AS Chemistry OCR F321 revision notes

AS Chemistry OCR F321 revision notes - dunno how useful these are...

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Chemistry
UNIT 1 ATOMS, BONDS AND GROUPS (F321)
Atoms
Isotopes = atoms of the same element with different numbers of neutrons
Relative isotopic mass = mass of an atom of an isotope compared with onetwelfth of the mass
of an atom of carbon12
Relative atomic mass = weighted mean mass of an atom of an element compared with
onetwelfth of the mass of tan atom of carbon12
Relative molecular mass = weighted mean mass of a molecules compared with onetwelfth of
the mass of an atom of carbon12.
Molar mass = is the mass per mole of a substance
n=m/M (n = amount of substance, mol m=mass, g M=molar mass, g/mol)
Empirical formula = the simplest wholenumber ratio of atoms of each element present in a
compound
Molecular formula = the actual number of atoms of each element in a molecule
GAS
Molar volume = volume per mole of gas, approx. 24.0 dm3 mol1 at RTP
If volume in dm3, n=V/24
If volume in cm3, n=V/24000
SOLUTION
Concentration = the amount of solute, in mol, dissolved per 1dm3 of solution
n=c x V(in dm3)
Standard solution = a solution of known concentration
used in titrations
Concentrated a large amount of solute per dm3
Dilute small amount of solute per dm3
Chemical equations
Acids
Sulfuric acid > H2SO4
Hydrochloric acid > HCl
Nitric acid > HNO3

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Ethanoic (acetic) acid > CH3COOH
Methanoic (formic) acid > HCOOH
Citric acid > C6H8O7
Acid is a proton donor (releases H+ ions)
Bases
Metal oxides and hydroxides (e.g. CuO and Mg (OH)2 )
Ammonia and amines (e.g.…read more

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Roman numeral
Redox reactions
oxidation = loss of electrons or increase in oxidation number
reduction = gain of electrons or decrease in oxidation number
OILRIG
Ionisation energy
First ionisation energy = the energy required to remove on electron from each atom in one mole
of gaseous atoms to form one mole of gaseous 1+ ions
affected by:
1 atomic radius greater radius, smaller the attraction
2 nuclear charge greater charge, greater attractive force
3 electron shielding more inner shells, smaller attraction
Successive ionisation energies =…read more

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Ionic bonding
Ionic bonding = electrostatic attraction between oppositely charged ions
DOT AND CROSS DIAGRAMS
Group 1,2,3 have positive charge same as group number
Group 4 usually no charge
Group 5,6,7 have negative charge
NO3 , CO3 2, SO4 2, NH4 +
properties
soluble in POLAR solvents (e.g.…read more

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Electronegativity
Electronegativity is measure of attraction of bonded atom for pair of electrons in covalent bond
more electronegative atom (greater attraction) takes negative charge electronegativity
increases to the right of P.T.…read more

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MO)
react with water, product = hydroxide (M(OH)2) and hydrogen gas
Reactions
MO and M(OH)2 both react with acids to form a salt and water
Observe > solid dissolves
Oxides react with water to form metal hydroxide
Hydroxides react with water to form alkaline solutions
Ca(OH)2 (s) + aq > Ca2+ (aq) + 2OH (aq)
Solubility of hydroxides in water increases down group, more alkaline solutions produced
carbonates decomposed by heat THERMAL DECOMPOSITION
MgCO3 (s) > MgO (s) + CO2 (g)
more difficult to decompose…read more

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Form solutions with different colours
Chlorine oxidises Br and I ions:
Cl2 (aq) + 2Br (aq) > 2Cl (aq) + Br2 (aq) orange in water, orange in cyclohexane
Cl2 (aq) + 2I (aq) > 2Cl (aq) + I2 (aq) brown in water, purple in cyclohexane
Chlorine is reduced. Bromine or iodine is oxidised.…read more

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