C3 Stoichometry Flashcards
(26 cards)
Ar
Relative atomic mass - average mass of isotopes compared to 1/12 of 12C
- for elements
Mr
Relative molecular/formula mass - sum of relative atomic masses (g/mol)
- for compounds
- of covalent molecules= relative molecular mass
- of ionic compounds = relative formula mass
Number of particles/atoms/molecules present
= moles x Avogadro constant (n x NA)
Calculating Ar
Ar = ((%1 x mass1) + (%2 x mass2)) / 100
Isotope
atoms of same element with same protons/electrons, different neutrons
- answer has to be between the 2 mass’s Mr of Ar of isotopes
Law of Conservation
Mass is neither created nor destroyed
e.g. 2Cu + O2 → 2CuO | 64g + 16g → 80g |128g + 32g → 169g
% Purity
(Mass of pure substance in it/ total mass) x 100
- answer can’t be over 100%
% Yield (the amount of product obtained in a chemical reaction)
(Actual mass of product / Theoretical mass) x 100
Mole
Unit of amount of substance in compound (mol)
Avogadro Constant (Na)
6.02 x 10^23 particles
Mole Formula
n = m / Mr
mol = g/mol
m = n x mr
mr = m/n
Concentration
Amount of substance per volume (g/cm3)
OR
c = n / v | mol/dm3
Solution
Solute dissolved in solvent (homogeneous mixture)
Valency
Number of electrons gained/lost/shared to form compound
Ion
Charged particle (cation or anion) - exist only in aqueous solutions
Oxidation State
Must add to 0 in compounds; 0 in elements
Spectator Ions
Do not get involved in the reaction
Empirical Formula
Simplest whole-number ratio of elements present in that compound
- Calculate the number of moles
- Compare as a ratio of moles
- Reduce to the simplest whole number (integer) ratio
Molecular Formula
number and type of atoms in one molecule
Limiting Reagent
fully consumed and determines the yield
Excess Reagent
Not totally used up, in excess - has more than is needed to react
Addition
One product formed
Decomposition
One reactant breaks down
Combustion
Reaction with oxygen (fuel)
