Chromium metal is added to a solution of nickel(ii) sulfate. what is the balanced chemical reaction? hints

(a)Nickel metal is added to a solution of copper (II) nitrate We have elemental Ni and Cu2+(aq); on the activity series, Ni is above Cu. Therefore, Ni will be oxidized to the +2 ion (look on the activity series) by Cu2+(aq), and the Cu2+ will be reduced to elemental Cu: Ni(s) + Cu2+(aq) --> Ni2+(aq) + Cu(s) This is a prime example of a single displacement reaction! (b) A solution of zinc nitrate is added to a solution of magnesium sulfate Here, we have aq solutions of Zn2+ and Mg2+. This is not a sinlge displacement reaction - neither of the reactant metals are in elemental form. This is a NR case - it is a double displacement reaction in which neither of the prodcuts are insoluble (why?) (c) Hydrochloric acid is added to gold metal Lok at the activity series: Au is at the very bottom. Au is below hydrogen and so will not react with hydrogen ions (H+). So this is an NR. (d) Hydrogen gas is bubbled through a solution of silver nitrate Here, we have elemental hydrogen and a solution of Ag+. Silver is below hydrogen on the activity series, so silver (I) ions will oxidize hydrogen gas. In net ionic form (be sure to work this one out!!!) 2Ag+(aq) + H2(g) --> 2Ag(s) + 2H+(aq)