How to obtain the result of a chemical reaction given two components?

Solution 1:

Yes, Google.

If somebody's put the result of the reaction on the net, google will know about it. Doing the reactions of any two elements accurately and definitively would basically require somebody to program a universe simulator, wheras we already have a perfectly good universe to test things out manually, right here.

edit: CW so people can downvote me, this answer really isn't deserving of a bounty, on the offchance to OP doesn't return in time.

Solution 2:

Would this Chemical Equations Calculator do? If not, there is a lot of hits returned for the search "chemical reaction calculator online".

Solution 3:

Computational Chemistry -- that is, simulating the chemical reactions rather than simply having a database of reactants -- is well known as one of the classic supercomputer CPU sinks. Wikipedia has an introduction, and Google will give the expected large number of links.