Write balanced chemical equations for the following reactions: (a) zinc metal heated in a stream of oxygen gas (b) zinc carbonate heated until loss of mass stops (c) zinc carbonate added to a solution of acetic acid, \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) (d) zinc added to a solution of hydrobromic acid

Zinc, a transition metal with the symbol Zn, is a versatile element that engages in various chemical reactions. One such reaction is when zinc metal is heated in the presence of oxygen gas, which results in the formation of zinc oxide (\text{ZnO}). The chemical equation for this process is balanced to show that two moles of zinc react with one mole of oxygen gas to produce two moles of zinc oxide, represented as 2 Zn + O\(_2\) -> 2 ZnO. Another common zinc reaction is with an acid, such as hydrobromic acid, where zinc displaces hydrogen, forming zinc bromide (\text{ZnBr}\(_2\)) and hydrogen gas. The balancing of this equation, Zn + 2 HBr -> ZnBr\(_2\) + H\(_2\), ensures the conservation of mass and atoms according to the law of conservation of matter. These examples illustrate the reactivity of zinc and its ability to form compounds through different types of chemical reactions.

Decomposition reactions involve the breakdown of a compound into two or more simpler substances. When zinc carbonate (\text{ZnCO}\(_3\)) is heated until mass loss stops, it undergoes a decomposition reaction to form zinc oxide (ZnO) and carbon dioxide (CO\(_2\)). The reaction is represented by ZnCO\(_3\) -> ZnO + CO\(_2\). Decomposition reactions are often endothermic, requiring energy input, usually in the form of heat, to proceed. The balanced equation demonstrates that one mole of zinc carbonate decomposes to yield one mole of zinc oxide and one mole of carbon dioxide, showcasing the stoichiometry of the reaction without the need for further balancing.

Acid-base reactions are characterized by the exchange of a proton (\text{H}+) between an acid and a base. In the given exercise, zinc carbonate (\text{ZnCO}\(_3\)) reacts with acetic acid (\text{CH}\(_3\)CO\(_2\)H) to form zinc acetate (\text{Zn(CH}\(_3\)CO\(_2\))\(_2\)), carbon dioxide (CO\(_2\)), and water (H\(_2\)O). The key to balancing this type of reaction is recognizing that acetic acid donates a proton to the zinc carbonate, which acts as a base. To balance the equation, it is essential to ensure the number of acetic acid molecules equals the number of acetate ions in the zinc acetate produced. The resulting balanced equation is ZnCO\(_3\) + 2 CH\(_3\)CO\(_2\)H -> Zn(CH\(_3\)CO\(_2\))\(_2\) + CO\(_2\) + H\(_2\)O, obeying the law of conservation of mass.

Stoichiometry is the study of the quantitative aspects of chemical reactions, involving the calculation of reactants and products in a chemical equation. It is founded on the conservation of mass and the concept of the mole. For instance, balancing the reaction between zinc and hydrobromic acid to form zinc bromide and hydrogen gas requires stoichiometric calculations. The balanced chemical equation, Zn + 2 HBr -> ZnBr\(_2\) + H\(_2\), informs us that one mole of zinc reacts with two moles of hydrobromic acid to produce one mole of zinc bromide and one mole of hydrogen gas. This quantitative relationship is crucial for predicting product formation and reactant consumption in any chemical reaction. When students grasp the fundamentals of stoichiometry, they gain the ability to methodically balance equations and predict the outcomes of chemical processes.