Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
-----------------
sulphuric acid : H2SO4
sodium bromide : NaBr
sodium chloride : NaCl
Class:
------
elem=Cl,Br
redox
Summary:
--------
Sodium chloride reacts with sulfuric acid to give hydrogen chloride gas.
Sodium bromide shows a similar reaction, producing hydrogen bromide, but
in a side reaction some bromine is formed.
Description:
------------
Sequence 1:
-----------
Add some concentrated sulfuric acid (appr. 98%) to some solid NaCl: A
vigorous reaction occurs, a lot of gas is produced, the liquid starts
foaming. A noticeable amount of heat is produced as well.
The gas, which is produced, is colorless. On contact with air it produces
thick white fumes with a choking odour (not like chlorine, just stinging).
This gas is HCl (hydrogen chloride).
When the test tube is put under water, bottom up, then appr. three quarters
of the volume of the gas mixture in the tube are replaced by water. The HCl
gas dissolves in the water.
Sequence 2:
-----------
Add some concentrated sulfuric acid (appr. 98 %) to some solid NaBr: A
vigorous reaction occurs, a lot of gas is produced, the liquid starts
foaming. A noticeable amount of heat is produced as well.
Here, however, the gas is not colorless, but it has a brownish orange color.
Some Br2 is formed, although not very much. On contact with air, the gas
mixture produces a thick white fume with an extremely strong choking odour
(even more choking than HCl).
When the test tube is put under water, bottom up, then again a large part of
the gas mixture in the test tube is replaced by water. Now the orange color
of the free bromine immediately disappears again. Probably the bromine was
formed with the other product being SO2. In contact with water these react
again, forming bromide and sulfuric acid.