CHEMISTRY II

UNIVERSIDAD AUTÓNOMA DE NUEVO LEON

CIDEB

STAGE II: AQUEOUS

SOLUTIONS

STAGE 2: AQUEOUS SOLUTIONS

Formative Objective: The student identifies common solutions in the surrounding, distinguishes their composition by calculations of concentration using theoretical and experimental data, and recognizes drinking water as a vital dissolution.

ANTIFREEZE SEA WATER STEEL

AIR SOFT DRINKS ITALIAN DRESSING

FOG SPRAY DEODORANT

MUDDY WATER

IRON FILINGS AND SULFUR

SHAVING FOAM

STRAWBERRYJELLY

DENTAL AMALGAM

MAYONNAISE BLOOD

COPPER WIRE

CARBONDIOXIDE

DISTILLED WATER

1

14

11

13

10

7

4

8

5

2 3

6

9

12

15

18

16 17

TYPES OF HETEROGENEOUS MIXTURES

Suspensions

• Mixture containing particles that settle out if left undisturbed.

• Pouring a liquid suspension through a filter will separate out the suspended particles.

• Particles in a suspension are much larger than atoms and can settle out of solution

Colloids

• Heterogeneous mixture of intermediate-sized particles (between 1 and 1000 nm in diameter.

• Particles do not settle out.

• The dispersed particles make random movements called Brownian motion.

• Present Tyndall effect.

HOMOGENEOUS MIXTURES: SOLUTIONS

Homogeneous mixtures that contain two or more substances called the solute and the solvent. Atoms Ions Molecules

SOLUTE: the substance being dissolved (the substance with the lesser amount)

SOLVENT: the dissolving medium; the component whose physical state is retained (the substance present in the greater amount).

TYPES OF SOLUTIONS

FORMING SOLUTIONS

Soluble: A substance that dissolves in a solvent; (sugar in water)

Insoluble: A substance that does not dissolve in a solvent (sand in water).

Miscible: Two liquids that are soluble in each other in any proportion, (such as the antifreeze)

Immiscible Two liquids that can be mixed together but separate shortly after (Oil and vinegar

PROPERTIES OF TRUE SOLUTIONS The particles of solute are the size of molecules or ions. The mixture does not separate on standing. The mixture does not separate by common fiber filter. The

entire solution will pass through the filter. Once it is completely mixed, the mixture is homogeneous.

If you take a sample of the solution from any point in the solution, the proportions of the materials will be the same.

The mixture appears clear rather than cloudy. It may have some color to it, but it seems to be transparent otherwise. The mixture shows no Tyndall effect.

The solution of ionic materials into water will result in an electrolyte solution.

The solution shows an increase in boiling point as the amount of solute is increased.

SOLUBILITY AND SOLVATION PROCESS

THINK ABOUT IT...

Why salt is soluble in water and oil is not?

While preparing lemonade it is the same to: Use Cold water / room temperature water Use Sugar in cubes / granulated sugar Stirring the mix / Not stirring

WHY?

?

THE SOLVATION PROCESS

The process of surronding solute particles with solvent particles to form a solution is called SOLVATION.

If solvation occurs in water is called Hydration.

“Like dissolves like”

http://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0078807239/602901/Dissolution_of_Cmpds_fig_13_15.swf::Dissolution of compounds

SOLUBILITY

Water molecules surrond the ions of the solute: Hydration.

Each ion becomes completely separated from the solid crystal and become hydrated.

Water solubility depends on the formation of hydrogen bonds.

Molecules containing a high proportion of nitrogen or oxygen atoms usually dissolve in water because the formation of hydrogen bonds

Ionic CompoundsCovalent Compounds

FACTORS THAT AFFECT SOLVATION

• Stirring allows new collisions between solute and solvent particles

• Stirring increases the speed of dissolving

Agitation

• Breaking solute into small pieces increases its surface area;

• The greater the surface area is, the quicker it will dissolve

Surface area

• For solids; solubility increases with temperature.

• For gases; solubility decreases with temperature

Temperature

SOLUBILITY OF GASES

• Gases are less soluble at higher temperatures than at lower temperatures.

• As a solution’s temperature increases, the solubility of a gaseous solute decreases.

Temperature

• The solubility of a gas in any solvent increases as its external pressure (the pressure above the solution) increases.

Pressure

1. Process of surronding solute particles with solvent particles to form a solution.

2. Kind of compounds where solvation occurs when water molecules surround ions.

3. Kind of compound where solvation occurs forming hydrogen bonds.

4. Overall energy change during the solution formation

5. Factors that affect solvation (3)

REVIEW

SOLUBILITY: MEASURE OF HOW MUCH OF THE SOLUTE CAN BE DISSOLVED INTO THE SOLVENT.

• Contains less dissolved solute for a given temperature and pressure than a saturated solution; more solute can be dissolved in an unsaturated solution.

Unsaturated solutions

• Contains the maximum amount of dissolved solute for a given amount of solvent at a specific temperature and pressure.

Saturated solutions

• Contains more dissolved solute than a saturated solution at the same temperature. • To make a supersaturated solution, a saturated solution is formed at a high temperature and then cooled slowly. The slow cooling allows the excess solute to remain dissolved in solution at the lower temperature

• Are unstable. If a tiny amount of solute, called a seed crystal, is added to a supersaturated solution, the excess solute precipitates quickly,

Supersaturated solution:

SOLUBILITY GRAPH

Determine the solubility of KClO3 at 70º C

Determine if the solution of 50g of NaCl in 100g of water at 80ºC is unsaturate, saturate or supersaturate.

SOLUTION CONCENTRATION

A measure of how much solute is dissolved in a specific amount of solvent or solution.

• Concentrated : contains a large amount of solute.

• Dilute: contains a small amount of solute.

Qualitative:

• Percent by mass• Percent by volume• Molarity

Quantitative:

QUANTITATIVE DESCRIPTIONS

These descriptions express concentration as a ratio of measured amounts of solute and solvent or solution.

PERCENT BY MASS Is the ratio of the solute’s mass to the

solution’s mass expressed as a percent. The mass of the solution equals the sum of

the masses of the solute and the solvent.

PERCENT BY VOLUME Usually describes solutions in which both

solute and solvent are liquids; is the ratio of the volume of the solute to the volume of the solution, expressed as a percent.

The volume of the solution is the sum of the volumes of the solute and the solvent.

% MASS-VOLUME

Calculate the percent by mass/volume of a prepared solution dissolving 30g of ethanol in water to fill up 100ml with distilled water.

grams of solute%m/m = x100

volume of solution

MOLARITY Is the number of moles of solute dissolved

per liter of solution. Molarity is also known as molar concentration, and the unit M is read as molar. A liter of solution containing 1 mol of solute is a

1M solution

DILUTING MOLAR SOLUTIONS