chem final term 1 gr11b

suspension

a mixture from which particles settle out upon standing

ex. if u shake a container containing a piece of clay ( dispersed phase ) nd water ( dispersed medium ) the clay breaks into fine particles and the water becomes cloudy bc the clay particles are suspended in the water, if u stop shaking the particles settle down

whats the difference between a suspension and a solution

• the particles of a suspension are much larger and do not stay suspended indefinitely

• a solution is homogeneous, a suspension is heterogeneous because at least two substances can be clearly identified

colloid

a heterogeneous mixture containing particles that range in size from 1nm to 1000nm

the particles are spread, or dispersed, throughout tge dispersion medium, which can be a solid, liquid, or gas

what distinguishes a colloid fron a suspension and a solution

colloids have particles smaller than those in suspensions and larger than those in solutions, colloids cannot be filtered, and the particles do not settle out with time

tyndall effect

the scattering of visible light particles in

brownian motion

the movement of colloid particles that cause flashes of light (scintillations) that are seen when colloids are studied under a microscope

its caused by collisions of the molecules of the dispersion medium with the small, dispersed colloidal particles

they scintillate because the particles reflect and scatter the light as they move erratically

coagulation

occurs when the charge (from adsorbing ions) on colloidal particles is neutralized by adding smth that cancels out the charge so the particles start to clump tgth

ex. adding lemon juice to milk so the milk starts clumping

how can a colloidal system be destroyed / coagulated

the addition of electrolytes

the added ions neutralize the charged colloidal particles

emulsion

a colloidal dispersion of liquid in a liquid, the process of mixing two immiscible liquids (liquids that dont mix ex. oil nd water)

emulsifying agent

a substance that helps mix two immiscible liquids and stabilize the mixture by reducing surface tension and preventing seperation ex. adding soap to oil and water to emulsify them

how does an emulsifying agent work

Soaps and detergents have molecules with two different ends—one that’s attracted to water and the other to oil. This allows them to help form a stable mixture (emulsion) of water and oil, which normally don’t mix.

what factors effect whether or not a substance will dissolve ?

the composition of the solvent and solute ( like dissolves like )

factors that affect how fast a substance dissolves

agitation (as in shaking/mixing it tgth)

temperature

particle size of the solute (substance being dissolved)

temperature

at higher temperatures, the kinetic energy of water molecules is greater than at lower temperatures, so the molecules move faster

particle size of the solute

the more surface area of the solute that is exposed, the faster the rate of dissolving

saturated solution

a solution that contains the maximum amount of solute for a given quantity of solvent at a constant temperature and pressure, any additional solute will remain undissolved.

how can u describe the equilibrium in a saturated solution

a state of dynamic equilibrium exists between the solution and any undissolved solute provided that the temperature remains constant

dynamic equilibrium means that there are two processes happening at the same time at the same rate so there is no overall change:

dissolving - solute particles are dissolving into the solution

crystalization - some dissolved particles are coming back and becoming solid again

solubility

the amt of solute that dissolves in a given quantity of solute that dissolves in a given quantity of a solvent at a specified temp and pressure to produce a saturated solution

expressed in grams of solute per 100g of solvent ( g/ 100g of h2o)

the solubility of a gas is expressed in grams per liter of solution (g/L)

unsaturated solution

a solution that contains less solute than a saturated solution, if additional solute is added to an unsaturated solution, the solute will dissolve until the solution is saturated

miscible

two liquids that can dissolve in each other

immiscible

two liquids that cannot dissolve in each other

what factors affect the solubility of a substance

temperature affects solid liquid and gaseous solutes

temperature and pressure affects only gaseous solutes

supersaturated solution

contains more solute than it can usually hold at a given temperature

the excess solute stays dissolved but becomes unstable

if disturbed (adding a seed crystal or stirring, etc.) the extra solute will crystallize

henrys law

at a given temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid

S1/P1 = S2/P2

concentration

a measure of the amt of solute that is dissolved in a given quantity of solvent

dilute solution

a solution that contains a relatively small amt of solute

concentrated solution

contains a large amt of solute

Molarity

the number of moles of solute dissolved in 1 liter of solution

also known as molar concentration

M = moles of solute / liters of solution

what effect does dilution have on the amount of solute

diluting a solution reduces the number of moles per unit volume but the total number of moles of solute in solution does not change

moles before dilution = moles after dilution

how to calculate moles of solute from molarity

moles of solute = M1V1 = M2V2

M - molarity

V - volume

percent by volume

volume of solute / volume of solution X 100%

percent by mass

mass of solute / mass of solution X 100%

colligative properties

a property of solutions that depend only upon the number of solute particles not upon their identity

• low vapor pressure

• freezing point depression

• boiling point elevation

vapor pressure

the pressure exerted by a vapor that is in dynamic equilibrium with its liquid in a closed system

a solution that contains a solute is nonvolatile ( not easily vaporized ) always has a lower vapor pressure than the pure solvent

freezing point depression

when a substance freezes, the particles of the solid take on an orderly pattern, the presence of a solute in water disrupts the formation of this pattern, as a result, more kinetic energy must be withdrawn from a solution than from the pure solvent to cause the solution to solidify

the freezing point of a solution is lower than the freezing point of the pure solvent

the difference in temperature between the freezing point of a solution and the freezing point of the pure solvent is called the freezing point depression

boiling point elevation

the boiling point of a substance is the temperature at which the vapor pressure of the liquid phase equals atmospheric pressure

adding a nonvolatile solute to a liquid solvent decreases the vapor pressure of the solvent

because of the decrease in vapor pressure, additional kinetic energy must be added to raise the vapor pressure of the liquid phase to initiate boiling

the boiling point of a solvent is higher than that of the pure solvent

the difference in temperature is the boiling point elevation

molality

m = moles of solute / kilogram of solvent

whats the difference between molality and Molarity

molality refers to moles of solute per kilogram of solvent

Molarity refers to moles of solute per liters of solution (big M big solution)

molality is represented as m and molarity is represented as M

mole fraction

the mole fraction of a solute in a solution is the ratio of the moles of that solute to the total number of moles of solvent and solute

freezing point depression rule

Tf = Kf x m

Kf is the molal freezing point depression constant (teacher will provide)

boiling point elevation rule

Tb = Kb x m

Kb is the molal boiling point elevation constant