Core Definitions and Core Knowledge - AS level Flashcards
Periodicity def
A repeated pattern or trend
Relative Atomic mass def
The relative atomic mass of an element is the average mass of its atoms, compared to 1/12th the mass of a carbon-12 atom
General formula def
formula for a family of compounds. E.g. alkanes‡ CnH2n+2 where n is the number of carbon atoms
Empirical formula def
shows the ratio of atoms in a compound. It is the simplest ratio in which atoms combine to form a compound
Molecular formula def
tells us how many of each type of atom there are in each molecule of the compound
Skeletal formula def
all the hydrogen atoms are removed from carbon chains, leaving just a carbon skeleton with functional groups attached to it
Displayed formula def
shows all the bonds in the molecule as individual lines (each line represents a pair of shared electrons)
Structural formula def
shows how the various atoms are bonded
Hydrated
A crystalline compound containing water molecules
Anhydrous def
A substance containing no water molecules
Water of crystallisation def
The water molecules bonded into a crystalline structure of a compound
How to improve results of water of crystallisation experiment
- Use a mass balance that calculates to a greater number of decimal places to get a more accurate mass reading
- Heat mixture until you record a constant mass
What happens if compound in water of crystallisation decomposes further?
How to stop this?
- Anhydrous solid mass at end will be less than it should be
- You could heat it more gently, or take mixture off of heat
First ionisation energy
The energy required to remove one electron from each atom in one mole of gaseous atoms to produce one mole gaseous 1+ ions
Second ionisation energy
The energy required to remove one electron from each 1+ ion in one mole of gaseous 1+ ions to produce one mole of gaseous 2+ ions
Atomic number def
Number of protons in the nucleus
Orbital def
A region within an atom that can hold up to two electrons with opposite spin
What is meant by one mole of substance?
- As many particles as there are carbon atoms in 12g of carbon - 12
- Or: 6.02x10^23 atoms
How do London Forces arise?
-there is an uneven distribution of electrons present in molecule
↳ this creates an instantaneous dipole
-these cause induced dipoles in neighbouring molecules
Trend in boiling points of chlorine, bromine and iodine
H
Oxidising agent def
A substance that oxidises another substance by attracting its electrons and becoming reduced in the reaction itself(absorbs electrons from other substances)
Reducing agent def
A substance that reduces another substance in a reaction but becomes oxidised in the reaction itself(loses electrons, donates them)
Metallic bonding def
The electrostatic attraction between between cations and delocalised electrons
Covalent bonding def
The electrostatic attraction between two atomic nuclei and a shared pair of electrons
Ionic bonding def
The electrostatic attraction between oppositely charged ions
Electronegativity def
The ability of an atom to attract a lone pair of electrons
Anomalous properties of water
- Adhesion/Surface Tension
- Cohesion
- Ice is less dense than water - water molecules are more spread apart by hydrogen bonds
- High specific heat capacity
- High latent heat of vaporisation
Radical definition
A species or element with an unpaired electron
What is meant by fractional distillation?
The separation of different hydrocarbons from crude oil by distillation due to different boiling points of each fraction
Methods for reducing pollution due to plastic/polymer disposal
- Make photodegradable polymers
- Make biodegradable polymers
- Combustion of the polymers to produce energy
- Melt, reshape and remould the polymers for reuse
- Used in feedstock for plastics and chemicals
- Use waste polymers in organic feedstock
- Use waste polymers in cracking
Atom economy def
(sum of) the molecular masses of the desired product ÷ sum of molecular masses of all reactants x 100 to get a percentage
Alkali def
A substance that releases OH- ions in solution
Acid def
A substance that releases H+ ions in solution
Standard solution def
A solution of known concentration
How to prepare a standard solution
H
Linear shape info
Bond angle: 180 Degrees
2 Bonded Pairs
0 Lone pairs
Non linear shape info
2BP
At least one LP
Bond angle less than 120 Degrees
Trigonal planar shape info
Bond angle: 120 Degrees
3BP
Trigonal bipyramidal shape info
Bond angles: 120 and 90 Degrees
5BP
Tetrahedral shape info
Bond angle: 109.5 Degrees
As long as 4BP and no LP
Octahedral shape info
Bond angle: 90 Degrees
Suggest two reasons why standard enthalpy changes of combustion determined experimentally are less exothermic than the calculated theoretical values.
- Conditions may have been non-standard
- Heat may have been lost to the surroundings
- Incomplete combustion(for standard enthalpy of combustion)
Bond angle of a molecule with 4BP and 0LP
109.5 Degrees
Bond angle of a molecule with 3BP and 1LP
107 Degrees
Bond angle of a molecule with 2BP and 2LP
104.5 Degrees
Standard Enthalpy Change of Formation def
The enthalpy change that takes place when 1 mole of a compound is formed from its
constituent elements.
All products and reactants are in standard states and conditions
Standard enthalpy change of combustion def
The enthalpy chnage that takes place when 1 mole of a compound reacts with oxygen and is completely burnt.
All products and reactants formed under standard conditions in standard states
Standard Enthalpy change of neutralisation def
the enthalpy change associated with the formation of one mole of water from a reaction
standard comditions and states
Standard enthalpy change of reaction def
the enthalpy change associated with a given reaction (in the molar quantities given in the equation)
Average bond enthalpy def
The average enthalpy change that takes place when breaking one mole of a given type of bond in the molecules of a gaseous species, by heterolytic fission,
Are bond enthalpy values positive of negative values?
Always positive
As energy is required/taken in to break the bonds
Why can enthalpy change of formation not be measured directly?
- Byproducts may be formed
- Activation energy is too high
Reflux Def
The continuous boiling and condensing of a reaction mixture to ensure the reaction takes place without boiling dry.
In Markownikoffs rule, explain why one product formed is in much greater quantity than the other organic product.
(2 Marks)
The major product is the most stable carbocation formed
The most stable carbocation is the carbon that is bonded to the most carbon groups/atoms
Identify two potential disadvantages of using catalyst in industrial processes
Catalysts are expensive
Cost - expensive to remove catalysts from reaction mixture and products
Catalysts could be potentially toxic/harmful to humans
