Formulae and reacting quantities Flashcards
Elements in compounds ending in -ide
contain the two elements indicated by the name
Talk about compounds ending in -ate or -ite
contain the elements indicated by the name and oxygen
What are the prefixes in chemical formulae?
mono 1
di 2
tri 3
tetra 4
penta 5
hexa 6
How to write a basic chemical formula
write down the symbols of both the elements involved
beneath each symbol write the valency
swap the valencies over
if the valencies can be simplified divide them both by the smaller of the two numbers
What are group ions?
Group ions contain two or more atoms, and most of them have a negative charge
Roman numerals 1-6
I
II
III
IV
V
VI
when should brackets be used in a chemical formula
When a formula contains more than one group ion, the group ion must be written in brackets
When using Roman numerals to write the chemical formula what must we still do?
cross over the valencies
What is the state symbol for a solid?
(s)
What is the state symbol for a liquid?
(l)
What is the state symbol for a gas?
(g)
What is the state symbol for an aqueous solution?
(aq)
For most elements, 1 mole is what?
relative atomic mass in grams
For the diatomic elements 1 mole is what?
twice the relative atomic mass in grams
Formula triangle for solids, liquids and gases…
number of moles = mass in grams/ mass of one mole
n=m/GFM
Formula triangle for solutions…
concentration of solution in mol l-1 = number of moles of solute / volume of solution in litres
(c=n/v)
What does a chemical formula tell us?
the number of atoms in a molecule of a covalent compound or the ratio of ions in an ionic compound
What is percentage composition?
the percentage mass of each element present
What formula can be used to calculate percentage by mass
% by mass = m/GFM x 100
m represents the mass of the element that is present in the compound in grams
Give an example of a percentage composition question…
Calculate the percentage by mass of oxygen in 1 mole of water (H2O).
GFM of H2O = 18
% by mass of O in H2O= 16/18 x100
Two elements which do not contain oxygen will always end in what?
-ide
What is the valency of zinc always
2
If dealing with prefixes in chemical formulae what must one remember?
do not simplify the valencies
the prefix applies the valency of the element to which it was attached (do not cross the valencies)
What is an aqueous solution
compound dissolved in water
When balancing chemical equations how do we know if we have a group ion?
The elements will be together (not split up) on either side of the equation
