. Calculate the molar mass of the substance.

Boiling-Point Elevation

Osmosis

Passive Transport is the selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated one.

A Semi-Permeable Membrane _____ allows the passage of solvent molecules but blocks the passage of solvent molecules.

__________________________ (p) is the pressure required to stop osmosis.

dilutemoreconcentrated

A cell in a/an:

_Hypotonic_SolutionLow Solute Conc.

Isotonic__solution

_Hypertonic__SolutionHigh Solute Conc.

A _Colloid__ is a dispersion of particles of one substance throughout a dispersing medium of another substance.

Colloid versus solution

• Particles: Solution < Colloid < Suspension

• collodial suspensions have many subtypes based on their medium’s state.

Types of Colloids

The Cleansing Action of Soap

Each soap molecule has a long hydrocarbon chain, sometimes called its 'tail', with a carboxylate 'head'. In water, the sodium or potassium ions float free, leaving a negatively-charged head.

• The organic part of a natural soap is a negatively-charged, polar molecule. Its hydrophilic (water-loving) carboxylate group (-CO2) interacts with water molecules via ion-dipole interactions and hydrogen bonding.

• The hydrophobic (water-fearing) part of a soap molecule, its long, nonpolar hydrocarbon chain, does not interact with water molecules. The hydrocarbon chains are attracted to each other by dispersion forces and cluster together, forming structures called micelles. In these micelles, the carboxylate groups form a negatively-charged spherical surface, with the hydrocarbon chains inside the sphere. Because they are negatively charged, soap micelles repel each other and remain dispersed in water.

Grease and oil are nonpolar and insoluble in water. When soap and soiling oils are mixed, the nonpolar hydrocarbon portion of the micelles break up the nonpolar oil molecules. A different type of micelle then forms, with nonpolar soiling molecules in the center. Thus, grease and oil and the 'dirt' attached to them are caught inside the micelle and can be rinsed away.

Chem. One Review

Review• 1) Explain how you would prepare 500. mL of a 0.33 M

solution of sodium chloride.

• 2) Determine the molal concentration of a solution in which 320. grams of glucose C6H12O6 are dissolved in 4000 grams of water.

• 3) If the solubility of Carbon Dioxide in water is .625g/L at 790. Torr and 25.0 degrees Celsius; what would be the solubility at constant temperature and 3.00 atm?

• 4) If water and ethanol mix in all proportions they are said to be?

• If however water and oil don’t mix at any proportion they are said to be?

Colligative Properties• Depend only on the number of

solute particles present, not on the identity of the solute particles.

• Among colligative properties areVapor pressure depression Boiling point elevationFreezing point depressionotic pressure

Heterogeneous Aqueous Systems

• Two types:1. Suspension

- a mixture from which particles settle out- suspension differs from a solution because the particles of a suspension are much larger & do not stay suspended (> 1000 nm)- Ex. – muddy water, gravy

2. Colloid- a mixture containing intermediate-sized particles larger than those in solutions but smaller than those in a suspension (1-1000 nm)- Ex. – glue, paint, smoke, milk, fog

Colloid ClassificationMedium / Phases

Dispersed phase

Gas Liquid Solid

Continuous medium

GasNONE(All gases are mutually miscible)

Liquid aerosolExamples: fog, mist, hair sprays

Solid aerosolExamples: smoke, cloud, air particulates

LiquidFoamExample: whipped cream, Shaving cream

EmulsionExamples: milk, mayonnaise, hand cream

SolExamples: pigmented ink, blood

Solid

Solid foamExamples: aerogel, styrofoam, pumice

GelExamples: agar, gelatin, jelly

Solid solExample: cranberry glass

Comparison of Particle Size

• Solution– Less than 1 nm

• Colloid– Between 1 nm and 1000 nm

• Suspension – Larger than 1000 nm

Tyndall Effect

• The scattering of visible light by colloidal particles is called the Tyndall effect.

• Good test to distinguish between a solution and a colloid.