AS physical Flashcards
Atomic structure, amount of substance, bonding, energetics, kinetics, equilibria, redox
What is the formula for the number of electrons in each shell
2n^2 where n is the number of the shell
Explain the process of TOF Mass spectrometry (6 steps)
System is put into a vacuum to avoid collisions with air
Sample is ionised by dissolving in volatile solvent and passing through high voltage needle
Positive ions accelerated to negative plate according to their size and charge
Ions form a beam and travel through flight tube
Ions detected as positive ions pick up electrons and cause current to flow
Data is sent to a computer to be analysed
What is m/z ratio equivalent to for singly charged ion
mass number
Give two uses of mass spectrometry
identifying substances on crime scene (eg. drugs)
identifying elements on different planets
What do the SPDF shapes represent
volume of space where there is a 95% chance of finding an electron
state the order of electron orbitals up until 5p
1s,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p
explain the trend in ionisation energy across a period
increases due to increasing nuclear charge with no added shielding. For group 3 and 6, it can decrease as the new electron operates in a higher sub-orbital, so less energy is required to remove it.
Define the avagadro constant
the number of atoms in 12g of carbon 12
units for volume in PV=nRT
m^3
define empirical formula
the formula that represents the simplest whole number ratio of the atoms of each element present in a compound
Define molecular formula
the actual number of atoms of each element in one molecule of a compound
what is atom economy
mass of desired product/ mass of reactants
name 3 properties of ionic compounds
high melting temperatures
conduct electricity in molten/ aqueous state
brittle
explain why ionic lattices are brittle
a shift in the plane of atoms causes ions of the same charge to contact. These then repel, causing the compound to shatter
give two properties of molecular structures
low melting/ boiling points
poor conductors of electricity
Explain coordinate bonding
An atom with a lone pair donates the lone pair to an electron-deficient atom. Ie. All of the electrons in the shared pair come from one atom
Give 4 properties of metals
conductors of electricity and heat
strong
malleable and ductile
high melting points
What two things determine the strength of a metal
charge of ion
size of ion
Define electronegativity
the power of an atom to attract the electron density in a covalent bond towards itself
Define polarity
the unequal sharing of the electrons between atoms that are bonded together covalently
Give two pieces of evidence for van de Waals forces
boiling points of noble gases increase down the group
boiling points of hydrocarbons increase with increasing chain length
Give the piece of evidence for hydrogen bonding
higher boiling points for hydrides of the NOF elements
Explain why ice is less dense than water
the hydrogen bonds no longer break, so keep the water molecules a fixed distance apart. To fit this structure, the molecules are further apart
bond angle and shape of a molecule with four electron pairs (eg. CH4)
tetrahedron, 109.5
bond angle and shape of a molecule with 5 electron pairs
trigonal bypyramidal, 120 and 90
bond angle and shape of a molecule with 6 electron pairs
octahedral, 90
bond angle and shape of a molecules with 3 bonding pairs and 1 lone pair
triangular pryamid, 107
bond angle and shape of a molecule with 2 bonding pairs and 2 lone pairs
v-shape, 104.5
bond angle and shape of a molecule with 4 bonding pairs and 2 lone pairs
square planar, 90
Describe the structure of diamonds
each carbon covalently bonded to four other carbon atoms, in giant 3d structure
describe the structure of graphite
each carbon atom covalently bonded to three other carbon atoms in 2d structure. These 2d layers are connected by van de Waals forces
Explain the structure of buckminsterfullerene
60 carbon atoms, each bonded to three other carbon atoms, and arranged in a football-like shape
give four uses of thermochemistry
measure energy values used for fuels
calculate energy for different industrial processes
theoretical energy to break bonds, energy released when bonds are made
predicts the feasibility of a reaction
give three ways in which a flame calorimeter is made more efficient
spiral chimney made of copper
flame is enclosed
fuel burns in pure oxygen
Give 5 things that affect rate of reaction
temperature
concentration
pressure
surface area
catalysts
what is the name of the state of the intermediate species at the top of an enthalpy diagram
transition state
How does a catalyst affect rate of reaction
provides an alternative energy pathway with a lower activation energy
What do catalytic converters do
reduce the amounts of polluting gases by catalysing reactions that remove nitrogen oxides, unburned hydrocarbons and carbon monoxides
define adsorption
reactants forming weak bonds with the catalyst surface
define desorption
products breaking away from the surface of a catalyst
Define dynamic equilibrium
a situation in which the composition of a constant concentration reaction mixture does not change because the forward reaction and backward reaction happen at the same rate
state the condition for equilibrium to be reached
closed system
Explain how we know when an equilibrium has been reached
macroscopic properties are constant
eg. density, concentration, colour, pressure
State Le Chatelier’s principle
If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance.
What do catalysts affect concerning equilibrium
the rate at which an equilibrium is reached
What is the catalyst for the haber process
iron
four reasons that a low temperature, high pressure and excess steam cannot be met in an industrial situation for the production of ethanol from hydration of ethene
high pressure causes polymerisation
building and maintenance costs for high pressure systems
low temperature affects rate of reaction
steam dilutes the catalyst
What catalyst is used for production of ethanol from hydration of ethene
phosphoric acid
give the equation for the Kc expression
Kc=[products]/ [reactants]
What affects the Kc expression
temperature
If Kc > 1 where is equilibrium
to the right
For an exothermic reaction, what is the effect of increasing temperature on Kc
Kc
define reducing agent
electron donor
define oxidation states
the number of electrons lost or gained by an atom in a compound compared to the uncombined atom.
Oxidation state of hydrogen
+1 except metal hydrides where it is -1
Oxidation states of group 1, group 2 and Alumininium respectively
always +1,+2,+3
oxidation state of Oxygen
-2 except peroxides (-1) and OF2 (+2)
oxidation state of fluorine
always -1
oxidation state of chlorine
-1 except compounds with Fluorine or Oxygen where it has positive values
What is the rule for which atoms have negative oxidation numbers
the most electronegative atom has a negative oxidation state
