3.1.2 Amount of substance Flashcards
The mole
The amount of substance in grams that has the same amount
of particles as there are atoms in 12g of carbon-12
Relative Atomic Mass (Ar)
The average mass of an atom compared to 1/12 the mass of
an atom of carbon-12
Relative Molecular Mass (Mr)
The average mass of a molecule compared to 1/12 the mass
of an atom of carbon-12
Relative Formula Mass (RFM)
The average mass of an ionic compound compared to 1/12
the mass of an atom of carbon-12
Avogadro’s Constant
The number of particles in one mole
Avogadro’s Number
6.022 * 10^23
Molar Equations: M, Mr, n
Mass = moles * Mr Mr = mass/moles (n) Moles = Mass/Mr
Molar Equations: n, c, v
Moles = concentration * volume Concentration = moles/volume Volume = moles/concentration
Converting Volumes
Volumes must be converted to dm^3
cm^3 to dm^3
(cm^3/1000)
dm^3 to cm^3
(dm^3 * 1000)
Molar Equations: number of particles, n, avogadro’s number
Number of Particles = moles * l (l is avogadro’s number)
Moles = Number of particles/l
l= Number of particles/moles
Empirical Formula
The simplest whole number ratio of atoms of each element in
a compound
How to work out Emp. Formula
-Find n of elements by dividing mass by Mr
-Divide each mole value by the smallest one to determine the
ratio
-Determine the whole number ratio of each element
Water of Crystallisation
- Find mass of water by subtracting anhydrous from hydrated
- Find moles of anhydrous substance (use mass/Mr)
- Find moles of water (use Mass/Mr)
- Determine the ratio
