what acidsenvolved?

Question

what acids involved hydrogen when acted upon by metals?

and why?

Answer 1

you need to have an active metal (that is one that has a lower potential than H+, so that H2 can be made, see http://en.wikipedia.org/wiki/Table_of_standard_electrode_potentials, every metal with a "-" will react with an acid to produce hydrogen). Metals with a positive standard electrode potential (with a "+" in the table) will not react with acids to produce hydrogen, instead, they will react with oxidizing acids to produce reduced acid anhydrides (like SO2 from H2SO4 and NO2 or NO from HNO3). Some metals (like aluminum) will passivate in oxidizing acids (form Al2O3) and react like noble metals (evolving SO2 and nitrogen oxides)

Answer 2

The H+ ion can be reduced by reactive metals to hydrogen gas. Acids produce H+ ions when they dissolve in water.