Year 1 - A level Flashcards
What are the 5 stages of mass spectroscopy
1-Vapourise sample 2-Ionisation(remove an electron) 3-Acceleration(using electric field) 4-Deflection(using magnetic field) 5-Detection
Ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms
What is an orbital?
Area of space which can hold a maximum of 2 electrons
How many electrons can be held in s, p and d subshells?
S - 1 orbital - 2e
P - 3 orbitals - 6e
D - 5 orbitals - 10e
What is the order of the first 5 shells?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d
What is relative atomic mass?
The abundance of an elements isotopes using percentage to calculate an average atomic mass against a carbon 12 atom
What is an isotope?
Atoms with the same number of protons and different number of neutrons.
What effects ionisation energy?
- Electron shielding, further subshell lower I.E.
- No. protons, more protons higher I.E.
- Electron repulsion
How does I.E. change generally: -down a group, -across a period
Down group: 1st I.E. decreases as more shielding
Across period: Increases as more protons.
-Mg –> Al decrease since Al e coming from a higher subshell
-P –> S decrease as S electron is paired = more repulsion
Oxidation number for: Element, fluorine, hydrogen and oxygen(not with F or H)
element = 0 Fluorine = -1 Hydrogen = +1 Oxygen = -2
Steps to making 1/2 ionic equations?
- Balance all but H and O
- Add H2O to balance O
- Add H+ to balance H
- Add e- to balance charge
- Check with oxidation states
What is the reaction between Cl2 and a cold and hot alkali(e.g. NaOH)?
COLD: Cl2 + 2NaOH --> NaCl + H2O + NaOCl -Cl2 is reduced and oxidised called: Disproportionation reaction HOT: 3Cl2 + 6NaOH --> 5NaCl + NaClO3 + 3H2O
What is ΔH⦵?
Change in enthalpy
What is enthalpy?
Energy per mole
What does ⦵ mean?
Standard conditions, 100kPa and 298K
What does it mean when ΔH⦵ is negative or positive?
Negative = exothermic, surroundings gain heat Positive = endothermic, surroundings get colder
What is Q = mcΔT
Energy of surroundings = mass of surroundings x specific heat capacity x temp. change.
(In Joules)
What does energy change of system =?
Energy change of system = - energy change of surroundings
ΔH =?
ΔH = energy change of system / moles
Definition of bond energy?
Amount of energy required to break ‘1 mole of a particular bond’ for gaseous atom
Why aren’t bond energies correct?
They are averages
Define ΔH⦵c? Enthalpy of combustion
Enthalpy change when 1 mole of a substance is burnt in excess O2 under standard conditions
What are all the diatomic elements?
B,O,C,I,H,N,F(Becasue Of Chem I Have No Friends)
Define ΔH⦵f? Enthalpy of formation
Enthalpy change when 1 mole of a compound is formed from it’s elements, in their STANDARD STATES under standard conditions
ΔH⦵n? Enthalpy of neutralisation
Energy change when ‘1 MOLE OF WATER’ is formedin reduction between acid + base, under standard conditions
What are the 3 types of Hess Cycle?
- Given ΔH⦵c to work out ΔH⦵f
- Given ΔH⦵f to work out ΔH⦵ decomposition
- Work out ΔH⦵ solution
ΔH⦵ solution?
Difference between lattice energy and hydration energy
What is lattice energy?
Energy required to form 1 mole of ionic solid from gaseous ions, under standard states
What affects distortion(how good it is at polarising) in +ve ion?
-Small radius and high charge means best at polarising.
More distortion means furthest from ionic model and bigger gap between experimental and theoretical lattic enthalpies
What affects how the -ve ion is distorted?
-Close to 0 charge + big radius means easy to distort.
What is Entropy(S)
The number of ways of organising particles in a substance. Measured in JK-1mol-1?
- Many ways(gas) = high entropy
- Few ways(solid) = low entropy
ΔS =
ΔS = S products - S reactants
ΔG =
ΔG = ΔH - TΔS sys - change Δs by /1000
If -ve then spontaneous
Measured in KjMol-1
ΔS total =
Therefore ΔSsurr =
ΔS total = ΔS sys - ΔH/T - change ΔH x1000 for KJ to J
If +ve then spontaneous
Measured in JK-1Mol-1
ΔSsurr = -ΔH/T
What is the ideal gas equation?
pV = nRT
What are the three main gas laws?
- Boyle’s law
- Charles’ law
- Avagadro’s principle
What is Boyle’s law?
- Volume of a fixed mass of gas is inversely proportional to it’s pressure
- V ∝ 1/p
What is Charles’ law?
- The volume of a fixed mass of gas is directly proportional to its thermodynamic temperature
- V ∝ T
What is Avagadro’s principle?
- Equal volumes of different gases at the same temperature and pressure contain the same No. of molecules
- V ∝ n
What are features of an ideal gas?
- No IMF’s
- The kinetics theory explains how their molecules act
- All collisions are perfectly ‘elastic’
- The molecules of an ideal gas have no size (they occupy zero volume)
What are isoelectric ions?
Ions that have the same number of electrons of same electronic configuration. E.g. Li+ and He
How does ionic radius change: -down group, -across period?
- Down group it gets larger as more shells
- Across period it gets smaller as more protons E.g. N3- –> Al+
Properties of ionic compounds? M.P. and strength
Melting point is very high as a large amount of energy is needed to overcome electrostatic attractions.
Strength is brittle as any dislocation causes the layers moving and similar ions repel each other.
How do ionic substances dissolve?
The negative oxygen in water attracts to positive crystal ion.
Positive hydrogen in water attracts to negative crystal ion.
What is the octet rule?
The tendency for an atom to acquire a noble gas configuration.
As a general rule, atoms share electrons to get the nearest noble gas configuration.
How is bond length and strength linked?
The larger the atom the longer the bond and therefore weaker.
What is a dative covalent bond?
A shared pair of electrons which has been provided by one of the bonding atoms only. Also called co-ordinate bond.
What is a sigma bond?
A bond where the line of electron density is concentrated symmetrically along the line connecting the two atoms.
Can be formed with 2 S orbitals or an S and a P or 2 P orbitals end to end
What is a pi bond?
Both P orbitals overlapping side by side so a bond is formed above and below the nucleus.(forms one pi bond)
What is hybridisation?
When an S and a P orbital produce new orbitals called sp orbitals.
These are called hybrid orbitals, this means is that both the s and one p orbital are involved in bonding to the connecting atoms.
What are the five allotropes of carbon and a use for each?
Graphine: -2d, very strong Nano-tube: -Used for injections Buckminsterfullerene: -60 carbons in hexagons and pentagons Diamond: -Drill bits Graphite: -Lubricants
Which bond in more repulsive, lone pair or bonding pair?
LP LP > LP BP > BP BP
With lone pair lone pair most repulsive
What is the Valence shell electron pair repulsion theory?(VESPR)
The ability to predict a simple molecule’s shape due to the ideas that electrons repel and will therefore, sit as far from each other as possible
What scale measures electronegativity?
The Pauling scale
What is electronegativity?
The ability of an atom IN A MOLECULE to attract electrons to itself.
What are the electronegativity trends in the periodic table?
-Decreases down group, increases across period
This is because more shells means more repulsion and more protons means more attraction.
What is the difference between non-polar and polar bonds in terms of electronegativity?
- Non-polar(covalent): Have similar atoms with similar electronegativity
- Polar(ionic): One side will have delta -(negative side) and one delta +(positive side) Dipole formed and bond is said to be polar.
What does greater electronegativity difference mean?
Greater polarity = more ionic
What does polarisation do to bonding?
It distorts ionic bonds to give them covalent characteristics. Also distorts electron-cloud.
What affects how an anion or cation is polarised/polarises?
Anions with charge close to 0 or larger radius are more easily polarised.
Cations with a smaller radius or greater charge have a greater ability to polarise anion.
What are the two categories of bonds and what bonds are in them?
Chemical(Intramolecular): Covalent, Ionic, Metallic, dative covalent
Physical(Intermolecular): London forces, dipole-dipole interaction, hydrogen.
What are london (dispersion) foces?
Intermolecular forces between molecules. Moving electrons group instantaneously on one side to create instantaneous charge forming temporary dipole
What are dipole-dipole interactions?
Between molecules with polar bonds working with London forces meaning more energy needed to separate molecules. Creates higher M.P than expected for mass.
What is hydrogen bonding?
In molecules containing hydrogen bonded to N, O or F. Increases B.p.
Give 5 facts about group II elements?
Metal, Good conductivity, grey solids, Oxidation state of 2+, Form basic oxides and basic hydroxides. Less reactive than group I but, more dense and high M.P.
What colours are flame tests for group II ions?
SR2+ = Crimson Ca2+ = Brick red Ba2+ = Apple green Mg2+ = White Electrons jump back down energy levels and energy is given out as light
Solubility and PH in group II hydroxides?
More soluble down group as ionic bonds weaker. Therefore, more OH- ions makes solution more alkaline
What is disproportionation? Happens with halogens
Simultaneous oxidation and reduction of a single species during a chemical reaction.
Change in energy for bonds breaking?
Energy taken in - endothermic
Change in energy for bonds formed?
Energy released - exothermic
What is the definition of rate?
The change in concentration of a reactant of product per unit time.
On a concentration time graph how do you find rate? Hence what formula gives rate?
Rate = gradient. = concentration/time
What 5 factors increase rate? And why
- Higher concentration
- Higher temperature
- Larger Sa:V = small pieces
- Higher pressure
- Using catalyst.
On concentration time graphs, how do you know the order?
Zero order = straight
First order = constant half life
Second order = Half life increases with time
What are the two types of catalysts?
Heterogeneous = catalyst and reactants in same phase (state). Homogeneous = catalyst and reactants in different phases (states).
What is the definition of activation energy?
The energy a colliding molecule must possess before a collision will result in a reaction.
What are the axis on a Maxwell-Boltzmann distribution graph?
Fraction of molecules on Y. Energy on X
What does the addition of a catalyst do to a Maxwell-Boltzmann distribution graph?
Shits the Ea line to the left. More molecules with sufficient energy to react.
Name an economic benefit of a catalyst?
- Not much needed to catalyse large amount of reactants.
- Lowered energy demands = less environmental impact due to less CO2 = less production costs.
What do the letters stand for in the rate equation, Rate = k[A]^m[B]^n?
k = rate constant.
A and B are reactants.
m and n are their orders.
What does order tell you?
How concentration of reactants affects rate.
What is the rate determining step (R.D.S)?
The slowest step which determines overall rate. Any step which appears after it will not be in rate equation.
What is an intermediate?
A species formed in one step of a multi-step reaction which is not seen as a reactant or product in the overall equation.
What is the Arrhenius equation?
k = A e^(-Ea/RT) k= rate constant A= frequency factor e= maths e Ea= activation energy R= gas constant = 8.314 JK-1mol-1 T= Temp. in K
How do you rearrange the Arrhenius equation for a graph?
ln k = -Ea/R x (1/T) + ln A y = ln k x = 1/T Grad = -Ea/R y intercept = ln A
Definition of a base?
Hydrogen accepter
When should you talk about electronegativity?
With covalent molecules
Mass of electrons, neutrons and protons?
0.0005, 1 and 1 in u(atomic mass unit)
What is on the x axis and y axis for mass spectroscopy?
x axis: mass/charge aka m/z
y axis:%
What does emission spectra prove?
Evidence of shells
What is VESPR?
Valence shell electron pair repulsion
Why does H20 have a higher boiling point than HF which is higher than NH3?
It has the ‘perfect’ number of lone pairs to hydrogen meaning it can maximise hydrogen bonding.
NH3 has too few lone pairs.
What does hydrogen bonding change?
Higher bp than expected for size of molecule.
H20 less dense than water as hydrogen bonds go stiff.
What is the difference in bp for straight vs brached carbon chains?
Straight have higher as fit more compactly meaning better imf attraction as larger surface area.
What is difference between alkanes than alcohols bp with similar number of electrons?
Alcohols have higher bp as hydrogen bond.
What are the trends in hydrogen halide bp?
HF highest due to hydrogen bonding.
HCl, HBr, HI increasing in that order due to increasing number of electrons and increasing london forces
What type of compound structures are there?
Giant ionic lattice, simple covalent molecule, giant covalent lattice, giant metallic lattice.
What are the different bond types depending on difference in electronegativity?
Zero: Covalent
Low: Polar covalent
High: ionic
What is the atom economy equation?
% atom economy = molar mass of useful product / total molar mass of starting reactants x 100
