2. Amount Of Substance
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Why are all mass relative to carbon-12?
1/12 of its relative atomic mass is 1
How can relative atomic mass (Ar) be defined?
The weighted average mass of an atom of an element, taking into account its isotopes, relative to 1/12 of the relative atomic mass of an atom of carbon-12
How can relative atomic mass be calculated?
average mass of one atom of an element / 1/12 mass of one atom of carbon-12
How can relative molecular mass (Mr) be defined?
The mass of that molecule compared to 1/12 of the relative atomic mass of an atom of carbon-12
How can relative molecular mass be calculated?
average mass of one molecule / 1/12 mass of one atom of carbon-12
What do ionic compounds exist as instead of molecules?
Ionic lattices
What is used for ionic compounds instead of relative molecular mass?
Relative formula mass
Why is relative formula mass used for ionic compounds?
They form ionic lattices instead of molecules
What does the formula of an ionic compound show?
The simplest ratio of ions in the compound instead of the total number of atoms in the compound
What is the mole defined as?
The amount of substance that contains 6.022e23 particles
How many particles are in one mole of a subtance?
6.022e23 (electrons, atoms, molecules, ions or compounds)
What equation is used to work out number of moles (using mass and mr)?
n = mass / mr
What is the final answer usually given to?
3 significant figures
How many decimal places should Mr be calculated to?
1
What is the concentration of a solution?
The amount of solute present in a fixed quantity of solvent
What is concentration measured in?
g/dm³ or mol/dm³
What is the molarity?
The concentration (in mol/dm³)
How can number of moles be calculated (when given conc. and volume)?
n=cv
g/dm³ to mol/dm³?
÷ Mr
mol/dm³ to g/dm³?
x Mr
What is a titration?
The procedure of reacting volumes
During a titration, what is placed in the burette?
The solution of known concentration
During a titration, what is placed in the conical flask?
The solution of unknown concentration
What is the law of conservation of mass?
Mass of reactants = Mass of products