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Summary A level Chemistry amount of substance PDF ANKI flashcards
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Definition of relative atomic mass (Ar) Weighted average mass of an
atom of an element, taking into account its naturally occuring
isotopes, relative to 1/12 of the mass of a cerbon 12 atom
Definition of relative molecular mass (Mr) Mass of a molecule
compared to 1/12 relative atomic mass of a carbon-12 atom (found by
adding up the Ar of all atoms in the molecule)
Avogadro constant definition Number of atoms in 12g of 12C, i.e.
number of entities in a mole<br>6.022 x 10<sup>23</sup>
Moles definition Amount of substance that contains 6.022 x
10<sup>23</sup> particles<br>Applied to electrons, atoms,
molecules, ions, formulas and equations
Number of particles equation Number of particles = no. of moles x
(6.022 x 10<sup>23</sup>)
Moles equation Moles = mass (g) / Mr
Percentage composition by mass equation % composition = (total mass
of element in formula / Mr) x100
Reacting masses moles method 1) Work out no. of moles of formula
given with mass<br>2) Use balanced equation to find no. of moles of
desired product/reactant<br>3) Work out mass of this number of moles
Reacting masses ratios method 1) Work out Ar/Mr of species
concerned<br>2) Multiply values by any big numbers in balanced
equation<br>3) Mass of reactant / (2) for reactant = Mass of
product / (2) for product
Concentration of a solution definition Expressed in terms of number
of moles of solute dissolved in each dm<sup>3</sup> of solution
Concentration equations No. of moles = (volume (cm<sup>3</sup>) /
1000) x concentration (mol dm<sup>-3</sup>)<br><br>Concentration
(mol dm<sup>-3</sup>) = (moles x 1000) / volume (cm<sup>3</
sup>)<br><br>Volume (cm<sup>3</sup>) = (moles x 1000) /
concentration (mol dm<sup>-3</sup>)
Ideal gas equation PV = nRT<br>P = gas pressure, Pa<br>V = gas
volume, m<sup>3</sup> (cm<sup>3</sup> x 10<sup>-6</sup>)
(dm<sup>3</sup> x 10<sup>-3</sup>)<br>n = number of moles<br>R
= gas constant (8.31 JK<sup>-1</sup>mol<sup>-1</sup>)<br>T =
temperature, K (273 + temp in celcius)
What is empirical formula Formula that gives simplest ratio of
atoms of each element in the compound
How to find empirical formula 1) write out mass or % of each
element<br>2) divide each mass or % by Ar of element<br>3) divide
these by the smallest answer. If answers near 1/2s, multiply by 2.
If near 1/3s, multiply by 3.
What is molecular formula actual number of atoms of each
element in a compound
How to find molecular formula 1) find Mr of empirical
formula<br>2) divide Mr by formula mass of empirical formula<br>3)
multiply answer by empirical formula
reactions for ionic equation acid + metal = salt +
hydrogen<br>acid + carbonate = salt + water + carbon dioxide<br>acid
+ base = salt + water<br>acid + alkali = salt + water
Ionic equation method 1) Separate ions in aqueos ionic
compounds<br>2) Leave solid compounds<br>3) Leave pure metals +
covalent compounds<br>4) Cancel spectator ions<br>5) Balance total
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