Hydrogen gas is bubbled into a solution of barium hydroxide that has sulfur in it. The unbalanced equation for the reaction that takes place is $$ \mathrm{H}_{2}(g)+\mathrm{S}(s)+\mathrm{OH}^{-}(a q) \longrightarrow \mathrm{S}^{2-}(a q)+\mathrm{H}_{2} \mathrm{O} $$ (a) Balance the equation. (b) What volume of \(0.349 \mathrm{M} \mathrm{Ba}(\mathrm{OH})_{2}\) is required to react completely with \(3.00 \mathrm{~g}\) of sulfur?

Stoichiometry is the area of chemistry that pertains to the quantitative relationship between reactants and products in a chemical reaction. It requires a balanced chemical equation to determine the proportions of reactants needed to form a certain amount of product, or vice versa. For example, in the reaction of hydrogen gas with sulfur and hydroxide to produce sulfide ions and water, the stoichiometric coefficients tell us that one mole of hydrogen reacts with one mole of sulfur and two moles of hydroxide ions to produce one mole of sulfide and two moles of water. Understanding stoichiometry is critical because it ensures that reactions occur with the right amounts of substances, leading to the desired yield without unnecessary waste of chemicals.

An important advice to improve the exercise understanding is to ensure the balanced reaction is clearly laid out. For students, visualizing the atoms of each element on both sides of the chemical equation helps them fully comprehend the balancing process. Drawing a table or chart that lists each element and its atom count on both the reactant and product sides can be beneficial.

Molar mass is a fundamental concept in chemistry that reflects the mass of one mole of a substance, typically measured in grams per mole (g/mol). It can easily be calculated by summing the atomic masses of all atoms in a chemical formula. For instance, sulfur's atomic mass is roughly 32.07 g/mol, meaning one mole of sulfur weighs 32.07 grams. To find out how many moles a certain mass of a substance represents, you divide the mass by the molar mass.

This calculation is essential when dealing with chemical reactions, as it allows us to convert mass into moles, a necessary step in stoichiometry. It's beneficial for students to practice converting between mass and moles using the formula: \[ \text{moles} = \frac{\text{mass}}{\text{molar mass}} \]. This strengthens their understanding of how the mass of a substance relates to the number of particles it contains. Remember that rounding atomic masses to two decimal places is usually sufficient for most calculations, but precision may be crucial for more complex exercises.

Molarity, often denoted as 'M,' is a measure of concentration that represents the number of moles of a solute in one liter of solution. Understanding the relationship between molarity, volume, and moles is essential for dilution and mixing solutions. The formula expressing this relationship is: \[ M = \frac{\text{moles of solute}}{\text{volume of solution in liters}} \].

When working to find the volume of a Ba(OH)₂ solution needed to react with sulfur, students can rearrange the molarity equation to solve for volume given the molarity and the moles of solute. The equation becomes \[\text{volume} = \frac{\text{moles of solute}}{\text{Molarity}}\]. By integrating this understanding, students can calculate how much of a reactant is required in a reaction or how to make solutions of desired concentrations. Highlighting this concept with different examples where volumes and concentrations are altered can demonstrate the versatility of this relationship. Adding exercises that require conversion between liters and milliliters is also advisable, as this is a common task in laboratory settings.