Topic 2 - Foundations in chemistry
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Definition of Relative Atomic Mass (Ar)
Weighted mean mass of an atom relative to 1/12th the mass of an atom of carbon 12
Definition of Relative Formula Mass (Mr)
The term used when working out the calculation for compounds with giant structures
Name 3 types of giant structures
Giant Ionic Giant Covalent Giant Metallic
Definition of Relative Molecular Mass
The term used when working out the calculation for compounds that are simple molecules
Name a type of simple molecular structure
Covalent Compounds
What is the formula for finding out how much of a compound is made up of a particular element?
% of element = ((number of atoms of element x relative atomic mass of the element) / relative formula mass of compound) x 100
What is the molar mass?
.The mass per mol of a substance in g mol^-1 .Same number as Mr
What is the amount of substance + unit?
.A means of counting the number of particles in a substance .Unit is the mol
What is Avogadro’s Constant?
(NA) 6.02x10^23 mol-1
What is everything measured relative to?
Carbon-12
Define the mole
The amount of any substance containing as many elementary particles as there are carbon atoms in 12 grams of carbon-12 (6.02x10^23) particles
number of mols (mol) =
mass (g) / molar mass (g mol-1)
Smallest mass of an atom
1.67x10^-27
The largest mass of an atom
4.52x10^-25
What do we use the smallest mass of an atom to do?
Produce a relative scale called the unified atomic mass unit ‘u’ = 1.67x10^-27
If hydrogen-1 = 1u, what does carbon-12 =?
12u
Define relative isotopic mass
The mass of an atom of an isotope relative to 1/12th the mass of a carbon 12 atom
What is 1/12th the mass of a carbon-12 atom?
1u
Define relative atomic mass
The relative atomic mass is the ‘weighted mean’ mass of an atom relative to 1/12th the mass of a carbon-12 atom
formula to find out relative atomic mass/weighted mean?
((mass x abundance) + (mass x abundance)) / 100
Define molecular formula
The number and type of atoms of each element in a molecule
Define empirical formula
Shows the simplest whole number ration of atoms of each element in a compound
State the steps for finding the empirical formula
• find the mass • calculate the moles • divide all the results by the smallest value to get the ration • adjust the ratio to get whole numbers • workout the empirical formula
What is water of crystallisation?
Water molecules that are bonded into a crystalline structure of a compound