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Created by

Tom Prior

Cards (80)

How do you calculate the RAM?
You do the percentage abundance* Mr
How do you determine RAM using instrumental methods?
Mass spectrometer
Place sample in spectrometer
vaporised an ionised into +ive ion
It is then accelerated
the heavier ions are slower and vice versa
they are then put on an m/z graph the greater the abundance the greater the signal
What is the relative atomic mass?
Weighted mean mass of an atom relative to 1/12th the mass of an atom of carbon-12
What is relative isotopic mass? 
It is the mass of an isotope relative to 1/12th of the mass of a carbon-12
What does the 𝛿 symbol represent?
Partial charge with 𝛿+ being a slightly positive and 𝛿- being a slightly negative charge
What is a polar bond?
It is a bond where an electron pair is shared unequally between the bonded atoms, it is polar when they have differing electronegativity values resulting in polar covalent bonds
What is a pure covalent bond? 
It is where a covalent bond is between two of the same element so electron pairs are shared equally
What is a non-polar bond? 
It is where there is no or little difference in electronegativity, with the electrons being shared equally between each element
How is electronegativity measured?
It is measured using the pauling scale which depend on the positions in the periodic table.
Electronegativity trends on the periodic table?
It increases as you move right and upwards
What is electronegativity? 
It is the ability of an atom to attract the bonding electrons in a covalent bond
Why do some molecules take the shapes that they take?
Electron pairs repel eachother as far apart as possible and take an arrangement of structures. Lone pairs repel more than bonding pairs
What is the electron repulsion theory? 
It is a model that will predict shapes of molecules, electron pairs surrounding the central atom determine the molecule or ion
The pairs repel one another so they are as far apart as possible, minimising repulsion and maintaining a shape
Differing numbers of electron pairs will have differing shapes
How is bond enthalpy linked to covalent bonding?
It serves as a measurement of the covalent bond strength, the larger the enthalpy the stronger the covalent bond is
What is a dative covalent bond?
It is a covalent bond in which the shared pair of electrons has been supplied by the bonding atom only. (it has basically bonded onto a lone pair)
What is covalent bonding?
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the atom. It occurs between two non metals
Why is it important to not only consider atom economy for a reaction?
Some reactions may have high atom economies but may use rare minerals so might not be affordable
Some reactants might not have high % yields in comparison to atom economies meaning it might not be viable
How do you calculate atom economy?
It is the sum of molar mass of desired products/sum of all molar mass of all products * 100
Why are reactions with high atom economies desireable?
It means there is a large proportion of desired products and few unwanted waste products
It is important for sustainability as it makes the best of natural resources
What is a limiting reactant?
It is a reactant that will be used up before the other reactants and so will stop the reaction,
Why might percentage yield be less than 100 percent?
Reaction may not have gone to completion
Other reactions might have taken place
Purification may have resulted in a loss of a producy
Percentage yield calculation? 
actual yield/theoretical yield *100
Ideal gas equation? 
PV = nRT
P- Pressure (pa)
V- Volume (cm3/dm3)
n- moles
R- Ideal gas constant 8.31
T- temperature in kelvin
How to convert from celcius to Kelvin?
+273
What are the conditions needed for the ideal gas equation?
Random motion
Elastic collisions
Negligible size
No inter molecular forces
Moles (volume)? 
mol= Volume/24
Moles (concentration calculations)? 
moles= conc*volume
needs to be in dm3
How to dehydrate a salt?
Heat in a crucible and allow all the water molecules to evaporate
This will leave an anhydrous salt behind which changes from blue to white in colour
What is a hydrated salt?
It is a salt which has water as part of its crystalline structure
What is the empirical formulae?
It is the simplest whole number ratio of each element in a compound
What is the molecular formula? 
It is the number of atoms of each element in a molecule
Moles? 
m= Mass/Mr
What is a mole? 
It is the amount of a substance which contains 6x10^23 particles in it
What are intermolecular forces? 
They are weak interactions between the dipoles of different molecules, there are 3 categories: Induced dipole dipole, permanent dipole dipole and hydrogen bonding. They are largely responsible for physical properties such as MP and BP
What are london forces?
Weak intermolecular forces that exist between all molecules, they act between induced dipoles in different molecules
What is the origin of dipoles?
Movement of electrons results in a changing dipole
At any instant a dipole will exist but it is constantly changing
The instantaneous dipole induces a dipole on a neighbouring molecule
This induces dipoles on further molecules etc
What does the strength of a london force depend on?
Electrons in the molecule
The strength of the instantaneous and induced dipole
Number of protons
The attractive force between molecules
What is a permanent dipole dipole interaction? 
They are interactions that act between permanent dipoles in different polar molecules
What is a simple molecular substance?
A substance made up of simple molecules, with small units containing definite numbers of atoms
In a lattice it will have weak intermolecular forces
And be bonded together strongly by covalent bonds
Properties of simple molecular substances?
All have covalent bonding
Low MP and BP
Not conductors of electricity as there is no mobile charged particles