Transcript Bromate and sulfur dioxide

SO2 gas and BrO3-
Sulfur dioxide gas is
generated by reacting
dilute hydrochloric acid
with solid sodium sulfite.
2HCl(aq) + Na2SO3(s) →
SO2(g) + H2O(l) + 2NaCl(aq)
Is this reaction a redox
reaction? Why/why not?
2HCl(aq) + Na2SO3(s) → SO2(g) + H2O(l) + 2NaCl(aq)
This reaction is not a redox reaction. Sulfur is in the +4
oxidation state in both SO32- and SO2.
This reaction is an acid-base reaction.
The SO2 tube is placed in
a beaker of potassium
bromate solution, which is
colourless.
At this stage no SO2 is
being produced.
As the SO2 begins to
bubble through the
solution, the bromate
solution starts to
change colour.
As SO2 continues to
bubble through, the
colour intensifies to a
deep orange.
SO2 continues to
bubble in, and the
orange colour slowly
fades.
The final solution is
colourless.
Sulfur dioxide is a reducing agent (also known as an
antioxidant in the food and beverage industries). It is
oxidised to SO42-.
Bromine is in the +5 oxidation state in BrO3-.
It is reduced, first to Br2 (which is orange in dilute
solution),
which is further reduced to colourless Br-.
BrO3
-
Br2
Br-
SO2(g) + 2H2O(l) → SO42-(aq) + 4H+(aq) + 2e2BrO3-(aq) + 12H+(aq) + 10e- → Br2(aq) + 6H2O
5SO2 + 4H2O + 2BrO3- → 5SO42- + 8H+ + Br2
SO2(g) + 2H2O(l) → SO42-(aq) + 4H+(aq) + 2eBr2(aq) + 2e- → 2BrBr2 + SO2 + 2H2O → 2Br- + SO42- + 4H+
Potassium bromate and potassium iodate are important
oxidising agents because they are available in very pure
form.
In most reactions involving bromate or iodate it is
necessary to add acid.
2BrO3-(aq) + 12H+(aq) + 10e- → Br2(aq) + 6H2O