Iron(III) oxide reacts with carbon monoxide according to the equation: Fe2O3(s) + 3 CO(g)-2 Fe(s) + 3 CO2(g) A reaction mixture initially contains 22.55 g Fe2O3 and 14.78 g CO. Once the reaction has occurred as completely as possible, what mass (in g) of the excess reactant remains?

Understanding stoichiometry is like having a magical cookbook for chemistry—instead of recipes for cookies, you've got instructions for making new substances from chemical reactions. In chemistry, stoichiometry refers to the relationship between the quantities of reactants and products in a chemical reaction. It's based on the law of conservation of mass, which says that matter is neither created nor destroyed in a reaction. What this means is that the number of atoms of each element must be the same in the reactants and products.

For a stoichiometry calculation, you’ll first need a balanced chemical reaction equation. From this, you can determine the mole ratio of the reactants and products. In the case of our iron(III) oxide and carbon monoxide reaction example, for every 1 mole of Fe₂O₃, 3 moles of CO are required to produce Iron and Carbon dioxide. With this mole ratio, you can actually figure out how much of each reactant you need to completely use up another reactant and how much of each product will form. It all comes down to the power of ratio and proportions—just like doubling or halving your favorite recipe!

Have you ever wondered how chemists measure out atoms when they're too tiny to see? They use the concept of molar mass! Molar mass is sort of like the gram weight of one mole of a chemical, and one mole is Avogadro's number (\(6.022 \times 10^{23}\)) worth of something. You can find molar mass by adding up the atomic masses (from the periodic table) of all the atoms in a chemical formula.

For example, in our problem, iron(III) oxide (Fe₂O₃) has a molar mass calculated by adding twice the atomic mass of iron with three times the atomic mass of oxygen. Knowing the molar mass of the reactants is crucial because it allows us to convert mass in grams (something we can measure) to moles (which is used in stoichiometry calculations). It’s like knowing how many ounces are in a pound when you’re cooking—necessary for getting your quantities right!

A chemical reaction equation is like a detailed script for a molecular-level play. It tells us which molecules are the actors (the reactants), what changes they go through (the reaction), and who leaves the stage transformed (the products). But it's not enough to just list these players; their amounts have to be balanced, just like ensuring there's enough seating for every guest at a dinner party.

The equation for our reaction, iron(III) oxide with carbon monoxide, tells a clear story once balanced: one molecule of Fe₂O₃ reacts with three molecules of CO to produce iron and three molecules of CO₂. It shows that reactions follow specific ratios, which is incredibly important when figuring out how much of each reactant we need and how much of each product we'll get. It’s the blueprint for all stoichiometry calculations and helps predict the outcome of the chemical reaction.

In any good party, it's better to have too much food than not enough—same goes for reactants in a chemical reaction. The reactant that isn’t completely used up is known as the excess reactant. Our chemical reaction can only progress as long as both reactants are present. When one of them runs out, the reaction stops, regardless of how much of the other is left over. That leftover is the excess reactant.

Identifying the limiting reactant (the one that runs out first) and excess reactant tells us a lot about the reaction’s efficiency and allows us to calculate the quantity of leftover reactants. In our scenario, after the limiting reactant (Fe₂O₃) is used up, there’s still some carbon monoxide left—that's our excess reactant. By knowing this, we can calculate how much CO is left after the reaction is completed, which in practical applications can help manage resources and costs effectively.