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Ch.3 - Mass Relationships in Chemical Reactions
Chapter 3, Problem 62

In the preparation of iron from hematite, Fe2O3 reacts with carbon: Fe2O3 + C --> Fe + CO2 Unbalanced (a) Balance the equation. (b) How many moles of carbon are needed to react with 525 g of hematite? (c) How many grams of carbon are needed to react with 525 g of hematite?

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Step 1: Balance the chemical equation. Start by balancing the number of iron (Fe) atoms. Since there are 2 Fe atoms in Fe2O3, you need 2 Fe atoms on the product side. The balanced equation is: Fe2O3 + 3C → 2Fe + 3CO2.
Step 2: Calculate the molar mass of Fe2O3. Use the atomic masses: Fe = 55.85 g/mol and O = 16.00 g/mol. The molar mass of Fe2O3 is (2 * 55.85) + (3 * 16.00) g/mol.
Step 3: Convert 525 g of Fe2O3 to moles using its molar mass. Use the formula: moles = mass (g) / molar mass (g/mol).
Step 4: Use the stoichiometry of the balanced equation to find the moles of carbon needed. According to the balanced equation, 1 mole of Fe2O3 reacts with 3 moles of C.
Step 5: Convert the moles of carbon to grams. Use the molar mass of carbon (C = 12.01 g/mol) and the formula: mass (g) = moles * molar mass (g/mol).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Balancing Chemical Equations

Balancing chemical equations involves ensuring that the number of atoms of each element is the same on both sides of the equation. This is based on the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. To balance an equation, coefficients are adjusted in front of the chemical formulas to achieve equal atom counts.
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Molar Mass and Moles

The molar mass of a substance is the mass of one mole of that substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a molecule. Understanding moles is crucial for stoichiometric calculations, as it allows for the conversion between grams and the number of particles, facilitating the determination of reactant and product quantities in a reaction.
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Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It uses balanced equations to determine how much of each substance is needed or produced. By applying stoichiometric principles, one can calculate the required amounts of reactants, such as carbon in this case, based on the mass of the starting material, hematite.
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