Download I.E.S. Gabriela Mistral Leyre González López Oxyacids These are

I.E.S. Gabriela Mistral
Leyre González López
Oxyacids
These are compounds with the following general formula:
HaXbOc
where

X is a non metal with a positive oxidation number. X can also be a transition metal with a
high oxidation number, such as Cr(+6), Mn(+6) or Mn(+7).

H has an oxidation number of +1.

O has an oxidation number of -2.
How do we know the oxidation number of X?
To know the oxidation number of X, remember that the addition of all the oxidation numbers must
be 0. For example:
H2SO4: (+1)∙2 + x + (-2)∙4=0 → x=+6 → S has an oxidation number of +6
How are they formed?
They are obtained by adding one molecule of water to an oxide. For example, if we want to form
the oxyacid of S in which it has an oxidation number of +6 we do the following steps:

We form the oxide.
S2O6 → SO3

We add a molecule of water (the molecule we obtain is simplified if necessary).
SO3 + H2O → H2SO4
Let´s see another example. Let´s form the oxyacid of Cl in which this element has an oxidation
number of +3:

We form the oxide: Cl2O3

We add one molecule of water and in this case we will need to simplify:
Cl2O3 + H2O → H2Cl2O4 → HClO2
How are they named?
Root of X with suffixes and prefixes which indicate its oxidation number + “acid”
The suffixes and prefixes used are:
1. If X has 1 oxidation number:
-ic
2. If X has 2 oxidation numbers:
-ous for the smallest
-ic for the biggest
3. If X has 3 oxidation numbers:
hypo- -ous for the smallest
-ous for the middle one
4. If X has 4 oxidation numbers:
hypo- -ous for the smallest
-ous for the middle smallest one
-ic for the middle biggest one
per- -ic for the biggest
-ic for the biggest
En español:
“ácido” + raíz de X con prefijos y sufijos que indican su estado de oxidación
Los prefijos y sufijos a usar son:

Si X tiene 1 estado de oxidación:
-ico

Si X tiene 2 estados de oxidación:
-oso para el menor

Si X tiene 3 estados de oxidación:
hipo- -oso para el menor

-ico para el mayor
-oso para el mediano
-ico para el mayor
Si X tiene 4 estados de oxidación:
hipo- -oso para el menor
-oso para el mediano menor
-ico para el mediano mayor
per- -ico para el mayor
Let´s see some examples:

S has +2, +4 and +6 as oxidation numbers.
In H2SO4, S has an oxidation number of +6 (the biggest), so H2SO4 is sulphuric acid (ácido
sulfúrico).

Cl has +1, +3, +5 and +7 as oxidation numbers.
In HClO2, Cl has an oxidation number of +3 (the middle smallest one), so HClO2 is chlorous acid
(ácido cloroso).

In HBrO4, Br has an oxidation number of +7 (Br has 4 oxidation numbers and +7 is the
biggest one), so HBrO4 is perbromic acid (ácido perbrómico).

In HIO, I has an oxidation number of +1 (I has 4 oxidation numbers and +1 is the smallest
one), so HIO is hypoiodous acid (ácido hipoyodoso).
Exercises
1. Write the formula of the following oxyacids:
a) perchloric acid
b) sulphurous acid
c) nitric acid
d) nitrous acid
e) carbonic acid
f) chloric acid
2. Write the name of the following oxyacids:
a) HBrO
b) H2SeO3
c) HClO4
d) H2SO2
e) H2TeO4
f) HBrO3