What must be done to the following half-reactions before they can be added together? mn (s) → mn 2+ (aq) + 2e − fe 3+ (aq) + 3e − → fe (s)double the mn half-reaction and triple the fe half-reaction. add h+ ions to the left-side of the mn reaction. triple the mn half-reaction and double the fe half-reaction. double the mn half-reaction. none of the above

The gas would begin to expand, and eventually the can would burst or explode.

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na