Chlorine gas was first prepared in 1774 by C. W. Scheele by oxidizing sodium chloride with manganese(IV) oxide. The reaction is \(\begin{aligned} \mathrm{NaCl}(a q)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{MnO}_{2}(s) \longrightarrow & \mathrm{MnCl}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{Cl}_{2}(g) \end{aligned}\) Balance this equation.

A chemical reaction is a process where reactants are transformed into new substances, known as products. During this transformation, chemical bonds are broken and new bonds are formed. The chlorine gas preparation you've encountered in your exercise is a classic example of a chemical reaction, where chlorine gas is produced through the interaction of sodium chloride, sulfuric acid, and manganese(IV) oxide.

To understand a chemical reaction, it's crucial to look at the substances involved before and after the reaction. For our exercise, the reactants are NaCl (aqueous), H2SO4 (aqueous), and MnO2 (solid), while the products are MnCl2 (aqueous), H2O (liquid), and Cl2 (gas). The balancing of this equation requires careful accounting of each atom type on both sides of the equation to ensure they are equal, reflecting the conservation of matter.

Stoichiometry is the quantitative relationship between the amounts of reactants and products in a chemical reaction. It's based on the principle that matter cannot be created or destroyed in chemical reactions (the law of conservation of mass). When resolving stoichiometric problems, such as balancing the provided chemical equation, one must ensure that the number of atoms for each element involved in the reaction is the same on both sides of the equation.

In our exercise, stoichiometry was used to determine the correct coefficients for reactants and products. This ensures that the amounts of sodium, chlorine, hydrogen, manganese, and oxygen atoms are conserved from reactants to products. The balancing steps you went through systematically adjusted coefficients to achieve this conservation. The step-by-step process exemplifies stoichiometrical calculations that are essential in predicting yields of reactions and understanding the proportions of substances required.

Oxidation-reduction (redox) reactions are a subset of chemical reactions involving the transfer of electrons between two species. Oxidation is the loss of electrons, while reduction is the gain of electrons. These reactions play a significant role in chemistry, including biological processes, energy storage, and corrosion.

In the context of our exercise, the preparation of chlorine gas can be viewed as a redox reaction. Manganese(IV) oxide (MnO2) acts as an oxidizing agent and loses electrons (is reduced) while sodium chloride (NaCl) is the source of chlorine which is oxidized to form chlorine gas (Cl2). The successful balancing of the equation reflects the nuances of redox balancing, where attention must be paid to both mass and charge conservation. Balancing redox reactions involves additional steps compared to other reactions because both the number of atoms and the charges must balance, which adds another layer of complexity to the stoichiometric calculations.