IB Chem SL

relative atomic mass (Ar)

weighted mean of all the naturally occurring isotopes of the element (g/mol)

relative molar mass (Mr)

sum of Ar (no units)

Avogadro’s Constant

6.02x10^-23

Empirical Formula

shows the simplest whole number ratio of atoms of each element in a particular substance

Molecular Formula

shows the actual number of atoms of each element in a particular molecule or substance

Structural formula

shows the arrangement of atoms and bonds within a molecule

molar ratio

given by the coefficients, it is the ratio of the amounts of reactants and products

density

mass/volume (g/cm^3)

solute

dissolved substance

solution

a transparent, homogenous mixture; solute+solvent

concentration

amount of solute in a known volume of solvent (mol/dm^3)

ideal gas equation

PV\=nRT

R

the gas constant\= 8.314 J/K mol

Electromagnetic spectrum

Spectrum of wavelengths that comprise the various types of electromagnetic radiation.

Continuous spectrum

Spectrum that shows all wavelengths of the section of the spectrum used (eg visible or UV, or ...)

line spectrum

a spectrum showing only certain discrete wavelengths

ideal gas

an imaginary or perfect subtance whose particles are infinitely small and do not interact with each other

Avogadro's law

equal volumes of different gasses at the same temperature and pressure contain the same number of moles

Atom economy

A measure of the amount of starting materials that end up as useful products
(mass of desired product/mass of total product)*100\=%

nucleon

collective term for protons and neutrons

atomic number

equal to the number of protons in the nucleus (and to the number of electrons if atom (neutral))

mass number

\# of protons + \# neutrons

Isotopes

atoms that have the same number of protons, but different number of neutrons

Mass Spectrometer

an instrument used to measure the precise masses and relative amounts of atomic and molecular ions

isotopes used as tracers in medicine for treating and diagnosing illnesses

131 125
I & I
53 53

radioactive elements

unstable elements that decay or break down into different elements

wave equation

c\=lambda * v

electromagnetic radiation

a form of energy that exhibits wavelike behavior as it travels through space

sections of the electromagnetic spectrum

radio waves
microwaves
infrared radiation
visible light
ultraviolet
X-rays
gamma rays

emission spectra

consists of discrete lines that converge towards the high energy end. Characteristic to each element

Aufbau principle

lowest energy orbitals are filled with electrons first

Hund's rule

orbitals within the same sub shell are filled singly first

First ionization energy

the energy required to remove the first electron from a mole of an atom in its gaseous state

atomic radius

usually defined as half the distance between the nuclei of two bonded atoms of the same element

Trend in Atomic radii

-Increases down a group
-decreases across a period

Trend in first ionization energy

-decrease down the group
-increase across period

electron affinity

the energy change when a mole of electrons is added to a mole of atoms in a gaseous state

ionic bond

A strong attractive force resulting from the attraction between oppositely charged ions in a lattice.

properties of ionic compounds

crystalline, high melting point, electrically conductive when melted or dissolved in water

Coordinate bonds

when one atom supplies both the shared electrons to form covalent bond

Valence Shell Repulsion theory (VSEPR)

electrons arranged around the central atoms so they are as far apart as possible

Non-bonded pairs of electrons (when compared to bonded pairs)

are more repulsive

shape of 2 electron domains

linear

shape of 3 electron domains

trigonal planar

shape of 4 electron domains

tetrahedral

bond angle of a linear molecule

180

bond angle in a trigonal planar molecule

120

bond angle in a tetrahedral molecule

109.5

allotropes

different forms of an element ex. diamond, graphite and fullerene

molecular polarity

overall dipole of the molecule (polar bonds do not automatically indicate dipole)

London dispersion forces

temporary instantaneous dipole (b/c unevenly spread electrons since moving), weakest attraction; shown in non polar molecules.

Dipole-Dipole forces

relatively weak attractions between polar molecules ; a form of intermolecular forces

Hydrogen bonding

when hydrogen is bonded to a small highly electronegative element, e- pair is pulled away to electronegative element so it is basically just a proton, then is attracted to non bonding pair of e- on another molecule, resulting in a strong dipole-dipole IMF between molecules

relative strength of intermolecular forces

hydrogen bonding>dipole-dipole>London dispersion forces

Metals

are elements that have delocalized electrons and typically form cations

metallic bond

the attraction between neighboring positive ions with delocalized electrons between and around them

malleable

can be bent and reshaped under pressure

ductile

can be drawn out into a wire

alloy

metallic solid solution (usually made up of more than one metal)

endothermic reaction

bonds in reactants are stronger than bonds in products, so energy is absorbed by the reaction

exothermic reaction

bonds in products are stronger than bonds in reactants, so energy is released by the reaction

calculation of enthalpy change in calorimetry experiment

Heat energy\=mass (m) x specific heat capacity (c) x temperature change (delta T)

specific heat capacity of water

4.18 kJ / kg K

standard conditions

100 kPa, 298 K

define specific heat capacity

energy (in J) required to heat one g of substance by one Kelvin

Hess' Law

enthalpy change for a reaction depends only on the difference between the enthalpy of the products and the enthalpy of the reactants (and is independent of reaction pathway)

standard enthalpy change of formation

enthalpy change when one mole of compound is formed from elements in their standard states

standard enthalpy change of combustion

enthalpy change change when one mole of a substance is completely combusted in oxygen under standard conditions

average bond enthalpy

the energy needed to break one mole of a bond on a gaseous molecule averaged over similar compounds

negative value for enthalpy change

the reaction is exothermic

rate of chemical reaction

increase in the concentration of one of the products per unit time or decrease in concentration of one of the reactants per unit time

Maxwell Boltzmann curve

shows distribution of kinetic energies of a fixed sample of particles at a particular temperature

collision theory

-particles must collide
-must collide with proper geometry/ orientation
-must collide with sufficient energy

activation energy

minimum amount of energy required for a reaction to occur

Factors that affect rate of reaction

-temperature
-surface area
-catalyst
-concentration/pressure

catalyst

increases rate of reaction without being chemically changed themselves

dynamic equilibrium

forward and reverse reactions occur at different rates until equilibrium is reached, then CONTINUE to occur at equal rates

Equilibrium constant (Kc)

K is based on concentrations of all species, raised to the power of their coefficients in the balanced equation.

Le Châtelier's Principle

if a system is subjected to a small change, the equilibrium tends to shift as to minimize effect of change

If product of reaction at equilibrium is removed

equilibrium shifts to the right (to form products)

If concentration of reactant is increased

equilibrium shifts to the right (to form products)

If reaction is exothermic (heat is a product), removing heat

shifts equilibrium to the right, towards the products

If pressure increases on a reaction at equilibrium

shifts equilibrium to the side with less volume (compare \# of moles)

Addition of a catalyst in equilibrium reaction

will have no effect on position of equilibrium

Brønsted-Lowry base

proton acceptor

Brønsted-Lowry acid

proton donor

conjugate base

The species remaining after the acid has lost a proton (acid-H+\=base)

amphiprotic

substance that can act as both an acid and a base

Limitus indicator color

blue in alkaline solutions
red in acidic solutions

phenolphthalein indicator color

pink in alkaline solutions
colorless in acidic solutions

Acid + metal hydroxides

\---\> salt and water

Acid neutralization with metal oxides

forms salt and water

Acids with reactive metals (those above copper in activity series)

form salt and hydrogen

Acids and carbonates react to...

form salt, carbon dioxide, and water

Acids and hydrocarbonates to

form salt carbon dioxide and water

pH

-log[H+(aq)]

pH 0

very acidic

pH 7

neutral

pH 14

very basic

if the H+ ion concentration is 1x10^-4

the OH- concentration is 1x10^-10