A copper penny can be dissolved in nitric acid but not in hydrochloric acid. Using reduction potentials from the book, show why this is so. What are the products of the reaction? Newer pennies contain a mixture of zinc and copper. What happens to the zinc in the penny when the coin is placed in nitric acid? Hydrochloric acid? Support your explanations with data from the book, and include balanced equations for all reactions.

We will use the half-reaction potentials for Cu, Zn, HNO3, and HCl. We can find these values from the book or other reference materials. Copper: \(Cu^{2+}(aq) + 2e^- \rightarrow Cu(s)\), \(E^0 = +0.34 V\) Zinc: \(Zn^{2+}(aq) + 2e^- \rightarrow Zn(s)\), \(E^0 = -0.76 V\) Nitric Acid: \(NO_3^-(aq) + 4H^+(aq) + 3e^- \rightarrow NO(g) + 2H_2O(l)\), \(E^0 = +0.96 V\) Hydrochloric Acid: \(2H^+(aq) + 2e^- \rightarrow H_2(g)\), \(E^0 = 0 V\)

Calculate the overall cell potential for both the Cu and Zn reactions with HNO3 and HCl. Cell potential (E cell): For a redox reaction, the overall cell potential can be calculated as \(E_{cell} = E_{reduction} - E_{oxidation}\). Copper and Nitric Acid: \(E_{cell} = (+0.96 V) - (+0.34 V) = +0.62 V\) Copper and Hydrochloric Acid: \(E_{cell} = (0 V) - (+0.34 V) = -0.34 V\) Zinc and Nitric Acid: \(E_{cell} = (+0.96 V) - (-0.76 V) = +1.72 V\) Zinc and Hydrochloric Acid: \(E_{cell} = (0 V) - (-0.76 V) = +0.76 V\)

As observed in Step 2, the copper and nitric acid reaction has a positive cell potential (+0.62 V), indicating that the reaction is spontaneous and favors the formation of products. The copper and hydrochloric acid reaction has a negative cell potential (-0.34 V), which means the reaction is non-spontaneous and doesn't proceed in the forward direction. Thus, copper can dissolve in nitric acid but not in hydrochloric acid.

The products of the copper and nitric acid reaction are aqueous copper(II) ions, gaseous nitrogen monoxide, and water. The balanced equation for this reaction is: \(3Cu(s) + 8HNO_3(aq) \rightarrow 3Cu^{2+}(aq) + 2NO(g) + 4H_2O(l) + 6NO_3^-(aq)\)

As calculated in Step 2, both the zinc and nitric acid, and zinc and hydrochloric acid reactions have positive cell potentials (+1.72 V and +0.76 V, respectively), which indicates that both reactions are spontaneous and will proceed in the forward direction. The balanced equation for the zinc and nitric acid reaction is: \(Zn(s) + 2HNO_3(aq) \rightarrow Zn^{2+}(aq) + 2NO_3^-(aq) + NO(g) + H_2O(l)\) The balanced equation for the zinc and hydrochloric acid reaction is: \(Zn(s) + 2HCl(aq) \rightarrow Zn^{2+}(aq) + 2Cl^-(aq) + H_2(g)\) Therefore, both zinc and copper will dissolve in nitric acid, with the products being the corresponding metal ions, gaseous nitrogen monoxide, water, and nitrate ions. In hydrochloric acid, only zinc will dissolve, producing zinc ions, chloride ions, and hydrogen gas.