Zusammenfassung der Ressource
Unit 3: Quantitative Chemistry
- Relative Formula Mass
- The relative mass is just the relative atomic
masses of all of the elements in the molecular
formula added together.
- Percentage of mass
of an element in a
compound =
- Ar x number of atoms of that element
____________________________________________________ x 100
Mr of the compound
- The Mole and Mass
- One mole of any substance is just
the amount of the substance that
contains an Avogadro number of
particles.
- This means that there are the
same number and same type of
atoms on each side of the
reaction equation.
- Because of this, no mass is lost or gained,
we say the mass is conserved during a
reaction.
- E,g. 2LI + F2 = 2LiF
- Avogadro Constant = 6.02 x 10↑23
- E,g. Carbon has an A of 12g. So one
mole of carbon weighs exactly 12g.
- Number of Moles =
- mass in g (of an element or compound
----------------------------------------------------------------------------
Mr (of the element or compound
- In a chemical reaction,
mass is always conserved.
- During a chemical reaction, no atoms
are destroyed and no atoms are
created.
- if a mass seems to change, there's
normally a gas involved..
- The Mole and Equations
- The numbers in chemical
equations mean different
things.
- You can balance equations using reacting masses.
- Reactions stop when one reactant is used up.
- Volume of gas =
- Mass of gas
------------------
Mr of gas