.
.
.
(For
experienced chemistry teachers only! Attention! Alkali metals are extremely
corrosive and reactive)
Lithium in a "battery" can
power a digital watch. It can be opened to observe this alkali
metal.
* Observation
left:* The metal can be scratched with a knife.*
2. photo: Water added to the lithium reacts with the metal producing
gas bubbles.
* 3. photo: Lithium
disappears, a clourless solution is left.
* Right photo: The
alkaline solution of this colourless solution is tested in a blister package.
Drops of the solution
are placed into the right and the left blister. Drops of universal indicator
solution (UI)
are added to the
solution in the right blister and to the Blister in the middle.
* Observation:
The indicator changes from orange to violet.
* Explanation:
Lithium reduced water leaving alkaline
solution of lithium hydroxide and hydrogen.
2 Li --ox--> 2 Li+ + 2 e-
|| 2 H2O + 2e- --red--> 2 OH-
+ H2(g)
|| 2 Li(s) + 2 H2O ---> 2 Li+(aq) + 2
OH-(aq) + H2(g)