Although copper does not usually react with acids, it does...

Although copper does not usually react with acids, it does react with concentrated nitric acid. The reaction is complicated, but one outcome is $$\begin{aligned}\mathrm{Cu}(\mathrm{s})+\mathrm{HNO}_{3}(\mathrm{conc}) \rightarrow \\& \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\mathrm{NO}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\ell)\end{aligned}$$ (a) Name all of the reactants and products. (b) Balance the reaction. (c) Assign oxidation numbers to the atoms. Is this a redox reaction? (d) Pre-1983 pennies were made of pure copper. If such a penny had a mass of $3.10 \mathrm{~g}$, how many moles of Cu are in one penny? How many atoms of copper are in one penny? (e) What mass of $\mathrm{HNO}_{3}$ would be needed to completely react with a pre-1983 penny?

Although copper does not usually react with acids, it does react with concentrated nitric acid. The reaction is complicated, but one outcome is $$\begin{aligned}\mathrm{Cu}(\mathrm{s})+\mathrm{HNO}_{3}(\mathrm{conc}) \rightarrow \\& \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\mathrm{NO}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\ell)\end{aligned}$$
(a) Name all of the reactants and products.
(b) Balance the reaction.
(c) Assign oxidation numbers to the atoms. Is this a redox reaction?
(d) Pre-1983 pennies were made of pure copper. If such a penny had a mass of $3.10 \mathrm{~g}$, how many moles of Cu are in one penny? How many atoms of copper are in one penny?
(e) What mass of $\mathrm{HNO}_{3}$ would be needed to completely react with a pre-1983 penny?

Key Concepts

Stoichiometry and The Mole Concept

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction, using the mole as a counting unit. The mole concept allows chemists to convert between the mass of a substance and the number of particles, typically using Avogadro's number, facilitating precise quantitative calculations in reactions.

Chemical Nomenclature

This concept involves correctly identifying and naming the reactants and products in a chemical reaction. It requires an understanding of chemical formulas and the standard nomenclature rules, which allow one to communicate chemical substances unambiguously.

Balancing Chemical Equations

This is the process of ensuring that the number of atoms for each element is conserved before and after the reaction. It reflects the law of conservation of mass by assigning appropriate stoichiometric coefficients to each reactant and product in the equation.

Oxidation Number Assignment

This involves determining the oxidation state of atoms within chemical species, which helps in tracking how electrons are distributed in a chemical reaction. Assigning oxidation numbers is a critical step in identifying changes in electron density during a reaction.

Redox Reactions

Redox (reduction-oxidation) reactions are chemical processes where electrons are transferred between species. Identifying a redox process involves comparing the oxidation states of elements in the reactants and products to see if any have increased or decreased.

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