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Ch.4 - Chemical Reactions and Chemical Quantities
Tro - Chemistry: A Molecular Approach 5th Edition
Tro5th EditionChemistry: A Molecular ApproachISBN: 9780134874371Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoTro 5th EditionCh.4 - Chemical Reactions and Chemical QuantitiesProblema 31a
Capitolo 4, Problema 31a

Hydrobromic acid dissolves solid iron according to the reaction:
Fe(s) + 2 HBr(aq) → FeBr2(aq) + H2(g)
What mass of HBr (in g) do you need to dissolve a 3.2-g pure iron bar on a padlock?

Guida verificata passo dopo passo
1
Identify the balanced chemical equation: \( \text{Fe(s)} + 2 \text{HBr(aq)} \rightarrow \text{FeBr}_2\text{(aq)} + \text{H}_2\text{(g)} \).
Determine the molar mass of iron (Fe) and hydrobromic acid (HBr). The molar mass of Fe is approximately 55.85 g/mol, and the molar mass of HBr is approximately 80.91 g/mol.
Calculate the number of moles of iron in the 3.2 g sample using the formula: \( \text{moles of Fe} = \frac{\text{mass of Fe}}{\text{molar mass of Fe}} \).
Use the stoichiometry of the balanced equation to find the moles of HBr needed. According to the equation, 1 mole of Fe reacts with 2 moles of HBr.
Convert the moles of HBr to grams using the formula: \( \text{mass of HBr} = \text{moles of HBr} \times \text{molar mass of HBr} \).

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Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced equation. It allows us to determine the proportions of substances involved in a reaction. In this case, the stoichiometric coefficients from the balanced equation indicate that 2 moles of HBr are required for every mole of Fe, which is essential for calculating the mass of HBr needed.
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Stoichiometry Concept

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is crucial for converting between the mass of a substance and the number of moles. For this problem, knowing the molar mass of HBr (approximately 80.91 g/mol) and Fe (approximately 55.85 g/mol) will help in determining how much HBr is needed to react with the given mass of iron.
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Chemical Reaction Types

Understanding the type of chemical reaction is important for predicting the products and the behavior of reactants. The reaction between iron and hydrobromic acid is a single displacement reaction, where iron displaces hydrogen from HBr. Recognizing this helps in understanding the overall process and the stoichiometric relationships involved in the reaction.
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Common Types of Alkane Reactions
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Hydrobromic acid dissolves solid iron according to the reaction:

Fe(s) + 2 HBr(aq) → FeBr2(aq) + H2(g)

What mass of HBr (in g) do you need to dissolve a 3.2-g pure iron bar on a padlock? What mass of H2 would the complete reaction of the iron bar produce?

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Consider the balanced equation:

SiO2(s) + 3 C(s) → SiC(s) + 2 CO(g)

Complete the table showing the appropriate number of moles of reactants and products. If the number of moles of a reactant is provided, fill in the required amount of the other reactant, as well as the moles of each product that forms. If the number of moles of a product is provided, fill in the required amount of each reactant to make that amount of product, as well as the amount of the other product that forms.

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