A mole of a substance is the amount of that substance that contains the same number of elementary particles as there are carbon atoms in 12 grams of carbon-12
The number of particles in one mole of a substance is 6.02 x 10^23, this is known as Avogadro's number/constant a.k.a. 'L'
Number of particles = number of moles x L
The mass of one mole of a substance is known as its molar mass (gmol^-1)
Mass = Mr x n
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Reacting Masses & Atom Economy
When reactings masses the total combined mass of the reactants must be the same as the total combined mass of the products
The ratio in which species react corresponds to the number of moles, and not their mass
Percentage yield = (amount of product formed/maximum amount of product possible)/100
The atom economy of a reaction is the percentage of the total mass of reactants that can be converted into the desired product
Percentage atom economy = (mass of desired product/total mass of product) x 100
The higher atom economy the more efficient the product process
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Solutions
A solution is a homogeneous mixture of two or more substances in which the proportions of the subtances are indentical throughout the mixture
The major component of a solution is called the solvent and the minor components are called solutes
Water is normally the solvent
The amount of solute present in a fixed quantity of solvent is called the concentration
Number of moles = (volume x concentration)/1000
The procedure by which reacting volumes are determined is known as a titration
In titrations a solution whose concentration is unknown is titrated against a solution whose concentration is known
The solution of the known concentration goes in the burette, whilst the unknown goes in the conical flask
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Gases
PV = nRT
P is the pressure measured in pascals
V is the volume in m^3 (1m^3 = 1000dm^3 = 10^6cm^3)
T is the temperature measured in Kelvin (0 degrees celcius = 273 K)
R is the molar gas constant and is always given (8.31 Jmol^-1K^-1)
PV = mRT/Mr
The density of a gas, or mass/volume, is (m/V) = MrP/RT
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Using Moles
n = PV/RT
n = CV
n = mass/RMM
n = particles/L
Percentage purity = (mass substance would have if pure/mass of impure substance) x 100
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Empirical & Molecular Formula
The empirical formula shows the simplest whole-number ratio in which the atoms in that compound exist
The molecular formula shows the number of each type of atom in the one molecule of that subtance
Finding the empirical formula
Find the mole ratio by dividing the percentage amount of each substance in the compound by its mass number e.g. carbon is 85.8% of the substance, hydrogen is 14.2%, C = 85.9/12, H = 14.2/1
Then divide this by the smallest mole ratio found in order to find the empirical formula e.g. C = 7.15/7.15, H = 14.2/7.15, CH2
Finding percentage composition
Find the relative molecular mass of the given compound e.g. C2H4O2 = 60
Multiply the mass of each substance by the amount of moles of it in the compound e.g. C = 12 x 2
Divide by the RMM e.g. 24/60
Multiply by 100 to get a percentage e.g. 0.4 x 100
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Formulae Of Ionic Compounds
An ion is a species in which the number of electrons is not equal to the number of protons
Positive ions are known as cations
Negative ions are known as anions
Compounds made up of ions are known as salts
Salts have no charge therefore all contain at least one cation and one anion
Ions that remain aqueous before and after the reaction are spectator ions
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