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Slide 1

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Chemistry Calculations
t io n , R e la t i v e
le Sc Titra
GCS Formula Mass,
E e n t a g e Y i e l d e .c.
t.…read more

Slide 2

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Mass And Isotopes
Mass number = total number of protons + neutrons
in an atom.
Atomic number = number of protons in a atom
Isotopes contain the same number of protons and
electrons as the atom, but different numbers of
Relative atomic mass = mass number
Relative formula mass = all mass numbers added
together in formula
Relative formula mass = one mole of that substance…read more

Slide 3

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Percentage Composition
This is used to work out how much of an element
there is in each compound to do this we:
1.Work out the relative formula mass.
2.Divide the relative atomic mass by the relative
formula mass.
3.To make this a percentage multiply by 100
4.If there are more than one of the atoms in the
compound multiply answer by the number of atoms…read more

Slide 4

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An Example Of Percentage Composition
What is the percentage mass of Mg in Magnesium
Relative atomic mass of Mg = 24
Relative atomic mass of MgO = 24+16=40
(24/40) x 100 = 60%
So Mg makes up 60% of the compound.…read more

Slide 5

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Conservation Of Mass
Though out a reaction to overall mass does not
lessen or increase, as a reaction does not introduce
new atoms.
This means you can work out the other masses if one
is know.
However reversible reactions may not go to
completion, some products may be lost or reactants
may react in an unexpected way.…read more

Slide 6

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Atom Economy
The atom economy is the percentage of useful
products in a compound, this is worked out like a
If a product has a high atom economy it is good for a
sustainable development.
We can work this out by:
The mass of desired products/Mass of reactants x 100 = Atom Economy…read more

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