and Organic ChemistryLast Module!!

Key Terms

• Solution• Aqueous solution• Dipole-dipole attraction• Ion-dipole attraction• Solute• Saturated• Solubility • Hydrogen bonding

Solvent

Unsaturated

Alloy

electrolyte

Solutions• Solutions are ____________________ of two or

more pure substances.• In a solution, the _______ is dispersed uniformly

throughout the ______________.• Solvents are usually present in larger amounts

than solutes• Solutions have ___________________________,

they can exist in different ratios eg. Tea• When a solute dissolves in a solvent, no chemical

reaction occurs• Solutions can be __________________________

Composition of air: N (78%), O (21%), Ar (0.9%) and CO2 (0.03%)

Aqueous Solutions• Water is the __________________• Water is:

• Ethanol• Liquids that do no dissolve in one another are

_________________• Oil and water

Alloys• _______________• _______________• Adding another

element to a metal ____________________________________

• Bronze is an alloy of copper and tin

• Bronze is stronger than copper and can be melted in ordinary fire

Solubility and Saturation

• The ability of a solvent to dissolve a solute depends :

• Why temperature?

Solubility of NaClat 20o C

• 20g of NaCl dissolve to form an unsaturated solution

• 36g of NaCl dissolve to form a saturated solution

• 40g of NaCl forms a saturated solution and 4g of precipitate

A saturated solution:

An unsaturated solution:

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

Sodium acetate crystals rapidly form when a seed crystal isadded to a supersaturated solution of sodium acetate.http://www.youtube.com/watch?v=XSGvy2FPfCw&feature=related

Factors that Affect Rate of Dissolving and Solubility

• A. ___________--brings more fresh solvent into contact with more solute.

• B. _______________ the solute into smaller size particles. Smaller particles have more surface area than larger size particles. Since dissolving occurs at the surface of the solute, this allows more solvent to come in contact with more solute.

• C. ________________________-this speeds up the particles and increases the rate of contact between solvent and solute particles.

The Process of Dissolving at the Molecular Level

• 1. _____________________________________________________________ Requires energy. In an ionic solid, the forces that are holding the ions together must be broken. In a molecular solid, the forces between the molecules must be broken.

• _________________________________________________________________-This also requires energy.

• There is an _________________________________________________________________ This step gives off energy.

Important!

• When the forces of attraction between _______________ in a mixture are ___________ than the forces of attraction of ____________________, a solution forms

• The strength of each attraction influences the solubility,

How Does a Solution Form?1. Solvent molecules attracted to surface ions.2. Each ion is surrounded by solvent molecules.1. http://www.youtube.com/watch?v=EBfGcTAJF4o&feature=r

elated

Ionic solid dissolving in water

“like dissolves like”Two substances with similar:

• 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)12.2

Dipole-Dipole Attractions

• Intermolecular• Usually only 1% as strong as ionic or covalent bonds.

Hydrogen Bonding in Water

• Between the H molecule on one water molecule and the O molecule of another water molecule.

• Stronger than regular dipole-dipole attraction, but much weaker than the covalent bond intramolecularily between O and H.

• Water is sticky!

Ion-Dipole Attractions

• The _______________of the water dipole is attracted to the _____________ on the surface of the ionic crystal compound.

• The ________________of the water dipole is attracted to the ____________

• Ion-dipole attractions=

• Generally, _____________________________________• When ions are present in an aqueous solution, they are said

to be ___________________• Hydrated ions can conduct electricity in water =

__________________________

How Does a Solution Form?

The ions are solvated (surrounded by solvent).

If the solvent is water, the ions are hydrated.

The intermolecular force here is ion-dipole.

Hydrated Calcium Ion

An electrolyte is a substance that, when dissolved in water,

A non-electrolyte is a substance that, when dissolved,

http://www.youtube.com/watch?v=aELPrWzixeU&feature=related

nonelectrolyte weak electrolyte strong electrolyte 4.1

Electrolytes

• Your body fluids -- blood, plasma, interstitial fluid (fluid between cells) -- are like seawater and have a high concentration of sodium chloride. The electrolytes in sodium chloride are:

• sodium ion (Na+) - cation • chloride ion (Cl-) - anion

Electrolytes

• As for your body, the major electrolytes are as follows: sodium (Na+)

• potassium (K+) • chloride (Cl-) • calcium (Ca2+) • magnesium (Mg2+) • bicarbonate (HCO3

-)

• phosphate (PO42-)

• sulfate (SO42-)

Electrolytes

• Electrolytes are important because they are what your cells (especially nerve, heart, muscle) use to maintain voltages across their cell membranes and to carry electrical impulses (nerve impulses, muscle contractions) across themselves and to other cells. Your kidneys work to keep the electrolyte concentrations in your blood constant despite changes in your body. For example, when you exercise heavily, you lose electrolytes in your sweat, particularly sodium and potassium.

Predicting Solubility

• DEN!

Solubility of Covalent Compounds

• Except: methanol, ethanol, and sugars….why?• These molecules have polar bonds which can

form hydrogen bonds with water• They become ____________________• They are ________________________

Sucrose

Insoluble Covalent Bonds

• Eg. Oil and grease

“like dissolves like”Two substances with similar intermolecular forces are likely to be soluble in each other.

12.2

Factors that affect solubility1. Molecule Size

• Alcohols have OH groups that form bonds with H

• The larger the molecule,

• Table 8.2 pp. 295

Factors that affect solubility2. Temperature

Heat Pollution

• O concentration in the water decreases

• Fish and plants don’t have enough O to breathe.

Pressure and Solubility

• An unopened bottle of soda pop feels firm due to the high pressure inside and contains a lot of gas dissolved in the soda pop. If you remove the cap from the bottle you suddenly see bubbles of gas appearing in the soda pop. When you remove the cap the pressure on the solution of soda pop decreases and the gas that was dissolved in it, no longer can stay dissolved and comes out of solution.

Homework

• Read about “The Bends” on pg. 299• All questions from Lessons 1 & 2• Self-Check #1• Readings for Monday: Lesson 3 & 4