Does adding chromium and sulfuric acid together make a reaction? What about aluminum bromide and magnesium?

Answer 1

Cr is high enough in the activity series that it will displace hydrogen ion from the acid. Mg metal is above Al in the activity series; therefore, Mg metal will displace aluminum ion from AlBr3.

Answer 2

Here is a site that gives the activity series.

http://en.wikipedia.org/wiki/Reactivity_series