Utilizing the activity series, state balanced chemical equations for the following reactions. If not reaction takes place, just write NR.
(a) Nickel metal is added to a solution of copper(II) nitrate
(b) A solution of zinc nitrate is added to a solution of magnesium sulfate.
(c) Hydrochloric acid is added to gold metal
(d) Chromium metal is immersed in an aqueous solution of cobalt(II) chloride
(e) Hydrogen gas is bubbled through a solution of silver nitrate