Write equations for the reactions between (a) \(\mathrm{CO}_{2}\) and \(\mathrm{NaOH}(a q),\) (b) \(\mathrm{Na}_{2} \mathrm{O}\) and \(\mathrm{HNO}_{3}(a q)\).

When we talk about chemical reactions, we're referring to the process where substances, known as reactants, transform into new substances, called products. This can involve elements and compounds undergoing changes in their molecular structures through various types of reactions such as synthesis, decomposition, single replacement, or double replacement.

In the textbook exercise discussed, we are dealing with one synthesis reaction where sodium hydroxide combines with carbon dioxide, and one double replacement reaction involving the interaction of sodium oxide with nitric acid. The ability to predict and write chemical equations for such reactions is a foundational skill in chemistry that allows us to understand and anticipate the results of combining different chemicals.

Stoichiometry is essentially the math behind chemistry. It involves calculating the relative quantities of reactants and products during chemical reactions, ensuring that the Law of Conservation of Mass is followed. This law states that in a closed system, mass is conserved and cannot be created or destroyed.

For instance, in the given exercise solutions, we see stoichiometry at play when we balance chemical equations. Balancing these equations is like solving a puzzle where every atom that enters a reaction must also exit within the products. The balanced equations from the exercise—CO2 + 2NaOH -> Na2CO3 + H2O and Na2O + 2HNO3 -> 2NaNO3 + H2O—illustrate how stoichiometric coefficients are used to ensure the number of atoms for each element is equal on both sides of the reaction.

Predicting the products of a chemical reaction requires an understanding of how different substances interact. This is not purely guesswork; rather, it is based on established rules of how certain compounds behave when combined.

For example, acids typically react with bases to produce salts and water—a reaction type known as neutralization. In part (b) of the exercise, nitric acid reacts with sodium oxide, following this pattern of acid-base reaction. Knowing such patterns, recognizing compound types, and understanding reactivity trends are all part of the skill set needed for predicting the products in chemical reactions. Through practice, students become more adept at foreseeing how various reactant combinations will play out.