Key point revision notes

The bare minimum you need to know for OCR chemistry salters B for F331.

A summary of all the key points

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  • Created on: 06-06-10 13:18
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Avogadro's constant (L):
6.02 x 1023 particles in 1 mole
Number of moles = number of particles you have
number of particles in a mole
Atoms of the same element with the same atomic number but a different number of neutrons
E.g carbon- 12 and carbon- 14
Relative isotopic mass:
The mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is
12, carbon-14 is 14
Subatomic particle Relative mass Relative charge
Proton 1 +1
Neutron 1 0
Electron 1/2000 -1
Alpha particles Beta particles Gamma rays
What they are Helium nuclei Fast moving electrons Very short EM wave
Penetrating power Stopped by paper Stopped by tin aluminium Stopped by very thick lead
Ionising ability Strong Moderate Weak
Deflection in electric field Slight Large Not deflected
Alpha Decay: 238 234 4
92 90 2
Beta Decay: 14 14 0

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Gamma: No change in atoms, just a release of energy from the nucleus.
Half Life: the time it takes for half the radioactive nuclei in a sample to decay.
The half life is fixed for any given radioisotope and is not affected by temperature.
Iodine -131 has a half life of 8 days. If you start with 24g of the isotope, what mass
remains after 32 days?
1. After 8 days, 12g of the sample remains
2.…read more

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Standard State: 1 atmosphere pressure + 298K (25ºC)
Enthalpy change in combustion: The enthalpy change when 1 mole of a substance burns
completely in oxygen under standard conditions
Enthalpy change of formation: The enthalpy change when 1 mole of a substance is formed from
its constituent elements. Both reactants and products are in standard state.
Bond enthalpy: the average energy required to break the bonds in 1 mole of gaseous compounds
Entropy: a measure of the number of ways in which particles can be arranged.…read more


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