Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Redox reactions
Oxidation States

1
...

E
...


2
...
g
...

E
...


3
...

E
...
Na = +1, Cl = -1
...
g
...

E
...
SO3 = -2

Sometimes the oxidation number for an element may be
different in different compounds
...


In H2SO4;
« O = -2
...
H2 = +1 x 2 = +2
« H2 + O4 = -8 + +2 = -6
« For the oxidation state of H2SO4 to be 0 overall, S
must be +6
...
O3 = -2 x 3 = -6
« Na = +1
« Na + O3 = -6 + +1 = -5
« For the oxidation state of NaSO3 to be 0 overall, S
must be +5
...
The change in oxidation state of an

atom shows if it has been oxidized or reduced during a
reaction
...

Reduction; "a decrease in oxidation number" or gaining
electrons and becoming more negative
...
Once
bonded in the compound NaCl, it's oxidation
number is +1
...

∙ The Cl starts with an oxidation number of 0 (It is
also in its elemental form and is not an ion)
...
It has
decreased in oxidation number and so has been
reduced
...

Similarly, the substance that caused the reduction of Cl
Is the Na, and therefore the N
...
is the reducing agent
...

The element which has been oxidized is simultaneously
the reducing agent
...
These
reactions where oxidation and reduction occur are called
Redox reactions
...
What is the oxidation state of sulphur (S) in the
following compounds and ions?
a) H2S
b) SO2
c) SO3
d) H2SO4
e) SO3 2f) SO4 2-

2
...

a) H2 + Cl 2 ----> 2HCl
b) Mg + 2HCl ----> MgCl2 + H2

(Scroll down for answers)

Answers
1
...

a) H has been oxidized, Cl has been reduced
b) Mg has been oxidized, H has been reduced, Cl
remains the same



---