AP CHEM UNIT 0

YEAR TWO OF THE BEST CLASS

What is a solution?

What is a solution?

A solution is a homogeneous mixture in which one substance is dissolved in another. (ex: air, brass, salt water)

what are the two parts solutions are made of

solvent + solute

Solute

the substance being dissolved

Solvent

the substance doing the dissolving

aqueous solution

a solution where the solvent is WATER

Dissolve (dissolution or solvation):

• process by which a solute is surrounded by solvent molecules

Dissociation

• process of a solute splitting apart into smaller parts, such as the individual ions that compose the substance.

• dissociation is focused around the formation of ions due to water’s polarity (positive and negative dipoles)

What happens when an ionic solute dissolves in water?

The water molecules collide with the surface of the solid solute.

The attraction between the water molecules and the solute causes the individual ions to separate from the surface of the solid.

The water molecules separate from each other and surround the ions.  The hydrogen end of the water molecule surrounds the anions and the oxygen end of the water molecule surrounds the cations.

.The steps occur continuously as each surface layer of solute is dissolved, leaving the next layer exposed to the solvent.

What determines whether or not a solute will dissolve in a given solvent?

One of the main factors that determines whether or not a solute will dissolve in a solvent is the nature of the solute and solvent. (polarity)

in general:

Polar solvents will dissolve 1. and 2. solutes.

Nonpolar solutes will dissolve __ solvents.

polar, ionic

nonpolar

like dissolves like is not an adequate answer to an frq - explain it in detail

Why do some solutions conduct an electrical current?

Whether or not a solution will conduct an electrical current is determined by whether or not the solute produces ions in solution.

strong electrolyte

Solute completely ionizes in water

-strong acids, strong bases and highly soluble ionic compounds

Weak Electrolyte

Solute only partially ionizes in water

-weak acids, weak bases and slightly soluble ionic compounds

Nonelectrolyte

Solute does not ionize in water

-covalent compounds

What is molarity?

Molarity (M) is a unit of concentration.

The formula for calculating molarity is

mol of solute/liters of SOLUTION

Dilutions process?

Sometimes it is necessary to take a more concentrated solution and dilute it with water to make a less concentrated solution. - use mv=m2v2

-One common way of measuring the concentration of a solution is by Colorimetry or

Spectrophotometry, which analyzing the amount of light a solution absorbs.  An

Intensely blue solution would absorb more light than a less intensely colored solution

dilutions definition

 the process of adding more solvent to dilute a solution, i.e. taking a stock solution and adding solvent to make a working solution

Stock solution

• a solution containing a large amount of solute (also called a concentrated solution)  This is what may be stored in a “stock room” \n

Working solution

a solution containing a small amount of solute (also called a diluted solution).  This is the concentration that is commonly worked with.