SolutionsChemistry

Mrs. Nunez

Solution - homogeneous mixture

Solvent - present in greater amount

Solute - substance being dissolved

Solvation the process of dissolving

solute particles are separated and pulled into solution

solute particles are surrounded by solvent particles

StrongElectrolyte

Non-Electrolyte

solute exists asions only

- +

salt

- +

sugar

solute exists asmolecules only

- +

acetic acid

WeakElectrolyte

solute exists asions andmolecules DISSOCIATION IONIZATION

Dissociationseparation of an ionic solid into aqueous ions

NaCl(s) Na+(aq) + Cl–(aq)

Ionization breaking apart of some polar molecules into aqueous ions

HNO3(aq) + H2O(l) H3O+(aq) + NO3–(aq)

Molecular Solvation

molecules stay intact

C6H12O6(s) C6H12O6(aq)

NONPOLAR

NONPOLARPOLARPOLAR

“Like Dissolves Like”

C. Johannesson

Soap/Detergentpolar “head” with long nonpolar “tail”dissolves nonpolar grease in polar water

SolubilitySATURATED SOLUTIONno more solute dissolves

UNSATURATED SOLUTIONmore solute dissolves

SUPERSATURATED SOLUTIONbecomes unstable, crystals form

concentration

Solubilitymaximum grams of solute that will

dissolve in 100 g of solvent at a given temperaturevaries with tempbased on a saturated soln

Factors determining rate of solution...1. stirring (agitation)2. surface area the dissolving particles3. temperature

C. Johannesson

C. SolubilitySolids are more soluble at...

high temperatures.

Gases are more soluble at...• low temperatures &• high pressures

(Henry’s Law).• EX: nitrogen narcosis,

the “bends,” soda

SolubilitySolubility Curveshows the dependence of solubility on temperature

Solids tend to dissolve best when:•They are heated

•They are stirred•Crushed into smaller particles

Gases tend to dissolve best when:

•The solution is cold•The pressure is high

LiquidsMiscible means that two liquids can dissolve in each otherwater and antifreezewater and ethanol

Partially miscible- slightlywater and ether

Immiscible means they can’toil and vinegar

Gases in liquids...Henry’s Law - says the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquidthink of a bottle of soda pop, removing the lid releases pressure

Equation: S1 S2 P1 P2

Sample 16.1, page 477

=

ConcentrationThe amount of solute in a solution.Describing Concentration

% by mass - medicated creams% by volume - rubbing alcoholppm, ppb - water contaminantsmolarity - used by chemistsmolality - used by chemists

Concentrated vs. Dilute

Lots of solute, in a

small amount of solvent.

Small amount of solute in a

large amount of solvent.

Notice how dark

the solutions appears.

Notice how

light the solution appears.

CONCENTRATED

DILUTE

A. MolarityConcentration of a solution.

solution of literssolute of moles(M)Molarity

total combined volume

substance being dissolved

Molarity

2M HCl

LmolM

L 1HCl mol 2HCl 2M

What does this mean?

Molarity CalculationsFind the molarity of a 250 mL solution containing 10.0 g of NaF. 10.0 g 1 mol

41.99 g = 0.238 mol NaF

0.238 mol0.25 L

M = = 0.95M NaF

LmolM

B. Molality

solvent ofkg solute of moles(m)molality

mass of solvent only

1 kg water = 1 L waterkg 1mol0.25 0.25m

MolalityFind the molality of a solution containing

75 g of MgCl2 in 250 mL of water.

75 g MgCl2 1 mol MgCl2

95.21 g MgCl2

= 3.2m MgCl2

0.25 kg water

kgmolm

2211 VMVM

C. DilutionPreparation of a desired solution by adding water to a concentrate.

Moles of solute remain the same.

DilutionWhat volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution?

GIVEN:M1 = 15.8MV1 = ?M2 = 6.0MV2 = 250 mL

WORK:M1 V1 = M2 V2

(15.8M) V1 = (6.0M)(250mL)

V1 = 95 mL of 15.8M HNO3

Preparing Solutions500 mL of 1.54M

NaCl

500 mLwater

45.0 gNaCl

• mass 45.0 g of NaCl• add water until total

volume is 500 mL• mass 45.0 g of NaCl• add 0.500 kg of water

500 mLmark

500 mLvolumetricflask

1.54m NaCl in 0.500 kg of water

Preparing Solutions250 mL of 6.0M HNO3

by dilutionmeasure 95 mL

of 15.8M HNO3

95 mL of15.8M HNO3

water for safety

250 mL mark

• combine with water until total volume is 250 mL

• Safety: “Do as you oughtta, add the acid to the watta!”

Percent solutions can be expressed by a) volume or b) mass

Percent means parts per 100, so

Percent by volume: = Volume of solute

x 100% Volume of solution

indicated %(v/v)Sample Problem 16.5, page 485

Percent solutions

Another way to do mass percentage is as mass/mass:

Percent by mass: = Mass of solute(g)

x 100% Mass of solution (g)

Indicated %(m/m)

property that depends on the concentration of solute particles, not their identity

Colligative Property

TypesFreezing Point Depression (tf)

f.p. of a solution is lower than f.p. of the pure solvent

Boiling Point Elevation (tb)

b.p. of a solution is higher than b.p. of the pure solvent

Vapor pressure lowering

- Page 488

Glucose will only have one particle in solution for each one particle it starts with.

NaCl will have two particles in solution for each one particle it starts with.

CaCl2 will have three particles in solution for each one particle it starts with.

Colligative Properties

Some particles in solution will IONIZE (or split), while others may not.

Freezing Point Depression

Solute particles weaken IMF in the solvent.

Boiling Point Elevation

- Page 494The addition of a solute would allow a LONGER temperature range, since freezing point is lowered and boiling point is elevated.

Applicationssalting icy roadsmaking ice creamantifreeze

cars (-64°C to 136°C)