Physical Flashcards
rate of reaction equation
amount of reactant used / time
lattice enthalpy of dissociation
enthalpy change when 1 mole of a solid ionic compound is completely dissociated into its gaseous ions under standard conditions.
define catalyst
a substance which increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy without being chemically changed.
What did Niel Bohr discover
Proposed the fixed shells
Explain why atoms don’t collapse in on themselves
2 bonding pairs
0 lone pairs
linear (180)
Mass spectrum of sample
Electrospray - H+ is added so ratio is one unit greater
Electron impact - ratio is still equal
3 ways to measure reaction rates
- timing how long it takes for a precipitate to form (using a black dot under reaction vessel)
- measuring a decrease in mass
- measuring the volume of gas given off
define covalent bond
two atoms share electrons (two non metals)
3 bonding pairs
0 lone pairs
trigonal planar (120)
Nuclear model
Rutherford - 1909
enthalpy change of atomisation of a compound
enthalpy change when 1 mole of a compound in its standard state is converted to gaseous atoms
a high positive entropy value indicates _____ disorder
high levels of
Electron impact
Sample is vaporised and high energy electron fired at it. Knocks off an electron.
units of entropy
JK-1 mol-1
define electronegativity
an atom’s ability to attract the electron pair in a covalent bond
equation for enthalpy change
total energy absorbed - total energy released
3 bonding pairs
2 lone pairs
T-shaped (88)
How does shielding affect ionisation energy
More electrons between the nucleus and outer electrons, the less attraction there is.
diamond structure
each carbon atom is bonded to 4 atoms in a tetrahedral structure
Exothermic definition
energy is given out
types of intermolecular forces
- Van der Waal (induced dipole)
- Dipole-dipole
- Hydrogen bonding
Solid sphere model
Dalton - 19th century
is bond making endo or exo
exothermic - energy is released
enthalpy change of atomisation of an element
enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state
define entropy
a measure of the number of ways that particles can be arranged and the number of ways that energy can be shared out between particles.
features of diamond
- high melting point
- hard
- doesn’t conduct electricity
- won’t dissolve
Standard enthalpy of combustion
Enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions
properties of graphite
- slippery (weak bonds between layers)
- conductive (delocalised electrons)
- high melting points (strong covalent bonds in hexagon sheets)
- insoluble
5 bonding pairs
0 lone pairs
trigonal bipyramidal (120/90)
indicators
methyl orange - red in acid, yellow in alkali
phenolphthalein - colourless in acid and pink in alkali
activation energy definition
the minimum amount of kinetic energy that particles need to react
What did Rutherford discover
Proton and Nucleus
What did James Chadwick discover
Neutron
how to set up a titration
1 - use a pipette to measure out a set volume of unknown concentration into a flask.
2 - add indicator
3 - fill a burette with a known conc of acid
sulfate ion
SO4 2-
Copper electronic structure
1s2 2s2 2p6 3s2 3p6 3d10 4s1
4 bonding pairs
2 lone pairs
square planar (90)
Formula for free energy change
Enthalpy change - (temp change x entropy change)
3 bonding pairs
1 lone pair
trigonal pyramidal (107)
titration method
1 - rough titration to get an idea of end point
2 - accurate titration. add acid until 2cm3 of previous end point then add drop wise.
3 - calculate volume used and repeat
how does increasing temperature impact a MB curve
moves to the right
peak moves down
area must remain the same
Carbonate ion
CO3 2-
first electron affinity
enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole of gaseous atoms
electrode equations in a lithium battery
Positive = Li+ + CoO2 + e- = Li+[CoO2]-
Negative = Li = Li+ + e-
units of enthalpy change
KJmol -1
First ionisation energy
Energy required to remove 1 electron from each atom in 1 mole of gaseous ions to form 1 mole of gaseous 1+ ions.
ideal gas equation
pV = nRT
2 processes which occur when a solid ionic lattice dissolves in water
1 - the bonds between the ions break to give free ions (endo)
2 - bonds between ions and water are made (exo)
first ionisation energy
enthalpy change when 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms
lattice enthalpy of formation
enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions
define free energy
a measure used to predict if a reaction is feasible
do soluble substances have endo or exothermic enthalpies of solution
exothermic
units for ideal gas equation
Pa x m3 = mol x (JK -1 mol -1) x K
area under the Maxwell-Boltzman distribution curve
total number of molecules
enthalpy change of solution
enthalpy change when 1 mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution.
define enthalpy change
the heat energy transferred in a reaction at a constant pressure
Ions and atoms have the same number of
Protons
nitrate ion
NO3 2-
How does nuclear charge affect ionisation energy
The more protons there are in the nucleus, the more positive the nucleus becomes, leading to a stronger attraction with the electrons
what are standard conditions
298K
100 kPa
1M concentration
second ionisation energy
enthalpy change when 1 mole of gaseous 2+ ions is formed from 1 mole of gaseous 1+ ions.
equation to find moles from conc and volume
mol = conc x volume
hydrogen bonding
- only occurs with a hydrogen bonded to O,N or F
- this is because they are extremely electronegative
Plum Pudding model
JJ Thompson - 1897
4 bonding pairs
1 lone pair
see saw (102)
enthalpy change of formation
enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions
Exothermic examples
Combustion of methane
oxidation of carbohydrates
Electrospray
Dissolved in volatile solvent, pushed through a charged hypodermic needle. Gains a H+ ion and turned to gas.
larger number of moles = _____ entropy
higher
bond disassociation enthalpy
enthalpy change when all the bonds of the same type in one mole of gaseous molecules are broken
How does distance affect ionisation energy
An electron closer to the nucleus has a much stronger attraction.
4 bonding pairs
0 lone pairs
tetrahedral (109.5)
Ammonium ion
NH4 +
Factors affecting ionisation energy
Nuclear charge
Distance from nucleus
Shielding
steps to make a standard solution
1- calculate number of moles required
2 - calculate grams required from this
3 - place weighing boat on balance and weigh this mass. Tip into beaker and reweigh the boat. Subtract to find precise amount used.
4 - add distilled water and stir
5 - tip to volumetric flask using funnel.
6 - rinse the beaker and top flask to required volume.
enthalpy change of hydration
enthalpy change when 1 mole of aqueous ions is formed from 1 mole of gaseous ions
dative bond definition
both electrons in a covalent bond come from one atom
hess’ law
the total enthalpy change of a reaction is independent of the route taken
Chromium electronic structure
1s2 2s2 2p6 3s2 3p6 3d5 4s1
second electron affinity
enthalpy change when 1 mole of gaseous 2- ions is formed from 1 mole of gaseous 1- ions.
formula to calculate enthalpy change
q = mc <>T
enthalpy change = mass of water x SHC x change in temp
what must delta G be equal to or less than for a reaction to be feasible
0
method for calorimetry of a neutralisation reaction
- add a known volume of acid to an insulated container and measure temperature
- add a known volume of alkali and record temperature at regular intervals
- find temperature change
properties of metals
- high melting point (due to strong electrostatic attraction)
- more delocalised electrons, the stronger the bond
- delocalised can pass energy, so good conductors
is bond breaking exo or endo
endothermic, since energy is required
define ionic bonding
when one or more electrons are transferred from one atom to another
Van der waal forces
- present in all atoms and molecules
- electrons in charge clouds move constantly, leading to a temporary dipole.
- this induces a dipole in a neighboring atom
Standard enthalpy of formation
enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions
Endothermic definition
energy is absorbed
graphite structure
sheets of hexagons bonded with weak VDW forces with delocalised electrons
equation to find mol from mass and mr
mol = mass / mr
2 bonding pairs
2 lone pairs
bent (104.5)
factors affecting the strength of VDW forces
- size (mr) of molecule
- shape of molecule (the closer the molecules, the stronger the forces
endothermic examples
thermal decomposition of calcium carbonate
photosynthesis
Bohr model
Bohr
electrode equations in a hydrogen oxygen fuel cell
Positive = O2 + 2H2O + 4e- = 4OH-
Negative = 2H2 + 4OH- = 4H2O + 4e-
highest to lowest entropy (solid liquid and gas)
Highest - gas
Lowest - solid
hydroxide ion
OH -
stages of mass spec
1) Ionisation
2) Acceleration
3) Ion drift
4) Detection
6 bonding pairs
0 lone pairs
octahedral (90)
define molecules
when two or more atoms bond together using covalent bonds
equation to find particles from mol and avogadro’s constant
particles = moles x av const
Rutherfords observations
Alpha particles deflected at large angles - all positive charge is in centre
Most passed through - most of atom is empty space
empirical vs molecular formulas
Empirical - simplest whole number ratio
Molecular - the actual numbers in a compound
atom economy
(mr of desired products / mr of all reactants ) x 100
metallic structure
- giant metallic lattice
- outermost shell is delocalised (free to move)
- positive ions are attracted to these electrons
How many particles does one mol contain
6.02 x 10^23
What did JJ Thompson discover
Electron
Percentage yield
(actual yield / theoretical yield) x 100
define le chatelier’s principle
if a reaction at equilibrium is subjected to a change in concentration, pressure or temperature, the position of equilibrium will move to counteract the change.
collision theory
- particles in liquids and gases are constantly moving and colliding with each other.
- in order for a reaction to occur, the particles must collide in the right direction and with a certain minimum amount of energy
define dipole
a difference in charge between two atoms due to a shift in electron density in the bond
define compound
when different elements bond or join together
Behaviour of ionic compounds
- Conductive when molten / dissolved but not when solid
- High melting points
- tend to dissolve in water
