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
Molecular Formula
-Determine the number of empirical formula units that can fit
into the Mr (Mr Molecular formula / Mr Empirical Formula)
-Multiply the empirical formula by the units
Percentage Yield
Actual Yield/Theoretic Yield * 100
Percentage Atom Economy
Mass of useful products / mass of all reactants * 100
Ideal Gas Equation: What is it?
PV=nRT
Ideal Gas Equation: Conversion of Pressure (kPa - Pa)
100kPa = 100,000 Pa
Ideal Gas Equation: Conversion of Volume (dm^3/cm^3 to
m^3)
cm^3 to m^3 = x/1000000
dm^3 to m^3 = x/1000
Ideal Gas Equation: Conversion of Temperature (degrees
Celsius to Kelvin & Kelvin to degrees Celsius)
x (degrees Celsius) + 273 = K
x (K) - 273 = degrees Celsius
Cations
Ions with a positive charge
Anions
Ions with a negative charge
State Symbols: (s)
Solid
State Symbols: (l)
Liquid
State Symbols: (g)
Gaseous
State Symbols: (aq)
Aqueous/dissolved in water
State Symbols
Must be included in every chemical equation
Spectator Ions
Ions that stay in the same state throughout the equation. You
can cancel these out if they come up.
