ib chem concepts

so far, includes topics 1, 2, 3, 4, 5, 6, 7, 8

pH is a measure of?

H+ ion concentration

a Brønsted-lowry acid is a

proton (H+) donor

a Brønsted-lowry base is a

proton (H+) acceptor

an alkali is a

soluble base

amphiprotic species

can act as either Brønsted-lowry acid or a base

conjugate acid-base pair

consists of two substances related to each other by movement of proton

what is the maximum number of electrons that can occupy a p-orbital?

2

non-metal oxides tend to be?

acidic

metal oxides tend to be

basic

what is the main interaction between liquid CH4 molecules?

london dispersion forces

(because EN of C and H are so close, they are non-polar, so no dipole-dipole interactions)

London dispersion forces

instantaneously induced bond between non-polar molecules (due to uneven distribution of electrons)

dipole-dipole forces

attractions between oppositely charged regions of polar molecules

hydrogen bonding

strong IM force between hydrogen bonded to highly EN atom and another highly EN molecule

van der Waals forces (umbrella term)

a slight IM force of attraction that develops between oppositely charged regions (of nearby molecules)

order the van der Waals forces from weakest to strongest:

london dispersion

compare strength of intramolecular bonds between O2 and O3

O3 has weaker bonds than O2 (which has strong double covalent bond, whilst O3 has one plus one intermediate bond), so requires longer wavelengths to be broken down

first ionization energy

minimum energy required to remove one mole of electrons from atom in gaseous state

explain why FIE of group 2 element is greater than that of group 1 element (2m)

there is increasing number of protons on same number of shells

limitations of hydrogen spectrum model

doesn't represent sub-levels, doesn't take into account interactions between molecules, doesn't consider number of electrons an energy level can fit

how to calculate standard enthalpy change:

bonds broken - bonds made (endo - exo)

temperature

measure of thermal energy (of particles)

heat

transfer of energy from high temp object to low temp

enthalpy change + unit

amount of heat energy absorbed in reaction at constant pressure + kJmol-1

enthalpy

heat content of system at constant pressure

energy formula

q\=mcdeltaT

enthalpy change of formation

enthalpy change when 1 mole of compound is formed from constituent elements

enthalpy change of formation formula

products - reactants

enthalpy change of combustion

enthalpy change when 1 mole of substance reacts completely with oxygen

enthalpy change of combustion formula

reactants - products

bond forming ...

releases energy (exothermic)

bond breaking...

requires energy (endothermic)

hess's law

total enthalpy change is independent of the route taken

sublimation

solid to gas

ideal gas equation, what does R \= ?

pV \= nRT, R \= 8.31

Why do gases deviate from the ideal gas law at high pressures?

molecules have finite volume

what factors affect molar volume of ideal gas?

pressure, temp

What is the trend of electronegativity?

increases across a period, decreases down a group

what is the trend of atomic radius?

decreases across period, increases down group

what is the trend of first ionisation energy?

increases across period, decreases down group

effective nuclear charge

total attraction between electron and nucleus minus shielding electrons (Z - S)

what two groups are in the f block?

lanthanides and actinides

isoelectronic

same number of electrons, different number of protons

electron affinity

energy change when electron is added to atom in gaseous state

trend of electron affinity

increases across period, decreases down group

trend in oxides across a period?

basic to amphoteric to acidic

metallic characteristic trends

decreases across period, increases down group

deposition

gas to solid

unit of molar mass

gmol^-1

avogadros law

equal volumes of gases at the same temperature and pressure contain same number of particles

standard solution

solution of known concentration

ideal gas

a hypothetical gas that perfectly fits all assumptions of kinetic-molecular theory (particles moving in constant random motion, widely spaced etc.)

degrees C to Kelvin

+273

STP (standard temperature and pressure)

273 K and 1 atm (or 100kPa)

volume taken by 1 mole of gas at sTP

22.7dm^3

what is relationship between pressure and absolute temp at constant volume?

directly proportional (gay-lussac's law)

what is relationship between volume and temp at constant pressure?

directly proportional (charle's law)

what is relationship between pressure and volume when temp is constant?

inverse (boyle's law)

what is the the limiting reactant?

reactant that is first used up in reaction

equation linking number of particles, mole quantity and Av. number?

N \= nL

how to calculate percentage of element in molecule

Ar of element/Mr of molecule x 100

how to calculate relative atomic mass, with knowledge of isotope and % abundance

(mass of I1 x % abundance) + (mass of I2 x % abundance)/100

what is mass spectrometer used for?

used to determine ram of element from isotopic composition

Exceptions to the Aufbau Principle (that electrons fill lowest available energy before higher levels)

chromium and copper

what is the emission spectrum of hydrogen?

series of lines showing electron transition between higher to lower energy levels

explain difference between continuous and line spectrum

continuous spectrum shows all wavelengths or frequencies of visible light, while line spectrum shows only certain wavelengths in spectrum

transition to n\=1

UV

transition to n\=2

visible light

why can we see color when adding heat to elements?

energy increases, so electrons jump to higher energy levels, and once they go back down, they emit waves of light

(the difference between energy levels determine wavelengths and frequencies of visible light region, causing us to see certain colors - e.g. shortest frequencies = blue)

electronegativity definition

the tendency of an atom to attract electrons

Do ionic compounds conduct electricity?

no, only when molten or aqueous (yet IC are normally solids under normal conditions)

metallic bond

electrostatic attraction between positive ions and delocalised electrons

covalent bond

electrostatic attraction between shared pair of electrons and positively charged nuclei

coordinate covalent bond

where both bonding electrons come from one atom

what compound has an EN of 1.8, yet is still polar covalent?

hydrogen fluoride

When do resonance structures occur?

When there is more than one possible position for a double bond in a molecule

How are the shapes of molecules determined?

vsepr theory

which atoms may form stable compounds with incomplete octets of electrons?

Be and B (+ hydrogen, phosphorus, sulfur)

VSEPR theory

pairs of electrons will repel from each other as far as possible, hence a molecule will adopt shape that minimizes repulsion

linear geometry bond angle, number of electron domains

180 degrees, 2 electron domains

trigonal planar bond angle, number of electron domains

120 degrees, 3 electron domains

tetrahedral bond angle, number of electron domains

109.5, 4 electron domains

trigonal pyramidal bond angle

107 (due to strength of the lone pair of electrons)

bent shape and angle

105

net dipole movement

overall direction electrons are being pulled (μ)

allotropes

different forms of the same element

allotropes of carbon

diamond, graphite, fullerene

what is the difference between amphiprotic and amphoteric?

amphiprotic species can act as both bronsted-lowry acids and bases, while amphoteric can just act as acid or base (e.g. Al2O3 is amphoteric but not amphiprotic)

what is a lewis acid?

species that accepts pair of electrons

what is a lewis base?

species that donates pair of electrons

for collision theory to work, particles must…

collide with correct orientation and sufficient energy to overcome energy barrier for reaction ( i.e. activation energy)

activation energy (***E*****a)**

minimum energy colliding particles must have for reaction to take place

what happens at the transition state?

(highest energy state) where new bonds are formed at same time as old bonds are broken

rate of reaction definition

change in concentration of reactant or product per unit time

rate of reaction formula + unit

change in concentration/change in time, moldm^-3s^-1

what are catalysts?

they increase the rate of reactions by providing alternative pathways that have lower activation energy

what are the four different experiments for rates of reaction?

measuring volume of gas produced, measuring change in ion concentration, measuring time taken for formation of precipitate, measuring change in concentration by titration

acid + metal →

salt + hydrogen (redox reaction)

when is hydrogen not produced in a redox reaction?

when metal is below hydrogen on reactivity series (e.g. copper or silver)

how can hydrogen be tested?

igniting gas, squeaky pop if present

acid + metal oxide/hydroxide →

salt + water