CHE 116 - Exam 4

Solution

a special type of homogenous mixture composed of two or more substances

Solvent

substance that does the dissolving; larger amount

Solute

substance that gets dissolved; smaller amount

Solubility

maximum amount of solute that can dissolve in an amount of solvent at a specific temperature

Solvation

not just dissapearing, its a tug-of-war involving intermolecular forces

Polar Solvents

solvates polar solutes (sugar) or ionic (salts)

Non-polar Solvents

solvates non-polr solutes (oil or grease)

Enthalpy

(ΔH) — negative (release heat) and determines if “bond swapping” is favorable

Entropy

(ΔS) — positive (increase disorder) and a driving force that allows endothermic solutions to exist

Tug-Of-War

lower energy (-ΔH) and higher disorder (+ΔS) => ideal scenario

Saturated Solutions

less than capacity, stable and dissolves (ex. weak tea)

Saturated Solutions

at full capacity, stable and sinks to the bottom (ex. tea with sugar at the bottom)

Supersaturated Solutions

more than capacity, unstable and triggers mass crystallization (ex. ‘snap’ hand warmers or rock candy)

Dipole-dipole/ Hydrogen bonding

polar + polar = soluble

London dispersion

nonpolar + nonpolar = soluble

Ion-dipole

ionic + polar = usually soluble

Non IMF

nonpolar + polar = insoluble

Miscible

mixes completely, similar properties (ex. food coloring and water)

Immiscible

separates into layers, different polarities (ex. gasoline and water)

Henry’s Law

double the pressure, double to solubility

C = kP_gas

Solubility of solid

temperature and solubility increases and heat breaks the solids internal bonds

Solubility of gas

temperature increases, solubility decreases, and heat gives gas the energy to escape the liquid

Vapor Pressure Lowering

when adding solute to a solvent, the vapor pressure decreases (ex. saltwater pool evaporates more slowly than a freshwater pool).

Boiling Point Elevation

vapor pressure is low, the solution must be heated to a higher temperature (ex. adding salt to water when cooking pasta)

Freezing Point Depression

solute particles fit between solvent molecules and disrupts the formation of solid crystal (ex. spreading salt on icy roads)

Colloid

heteogeneous mixture that sits in the middle of a solution

Hydrophilic

spontaneous, stable, thick layer of water (solvation)

Hydrophobic

requires energy, unstable, surface change (repulsion)

“like dissolves like”

polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes

Colligative properties

characteristics of a solution that depend only on the number of solute particles present, not their chemical identity.

Ethylene glycol

s a molecular (covalent) compound, so it does not ionize in water. Therefore, i = 1

Molarity

M = moles of solute / liters of solution

Chain Length

the longer the length, its harder to become soluble

-NH₂

amino (amine)

-OH

hydroxyl (alcohol)

-COOH

carboxyl (carboxyl acid)

-CHO

aldehyde (aldehyde)

-COC

carbonyl (ketone)

London dispersion forces

the melting and boiling points of alkane are determined by

Chiral centers

atom bonded— usually carbon — that is bonded to four different groups

-ol

alcohol (4 groups)

-al

aldehyde

-one

ketone (3 groups)

-oic

carboxyl group

-oate

ester (2 atoms)

-amide

amides

-ene

alkenes