Calcium carbide, \(\mathrm{CaC}_{2},\) reacts with water to form acetylene. $$\mathrm{CaC}_{2}(s)+2 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{C}_{2} \mathrm{H}_{2}(g)+\mathrm{Ca}(\mathrm{OH})_{2}(s)$$ \begin{equation}\begin{array}{l}{\text { a. How many grams of water are needed to }} \\ {\text { react with } 485 \text { g of calcium carbide? }} \\\ {\text { b. How many grams of } \mathrm{CaC}_{2} \text { could make }} \\\ {\text { 23.6 g } \mathrm{C}_{2} \mathrm{H}_{2} \text { ? }} \\ {\text { c. If } 55.3 \mathrm{g} \mathrm{Ca}(\mathrm{OH})_{2} \text { are formed, how many }} \\ {\text { grams of water reacted? }}\end{array}\end{equation}

Chemical reactions are processes where substances, known as reactants, transform into new substances, called products. In the given exercise, calcium carbide (CaC₂) reacts with water (H₂O) to form acetylene (C₂H₂) and calcium hydroxide (Ca(OH)₂). This particular type of reaction, where a substance reacts with water, is known as a hydrolysis reaction.

To fully understand chemical reactions, students should grasp the concept of conservation of mass, which states that matter is neither created nor destroyed in a chemical reaction. Thus, the amount of each element must be the same in the reactants and products. This leads directly into the importance of balancing chemical equations, a crucial step to Stoichiometry.

Molar mass is a fundamental concept in chemistry that corresponds to the mass of one mole of a substance. It is typically expressed in grams per mole (g/mol). The molar mass is calculated by summing the atomic masses of all the atoms in the molecular formula. Students can find these atomic masses on the periodic table.

For instance, the molar mass of calcium carbide (CaC₂) is found by adding the mass of calcium (Ca) and the mass of two carbon (C) atoms. Understanding molar mass is crucial for converting between grams and moles, which is essential for solving Stoichiometry problems, such as those presented in the original exercise. Accurate molar mass calculations ensure that the stoichiometric conversions between the mass of reactants and products are correct.

Balancing chemical equations is the process of ensuring that the same number of atoms for each element is present on both sides of the equation. This balance honors the Law of Conservation of Mass and is necessary for accurate stoichiometric calculations.

In the exercise, the balanced equation is given. However, students should practice this skill by making sure the number of atoms of each element in the reactants equals those in the products. For example, for every one mole of CaC₂, there should be two moles of H₂O reacting to ensure that all atoms are accounted for in the products. Mastering the art of balancing equations helps students predict the amounts of reactants needed or products formed in a chemical reaction.