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Chemical equation balancing is a crucial step in understanding how substances react with each other. It involves ensuring that the number of atoms for each element is the same on both sides of the equation. This represents the conservation of mass principle, which dictates that matter cannot be created or destroyed in a chemical reaction.
For the formation of iron sulfide (FeS), the reaction can be represented by:

• \[\text{Fe} + \text{S} \rightarrow \text{FeS}\]

In this equation, each side has one iron (Fe) atom and one sulfur (S) atom, making it already balanced.
This equilibrium is important because it allows us to accurately predict the amount of product produced given the amounts of reactants used. Balancing equations is foundational in chemical calculations, such as finding limiting reactants or calculating theoretical yields.

Molar mass allows chemists to convert between a substance's mass and the moles present, which is pivotal when solving chemical equations. Molar mass is the mass of one mole of a substance and is expressed in grams per mole (g/mol).
To calculate the molar mass of

• Iron (Fe): Refer to the periodic table and find that Fe has a molar mass of approximately 55.85 g/mol.
• Sulfur (S): Similarly, the molar mass is 32.07 g/mol.
• Iron sulfide (FeS): Add the molar masses of iron and sulfur: 55.85 g/mol + 32.07 g/mol, resulting in 87.92 g/mol.

These values are essential for determining the number of moles of each reactant and product, providing a quantitative basis for reaction stoichiometry. Knowing the molar mass helps in calculations involving limiting reactants and theoretical yields.

Theoretical yield refers to the maximum amount of product that can be formed from a given amount of reactants, assuming complete reaction under ideal conditions. It's calculated by using the balanced equation and involves finding the limiting reactant first.
The steps to calculate the theoretical yield are:

• Identify the reactant that will run out first, known as the limiting reactant. Compare the number of moles of each reactant to determine this.
• Use the balanced equation to determine how many moles of product each mole of the limiting reactant produces. In the reaction \(\text{Fe} + \text{S} \rightarrow \text{FeS},\)

1 mole of Fe reacts with 1 mole of S to produce 1 mole of FeS.

• Calculate the theoretical mass of FeS that can be produced by multiplying moles of the limiting reactant by the molar mass of FeS, which we found to be 87.92 g/mol.

The theoretical yield helps predict whether the amount of product will be equal to, less than, or more than the combined masses of reactants used. In this scenario, the result will always be less due to the limiting reactant principle.