What is wrong or ambiguous with each of the statements here? (a) \(\mathrm{NH}_{4} \mathrm{NO}_{2}\) is the limiting reactant in the reaction$$\mathrm{NH}_{4} \mathrm{NO}_{2}(s) \longrightarrow \mathrm{N}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l)$$ (b) The limiting reactants for the reaction shown here are \(\mathrm{NH}_{3}\) and \(\mathrm{NaCl}\). $$\begin{aligned}\mathrm{NH}_{3}(a q)+\mathrm{NaCl}(a q) &+\mathrm{H}_{2} \mathrm{CO}_{3}(a q) & \longrightarrow \\ & \mathrm{NaHCO}_{3}(a q)+\mathrm{NH}_{4} \mathrm{Cl}(a q) \end{aligned}$$

A chemical reaction is a process where substances (reactants) are transformed into new substances (products). Understanding the nature of chemical reactions is vital for mastering chemistry. Reactants interact through chemical bonds, resulting in the formation of products with different properties than the initial substances.

For instance, in the reaction where ammonium nitrite ( \(\mathrm{NH}_{4} \mathrm{NO}_{2}\)) decomposes to produce nitrogen gas and water, we witness a chemical decomposition reaction, a type of chemical reaction wherein a single compound breaks down into two or more products. Familiarizing oneself with such reactions enhances the capability to predict and understand chemical processes.

Stoichiometry is the calculation of reactants and products in chemical reactions. It is derived from the Greek words 'stoicheion' (element) and 'metron' (measure), providing the quantitative relationship between reactants and products in a balanced chemical equation. This concept is fundamental when predicting the outcomes of chemical reactions.

For the correct stoichiometric calculations, one must begin with a balanced chemical equation, as it indicates the ratios in which reactants combine and the amounts of products formed. For example, the balanced decomposition reaction of ammonium nitrite involves one mole of the compound yielding one mole of nitrogen gas and two moles of water, illustrating the stoichiometric relationship.

Reactant quantities determine how much of a product can be formed in a reaction. In chemistry, knowing the limiting reactant—the substance that will be used up first in a chemical reaction, thereby limiting the amount of products that can be formed—is crucial.

For an accurate determination of the limiting reactant, the initial quantities of all reactants must be known. When there is only one reactant, like in the decomposition of ammonium nitrite, the term 'limiting reactant' loses its significance since there is no competition for reaction. Meanwhile, for reactions with multiple reactants, the concept is vital, as it can predict the extent and yield of the reaction. Incorrect or ambiguous statements about limiting reactants, as seen in the exercise examples, highlight the importance of a complete understanding of reactant quantities in stoichiometry.

Especially important is considering all reactants present and performing mole-to-mole comparisons based on the balanced equations. This precise approach allows chemists to predict which reactant will run out first and thus determine the limiting reactant.