Solutions chem quiz

Water

odorless, tasteless, transparent, exhibits a bluish tinge

Structure of Water

6 oxygen valence electrons, 2 oxygen unpaired electrons, 1 hydrogen valence electron (bent 105)

Unusual Property: High Surface Tension

water molecules have high polarity and high surface tension

high cohesion at the surface creates a “skin”

water has such high surface tension that it can support objects floating on it

Surfactant

something that gets in the way of hydrogen bonding and breaks down the surface tension

Capillary action (surface tension cont)

how water moves through plant stems and how straws work

one molecule pulls the other molecules up because of polarity (uses cohesion and adhesion at the same time)

Unusual Property: High Boiling Point

Strength of cohesive force at the top is extra strong because of the high temp

because water is polar!

Unusual Property: Solid is less dense than liquid water

if you put ice in water it will float (usually solid form in liquid form would sink)

this is because water has a bent structure

when water molecules become solid they line up in a lattice structure

Unusual Property: Water is the universal solvent

water is the most polar substance

it has the ability to dissolve or break down other polar substances

“like dissolves like”

Polarity

a polar molecules has an uneven distribution of electrons, creating a “more positive” and a “more negative” end

Cohesion

How molecules stick to each other

Adhesion

How molecules stick to other things

Hydration

solvation (dissolving) when water is the solvent

Solute

substance that gets dissolved

Solvent

substance that does the dissolving

Solution

contains solute and solvent

Solvation

Fancy word for dissolving

“Like dissolves like”

Polar dissolves polar

non polar dissolves non polar

Intramolecular Force

are the bonds within the molecule

Intermolecular force

forces of attraction between molecules due to polarity and movement of electrons within the bond

effect of IMF on boiling and melting point

The stronger the IMF, the more energy is required to melt a solid or boil a liquid

The weaker the IMF, the less energy is required to melt a solid or boil a liquid

Effect of IMF on viscosity

viscosity increases with a stronger IMF, and decreases with a higher temperature

viscosity is the resistance of a liquid to flow (liquids that are viscous flow more slowly than liquids that are not viscous)

Hydrogen Bonding

between covalents

the hydrogen in one of these molecules has a highly localized positive charge due to electronegativity of F, O, N

Ion-Dipole force

strongest force

exist between an ionic compound in water

London Dispersion Force (LDF)

weakest force

exists between all molecules

it is a temporary attractive force that is created when adjacent electrons are positioned in a way that makes the atoms form temporary dipoles

noble gasses, diatomic, non-polar substances have strong LDF

factors that effect LDF:

number of electrons in atom (more electrons, more LDF)

Size of atom or molecule (main factor)

Shape of molecules with similar masses (more compact less LDF

DP-DP force

most common IMF

oppositely charged ends attract each other

Rate of Solvation

the speed/process by which solvent molecules surround and interact with solute molecules

Factors effecting rate of solvation

stirring/ shaking: increasing contact between solute and solvent therefore dissolving is faster

temperature: high temp→high energy→high movement→ high collisions→so more contact with solute and solvent → so dissolves faster

Particle size: smaller particles → way more surface area → more solute exposed to solvent → quicker dissolving will happen

Solubility

the amount of solute that can dissolve in a given amount of solvent at a certain temperature

unit: g solute / 100 g solvent

Pressure effect on solubility

solids: n/a

gasses: high pressure, high solubility and low pressure, low solubility

Temperature effect on solubility

solids: temp increases, solubility increases

gasses: temp increases, solubility decreases

Saturation

deals with the number of solute particles that are dissolved in a solvent at a given temperature

Saturated solution

max amount of solute that can be dissolved at given temp

Unsaturated Solution

less solute than it could theoretically hold at given temp

Super Saturated Solution

through a process, make a saturated solution at a high temp, and the solution will hold more solute than it theoretically can at given temp

properties of a solution

homogenous (looks same/tiny particles), negative tyndall effect (light goes straight through), clear (doesn’t mean colorless, means you can see through it), couldn’t be filtered, like dissolves like

concentration

amount of solute in a solution to either the solvent or the total solution

Concentrated solution vs Dilute solution

concentrated- max amount of solute (strong and saturated) and dilute- small amount of solute (weak and unsaturated)

Molarity

Molarity (M) = Moles of solute / Liters of solution

molality

molality (m) = Moles of solute / kilograms of solvent

solution stoich steps

1: M = Moles/L

2: moles from previous step | moles unknown

moles given

3: M unknown = moles unknown (previous step)

L unknown

Colligative Property

a property that depends only upon the number of solute particles and not upon their identity

Boiling Point Elevation

the difference in temp between a boiling point of solution and the boiling point of the pure solvent (+)

Freezing-Point Depression

the difference in temp between a freezing of solution and the freezing point of the pure solvent (-)

freezing and boiling point of water

freezing: 0 degrees C

boiling: 100 degrees C