Steve Marsden’s

One of the more spectacular and interesting of the reactions you saw was what happens to alkali metals in water. Alkali metals like lithium, sodium, etc., are all placed above hydrogen in the activity series and thus are able to displace hydrogen from acids and even water.

The hydrogen displacement from water occurs as if water were H+OH- (it is not, of course, since water is a molecular compound). So the general molecular form for the reaction of water with alkali metals would be:

2 M + 2 H2O ® H2 + 2 MOH

The presence of OH- ions accounts for the fact that bromthymol blue shows the final mixture to be basic.

So what do the reactions of Li and Na with water look like?