Aqueous Solutions

Properties of Water:

-Exists as a liquid at STP -Water has a LOW vapor pressure (doe not evaporate easily) -Pure water is odorless and tasteless -Since O is more EN than H, the electrons spend more time with O than H -Bent shape geometry -POLAR molecule (because of its shape)

Factors Affecting Solubility

1) As temperature INCREASES, the solubility of a SOLID in a liquid increases 2) As temperature INCREASES, the solubility of a GAS in a liquid decreases 3) As pressure INCREASES, the solubility of a GAS in a liquid increases

Adhesion

Molecules of water "stick" to the container

Cohesion

Molecules of water "stick" together

Water (H2O)

One 'O' and 2 'H' atoms connected by COVALENT bonds

Solute

Substance that is dissolved

High Surface Tension

Surface of a LIQUID resists an external force

Solubility

The amount of solute that will dissolve in a particular amount of solvent

Boiling Point Elevation

The boiling point of a solution is always HIGHER than the boiling point of a pure solvent.

Solvent

The dissolving medium (what the solute is dissolved in)

Molarity (M)

moles of solute per LITER of solution Molarity (M) = moles SOLUTE / liters SOLUTION

Molality (m)

moles of solute per kg of solvent Molality (m) = Moles SOLUTE / kg SOLVENT

Water does NOT dissolve oil based substances

HYDROPHOBIC = WATER FEARING

Concentrated

Has a LARGE amount of solute particles in a given amount of solvent

Dilute

Has a SMALL amount of solute particles in a given amount of solvent

Hydrophilic (ionic and polar) will dissolve in water (MOSTLY!!)

Hydrophobic (non-polar) will NOT dissolve (MOSTLY!!!)

Soluble

Indicated that a SOLID substance will dissolve in another substance (usually a liquid like water)

Immiscible

Indicates that a LIQUID will NOT dissolve in another liquid

Miscible

Indicates that a LIQUID will dissolve in another liquid

Insoluble

Indicates that a SOLID substance will NOT dissolve -technically it is not "insoluble" a small amount actually DOES dissolve but it is so small of an amount it is considered to be "insoluble"

Dilutions:

1) To dilute a solution (make it LESS concentrates) you need to INCREASE the amount of SOLVENT! (water down) 2)Since the TOTAL number of MOLES of solute still remains the same in solution (only the amount of solvent and total solution changes) then the following is true: -Volume in LITERS x MOLARITY (mol/L) = moles solute.

Factors Affecting Solution Formation

1) particle size- smaller particles tend to dissolve faster 2) heat (temperature) 3) stirring/ agitation 4) "like dissolves like"

Solution

A homogenous mixture of a substance dissolved in another substance

Aqueous Solution

A solution where the solvent is water

NaCl dissolves in water because the interaction between water and the dissociated ions in solution is MORE STABLE and LOWER ENERGY than when NaCl is bonded together as a ________

Compound

Water has a maximum density of 1.00 g/cm^3 at 3.98 degrees C Making it one of the ONLY substances whose solid form

FLOATS in its own liquid

Water undergoes extensive HYDROGEN BONDING

H of one molecule bonds to the lone pair of electrons on the O of another molecule -HIGH ATTRACTION between 2 water molecules

Water is a very good SOLVENT for most polar and ionic substances

HYDROPHILIC = WATER LOVING)

Freezing Point Depression

The freezing point of a solution is always LOWER then the freezing point of a pure solvent

As a solute dissolves in a solvent the particles of the solute become 'solvated' (surrounded by water molecules in a particle formation) and there is an ATTRACTION from solute to solvent.

The more the attraction is, the HARDER it is to separate the solvent from the solute (so the boiling point INCREASES!) i is the number of particles per molecule or formula unit of solute

Solvation

The process by which solute particles become surrounded by solvent molecules as they go into solution

Henry's Law:

The solubility of a gas on a liquid at a given temperature is DIRECTLY proportional to the gas above the liquid

Water is known as the 'universal solvent'

Universal Solvent meaning it is the most commonly used That does NOT mean that water dissolves everything!!

Since the moles of solute before and after are the same:

V1C2 = V2C2

Capillary Action

Water has a tendency to move up a narrow tube AGAINST the force of gravity

PURE water does NOT conduct electricity very well (poor conductor) (but with ions, minerals, or other things dissolved in it, it DOES conduct electricity)

Water has the 2nd HIGHEST specific heat (ammonia is the 1st) (this means it HOLDS LOTS of heat before changing its temperature)

Unsaturated

contains LESS THAN the maximum amount of solute in a particular amount of solvent.

Supersaturated

contains MORE THAN the max amount of solute in a particular amount of solvent.

Saturated

contains the maximum amount of solute in a particular amount of solvent.

Colligative Properties

depends ONLY on the number of particles of solute dissolved in a given mass of solvent (not on the identity of the solute)

Serial DIlutions

dilutions are done in a SERIES (one after the other) in order to make a very small concentration that would not be convenient to make in one step.

Concentration

how much solute is dissolved in a particular amount of a solvent or solution

As a solute dissolves in a solvent the particles of the solute become 'solvated' (surrounded by water molecules in a particular formation) the solute particles take up space that is normally occupied by water molecules forming a crystalline structure so it makes it more difficult for the solid structure to form.

i is the number of particles per molecule or formula unit or solute!!

percent by volume

the grams of solute per mL of solution (expressed as a percentage) Percent by Vol. = (g SOLUTE / mL SOLUTION) x 100