5.) SOLUBILITY, POLARITY, ELECTROLYTES, AND NONELECTROLYTES

PURPOSE

Compare the SOLUBILITIES of SOME POLAR AND NONPOLAR SPECIES. Observe the SOLUBILITY OF IONIC OMPOUNDS IN WATER. Determine whcih are SEVERAL SPECIES CAN BE CLASSIFIED AS STRONGM WEAK, OR NONELECTROLYTES.

Physical propeties of substances is their SOLUBILITY

Ability to DISSOLVE IN A VARIETY OF SOLVENTS.

Water is an EXCELLENT SOLVENT with the ABILITY OT DISSOLVE A VARIETY OF CHEMICAL COMPOUNDS.

Water has a HIGHLY POLAR NATURE. The ELECTRONS IN A WATER MOLECULE are not DISTRIBUTED EQUALLY ABOUT THE MOLECULE. MORE CONCENTRATED near the OXYGEN ATOM adn less CONCENTRATED NEAR THE HYDROGEN ATOMS. Due to the difference of electronegativity values of Oxygen and Hydrogen. Water is ALSO A BEANT MOLECULE.

Water can DISSOLVE MANY IONIC AND POLAR COVALENT COMPOUNDS.

Like DISSOLVES LIKE. Polar compounds tend ot be soluble in polar solvents, and nonpolar compounds tend to be SOLUBLE IN NONPOLAR SOLVENTS.

Potassium Chloride dissolve in water, the CRYSTALLINE LATTICE IS DESTROYED AND K+ and Cl- ions are separated from each other.

The NEGATIVE END OF WATER i s attracted to K_ ions and the POSTIVE END OF WATER is attracted to Cl- ions.

HYDRATION

The process in whcih an ION IS SURROUNDED BY WATER MOLECULES.

This is an ENERGY RELEASING PROCESS. Hydration ENERGY overcomes the ELECTROSTATIC ATTRACTION between K+ and Cl- ions.

...

IONIC COMPOUNDS THAT HAVE STRONG IONIC BONDS do NOT dissolve in WATER because WATER MOECULES CANNOT PROVIDE SUFFICIENT HYDRATION ENERGY to separate the ions.

Bond strengths of IONIC COMPOUNDS ARE RELATED TO THE CHARGES AND SIZES OF THE IONS.

LATTICE ENERGY INCREASES with the INCREASING CHARGEs and DECREASING size of the ions.

This trend is reflected in the SOLUBILITY RULES FOR IONIC COMPUNDS IN WATER.

Fe(OH)3 is INSOLUBLE IN WATER. NaOH IS SOLUBLE IN WATER.

The hydration energy SUPPLIED BY WATER IS INSUFFICIENT TO DISRUPT HTE LARGE Fe(OH)3 crystal lattice and dissolve the compound.

For a MOLECULAR COVALENT COMPOUND TO BE POLAR THERE ARE TWO POINTS.

#NAME?

FOR A COVALENT BOND TO BE POLAR...

The difference in the electronegativity values of hte TWO ATOMS IN THE BOND MUST BE 0.4 OR HIGHER.

METHANE, bonds are IDENTICAL and hte MOLECULE IS SYMMETRICAL. IT is a NONPOLAR MOLECULE.

...

The SOLUBILITY OF A POLAR COMPOUND IN WATER is enhanced if the COMPOUND CAN HYDROGEN BOND WITH WATER.

Contains an O-H , N-H, or F-H bond.

METHANOL can HYDROGEN BOND WITH WATER. the OH group is highly polar .

...

When one liquid dissolves in another the liquids are MISCIBLE.

...

1-HEXANOL is INSOLUBLE IN WATER. CARBON ATOMS decrease the POLARITY OF THE OH GROUP.

...

THE MORE OH GROUPS, the more solubile a moeclule is with water.

...

NONPOLAR COMPOUNDS DISSOLVE IN NONPOLAR SOLVENTS BECAUSE THEY have INTERMOLECULAR forces. These are called DISPERSION FORCES OR LOND FORCES. T

The attraction of THE POSITIVE NUCLEUS OF ONE MOLECULE for the electron cloud in a nearby molecule. INDUCING A TEMPORARY DIPOLE ON THE NEIGHBORING MOLECULE.

Dispersion forces

Two molecules must be very close to one another for them to POLARIZE ONE ANOTHER. Dispersion forces increase with INCREASING MOLECULAR WEIGHT because the molecules contain LARGER NUMBERS OF ELECTRONS.

ELECTROLYTE

A substance that CONDUCTS ELECTRICITY WHEN DISSOLVED in water.

NONELECTROLYTE

A substance that DOES NOT CONDUCT ELECTRICTY WHEN DISSOLVE IN WATER.

STRONG ELECTROLYTES

Compounds that produce LARGE QUANTITIES OF IONS IN SOLUTION (strong acids, strong bases, and water soluble salts) CONDUCT ELECTRICITY WELL.

WEAK Electrolytes

COMPOUNDS that PRODUCE SMALL numbers of ions and exist as molecules in a solution (WEAK ACIDS AND BASES) are POOR CONDUCTORS OF ELECTRICTY.

A conductivity detector

Device used to DISTINGUISH BETWEEN ELECTROLYTES and NONELECTROLYTES. A piar of electrodes connected to a source of ELECTRIC CURRENT AND A LIGHT SOURCE. (LED light emitting diode) is immersed in a solution.

TO LIGHT LED

An electric current must flow from one electrode ot another to complete the circuit. If ions are present in a solution the movement of ions toward the positve and negative lectrodes estalbishes the electric current.

WEAK ELETORLYTE solution

Cotnains a small number of ions and the LED IS DIMLY LIT.

NON ELECTROLYTE solution

Contains no ions, LED will not light.

Identify common structural features of EHTANOL AND 1-DECANOL.

#NAME?

HEXANE IS NON POLAR because the CARBON AND HYDROGEN ARE SYMMETRIC. Polar does not DISSOLVE IN NON POLAR. 1-DECANOL doesn't not dissolve in water because it is MUCH LARGER AND THE LONDON FORCES are too STRONG for water to dissolve it.

...

COMMON FEATURES OF toluene and NAPHTHALENE.

They both have the BENZENE RING. Toluene is NOT a POLAR MOLECULAR it CANNOT DISSOLVE IN WATER which IS POLAR. There is not enough DIPOLE MOVEMENT TO MAKE IT SOLUBLE IN WATER. Toluene only dissolves i n HEXANE BECAUSE THEY ARE BOTH NON POLAR and they have similar intermolecular FORCESS.

NAPHTHALENE HAS TWO BENZEN RINGS. They fused together and it is a STABLE MOLECULE. It is considered NONPOLAR because of this and will not dissolve in water which is POLAR. IT DISSOLVES IN HEXANE.

...

Which are ABLE TO HYDROGEN BOND WITH WATER?
-Ethanol,
-1-decanol
-Glycerin
-Sucrose
-Urea

Ethanol, Glycerin, Sucrose, and Urea are able to BECAUSE THEY HAVE OH BONDS OR NH BONDS. Ethanol, GLYCERIN, SUCROSE HAVE OH BONDS. and NH is in UREA. These bonds will form HYDROGEN BONDS and allow the compounds to DISSOLVE IN WATER. Ethanol, glycerin, sucrose, and urea are POLAR AND CANNOT DISSOLVE IN HEXANE HEXANE DOES NOT HAVE HYDROGEN BONDING. The bonding will only occur in OH or NH gropus.

What feature is common to ALL SALTS THAT ARE SOLUBLE IN WATER?

All salts have an IONIC FEATURE. It is made up of POSITIVE AND NEGATIVE IONS, so there are opposite charges that will bond with the OPPOSITE POSITIVE AND NEGATIVE ENDS OF WATER.

What FEATURE IS COMMON TO SALTS which are either only SLIGHTLY SOLUBLE IN WATER or INSOLUBLE?

That the INTERMOLECULAR FORCES in the salts cause the molecules to be more ATTRACTED TO EACH OTHER THAN BONDING with the WATER MOLECULES.

Explain how the DIFFERENCE IN THESE FEATURES accounts for the DIFFERENCE IN SOLUBILITY.

These DIFFERENCES ACCOUNT FOR THE DIFFERENCE IN SOLUBILITY BECAUSE it accounts for the symmetry o the salts. This will determine the polarity and this determines whther the salt will dsisolve in water ( a polar molecular)

STUDY PERCENT BY MASS,
VOLUME OF WATER EVAPORATED,
CONCENTRATION
MOLARITY!!! Pg. 55-61!

...