solutions

i love chemistry chem is warm and fuzzy/her slides suck i hate that woman shes so annoying LOL

what is water

what is water

It is a Polar Molecule with one positive end (hydrogen) and one negative end (oxygen)

why is water the most effective solvent?

because it is highly polar

what can water dissolve

ionic and polar compounds (water cannot dissolve nonpolar compounds)

what does water’s polarity mean

it has a positive and negative end

example of dissolving water and salt

• When mixed with salt, NaCl, water’s negative end (oxygen) is attracted to NaCl’s positive end (Na)

• Water’s positive end (hydrogen) is then attracted to NaCl’s negative end (Cl)

Solubility

The ability to dissolve a solute in a solvent to form a solution, a homogeneous mixture

Solute

The matter dissolved in a solvent

solvent

The matter in which a solute is dissolved

solution

Homogeneous mixture

Aqueous Solutions

solution where water is the solvent

what is solubility heavily based upon

polarity!

“like dissolves like”

means that substances with the same polarity dissolve each other

Ionic compounds dissolve in

polar solvents

Polar compounds dissolve in

polar solvents

Non-polar compounds dissolve in

nonpolar solvents

why dont water and oil mix

oil is nonpolar, water is polar

what are the factors affecting solubility

temperature and pressure

As temperature ↑, solubility of liquids and solids

↑

As temperature ↑, solubility of gases

↓

As pressure ↑, solubility of liquids and solids is

unaffected

As pressure ↑, solubility of gases

↑ (in a liquid)

• think about a soda bottle being the fizziest the moment you open it

Dissolution Rate

It’s the rate at which the solute dissolves in the solvent

kinetic energy affecting dissolution rate

• As kinetic energy increases, so does the dissolving rate

• The opposite is true too!

collisions affecting dissolution rate

• As the number of collisions increases, so does the dissolving rate

• The opposite is true too!

Temperature is a measure of

kinetic energy

By increasing the heat, the kinetic energy goes up and so does the

speed of the particles

More speed =

more collisions

Breaking a solid into smaller pieces greatly increases

its surface area

More surface area =

smaller particles

Rate of collisions increases as surface area

increases

Agitation is

applying a force to create motion between the solute and solvents

does agitation increase the chance of collisions?

yes!

• As the solvent moves around, more collisions occur between solvent and solute particles

3 ways to dissolve solid solute faster

1. More Agitation

2. Increasing Surface Area

3. Increasing Temperature

2 ways to dissolve gases faster

1. More Pressure

2. Lower Temperatures

above the solubility line is

supersaturation

below the solubility line is

unsaturated

on the solubility line is

saturated

Saturated Solutions

Containing the maximum amount of dissolved solute that the solution can hold. It is the curve of the graph

• no more solute dissolves

Unsaturated Solutions

Contain less dissolved solute and can dissolve more solutes! It is underneath the curve of the graph

Supersaturated Solutions

Contain more dissolved solute than the saturated solution can dissolved. It is above the graph of the curve

• becomes unstable, crystals form

key things to know about solubility curves

• grams of solute vs temperature

• multiple lines

• lines rep diff substances

• solubility is typically based on 100g of water

What is Concentration?

a measure of how much solute dissolved in a specific amount of solvent or solution

The higher the concentration..

the more solute within the solution

dilution is the ___ of concentration

opposite (think of it like a timeline)

molarity

measure of concentration

• moles of solute per liter of solution

molarity misconception

Molarity measures the moles of the solute per 1 liter always. So if you see 12M, that is 12 moles of the solute per 1 liter (12 moles / 1 liter)

molarity equation

m=(n/L)

What does it mean to dilute a solution?

Solutions can be diluted simply by adding water and leaving the amount of solute unchanged

What happens to molarity when a solution is diluted?

• More water has been added, so the total volume of solution is greater but the amount of solute is the same

• Molarity will decrease!

do number of moles change when diluting a concentration?

no, only volume and molarity

How to Measure out Dilutions

m1v1=m2v2

stock solution

The initial molarity and volume

diluted solution

final molarity and volume

The initial molarity tends to be ____ than the final molarity

bigger

the initial volume tends to be ____ than the final volume.

smaller

Intermolecular forces

Attractive forces between molecules that are weaker than bonds

what do intermolecular forces do

make individual molecules stick together and limits their motion

types of IMF from weakest to strongest

london dispersion forces, dipole-dipole forces, hydrogen bonds, ion-dipole forces

type of imf depends on..

polarity! determine if the bonds are polar or nonpolar

if the electron cloud is shared equally it is

nonpolar (en<.3)

if the electron cloud is shared unequally it is

polar! (en>.3)

dipole

slight pos and neg charges on the ends of the molecule

positive dipole means

less electronegative atom

negative dipole means

more electronegative atom

Nonpolar molecules

no normal charges or dipoles ( small EN  difference)

london dispersion forces/vanderwaals

very weak attractive forces between

nonpolar molecules

-normally nonpolar molecules

-temporary dipoles

-attract and stick together

dipole-dipole forces

-polar covalent

-polar molecules - unequal sharing of electron cloud (permanent dipoles)

more polar molecules=

stronger dipole-dipole force

hydrogen bonds

like dipole-dipole except must have H bonded to the highly EN elements

what gives water many of its properties

strong hydrogen bonds between water molecules

What Are Colligative Properties?

the properties of a solvent that change due to the presence of a solute

-It also depends on the concentration of solute particles

whats the point of colligative properties

By adding a solute to the solvent (like salt to water), the properties of your solvent (water) might change

colligative property examples

freezing point depression, boiling point elevation, osmotic pressure, vapor pressure

osmotic pressure

Osmotic pressure varies depending on the solute being added

vapor pressure lowering

The pressure exerted by the gas of the solution is lower

what are electrolytes

solutions that conduct electricity due to dissolved ions caused by dissociation of ionic compounds

can electrolytes vary in strength

yes

Nonelectrolytes do not

conduct electricity

why is salt an electrolyte when dissolved in wate

salt dissociates into sodium and chlorine ions, allowing electricity to flow through it

how to determine if its an electrolyte

has a solute that is an ionic compound (dissolves in water) (check the solubility chart)

When ionic compounds dissolve, in water..

they dissociate (meaning they break down into ions)

nonelectrolytes either

• contain polar covalent compounds

• have ionic compounds that do not dissolve

strong electrolytes are

• strong Acids

• Strong Bases

• Ionic Compounds

Weak electrolytes are…

-weak acids

-weak bases