the core principles of chemistry..

Here are unit 1 edexcel notes,,these are not typed by me though,,i won't take the just providing to those who need these notes in EASSSYYY words..

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Work of Hamza (Mathemagician) Unit 1.1
Unit 1.2: Formulae, equations and moles
Learning bit:
Avogadros constant is the number of carbon atoms in exactly 12g of the carbon12
isotope. It is equal to 6.02x 10^23 mol^1.
One mole of a substance is the amount of that substance that contains 6.02x 10^23
particles of that substance. This means that one mole of a substance is its relative atomic or
molecular mass expressed in grams.
The molar mass of a substance is the mass (in grams) of one mole.
Amount of substance is the number of moles of that substance.
The empirical formula is the simplest whole number ratio of the elements in the compound.
Calculation of empirical formulae from percentage data
Easy way of calculating it:
Element % of element %/Ar Divide by lowest
Carbon 48.7 48.7/12 = 4.1 4.1/2.7=1.5
Hydrogen 8.1 8.1/1 = 8.1 8.1 / 2.7 = 3
Oxygen 43.2 43.2 / 16 = 2.7 2.7 / 2.7 = 1
The last column gives the empirical formula, but if any value in this column comes to a
noninteger value, multiply it by 2 or 4 etc
So here, the empirical formula is C3H6O2.
These must balance. The number of atoms of an element on one side of the equation must
be = to the other side
Ionic equations
3 rules:
1. Write the ions separately for solutions of ionic compounds
2. Write full `molecular' formulae for solids and all covalent substances
3. Spectator ions must be cancelled and so do not appear in the final equation.
***they must also balance for charge***

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Work of Hamza (Mathemagician) Unit 1.1
There are 3 ways of calculating the amount of substance (in moles):
1. For pure substance (X)
Amount of X (in moles) = mass of X (in grams)/its molar mass
2. For solutions:
The amount of solute = concentration (in mol dm^3) x volume (in dm^3)
3.…read more

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Work of Hamza (Mathemagician) Unit 1.1
Learny bits:
1. Chemical bonds:
1. Ionic ­ between separate ions
2. Covalent: divided into 2 types
o polar covalent where the bonding pair of electrons is nearer to one atom
o Pure covalent where the bonding pair of electrons is shared equally
o Metallic bonding caused by electrons delocalised throughout the solid
2.…read more

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Work of Hamza (Mathemagician) Unit 1.1
= (Pi) p bond.
o A dative covalent bond is a covalent bond formed when one of the
overlapping orbitals contained 2 electrons, and the other none.
o A metallic bond results from the delocalisation of the outer electrons
amongst all the atoms. It can be regarded as a "sea" of electrons able to
move amongst a regular array of positive metal ions.…read more

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Work of Hamza (Mathemagician) Unit 1.1
o Covalent bonding
These are either:
Giant atomic, such as diamond, graphite and quartz
Simple molecular, such as iodine and many organic molecules
Hydrogenbonded molecular, such as ice and ethanol
Noncrystalline such as polymers
o Effect of heat (melting)
**** It is quite possible that you will be asked something related to this in the
When a solid is heated from room temperature until it melts:
The particles (ions, molecules or atoms) vibrate more.…read more

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Work of Hamza (Mathemagician) Unit 1.1
If the number of electrons in 2 different substances is about equal and neither
has hydrogen bonds, then dipole/dipole forces cause a difference in boiling
temperature. This is the case between butane (34 electrons, nonpolar, boiling
temp = 0.5 deg Celsius) and propanone (32 electrons, but polar, so boiling
temperature + 56.2 deg Celsius).…read more

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Work of Hamza (Mathemagician) Unit 1.1
Melting and boiling temps. Of the period 3 elements (Na to Ar)
The melting temperature depends upon the strength of the forces between
particles that separate during melting (or boiling).
These particles may be:
Metal ions in a sea of electrons in metals
Covalently bonded atoms in a giant atomic structure
Molecules with intermolecular forces between them in simple
molecular solids
***To understand the trends in melting temp.…read more

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Work of Hamza (Mathemagician) Unit 1.1
A reducing agent is a substance that reduces another substance and so is itself
oxidised. The half equation involving a reducing agent has electrons on the
righthand side, i.e it gives electrons to the substance being reduced.
*** remember OIL RIG (Oxidation Is Loss, Reduction Is Gain)***
Oxidation numbers
The oxidation number is the charge on an atom of the element in a compound
calculated assuming that all the atoms in the compound are simple monatomic ions.…read more

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Work of Hamza (Mathemagician) Unit 1.1
e.g. For the overall equation for oxidation of Fe2+ ions by MnO4 ions:
add MnO4 + 8H+ + 5e Mn2+ + 4H2O
to 5 x Fe2+ Fe3+ + e
MnO4 + 8H+ + 5Fe2+ Mn2+ + 4H2O + 5Fe3+
Topic 1.…read more

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Work of Hamza (Mathemagician) Unit 1.1
Ionisation energies
The value of the 1st ionisation energy for Group 1 and of the 1st and 2nd
ionisation energies for Group 2 decreases down the group. This is
because as the atoms gets larger, the outer electrons are further from
the nucleus and so are held on less firmly. The increase in nuclear
charge is compensated for by an increase in the shielding by the
inner electrons.…read more


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