Would CaO + H20 -- Ca(OH)2 be a displacement reaction? if not what would it be and why?

Question

Would CaO + H20 --> Ca(OH)2 be a displacement reaction? if not what would it be and why?

anonymous · Answer

It's an acid-base reaction.  CaO, like most of the metal oxides from the left side of the Periodic Table, is a basic oxide.  So it reacts with water as any base would, generating OH-.  You start with a solid (CaO) and add water, and you end up with Ca+2 and lots of OH- in solution -- a very alkaline solution.

You may wonder where the proton transfer, if any, happens, and it happens when the CaO dissolves, as it does, bit by bit, as the reaction proceeds.  This releases the Ca+2 and O-2 ions.  The latter is a powerful base, and immediately rips an H+ off the nearest water:
$${\rm O}_{2}^{2-}(aq) + {\rm H}_2{\rm O}(l) \rightarrow 2 {\rm OH}^-(aq)$$
In this reaction the H2O is acting as the Bronsted-Lowry acid.

jfraser · Answer

you could also get away with calling this a synthesis reaction, since you start with more than one reactant and finish with only 1 product

anonymous · Answer

Oops, the first reaction in my reaction should be $${\rm O}^{2-}(aq)$$.

anonymous · Answer

"Reactant," that is.

anonymous · Answer

Displacement reactions normally concern that a higher substance in the reactivity series will displace the one which is lower