# Fundamental Ideas 2

Relative Atomic Mass definition
The average mass of an atom compared with the mass of an atom of Carbon-12.
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Relative Molecular Mass definition
The sum of the relative atomic masses of the atoms making up a molecule.
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Relative Formula Mass definition
The sum of the relative atomic masses of the atoms making up a compound containing ions.
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Mole definition
1 mole is the amount of a substance which is made up of the same number of particles as there are carbon atoms in 12g of carbon-12.
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6.02 x 10^23, this is the number of carbon atoms in 12g of carbon-12.
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How to find the number of moles in a substance
Number of moles = mass (g) / mass of 1 mole (molecular mass)
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Empirical formula definition
The simplest whole number ratio of atoms in a substance.
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Percentage composition definition
The percentage of a substance made up by one element.
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How to find percentage composition
Mass of element you want / molecular mass of whole molecule * 100
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How to calculate percentage yield
Actual yield / theoretical yield * 100
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3 reasons theoretical yield not obtained
Reaction could be reversible, some product may be lost, some of the reactants might react differently to expected.
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## Other cards in this set

### Card 2

#### Front

Relative Molecular Mass definition

#### Back

The sum of the relative atomic masses of the atoms making up a molecule.

### Card 3

#### Front

Relative Formula Mass definition

Mole definition