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Ch.4 - Chemical Reactions and Chemical Quantities
Tro - Chemistry: A Molecular Approach 6th Edition
Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217Not the one you use?Change textbook
All textbooksTro 6th EditionCh.4 - Chemical Reactions and Chemical QuantitiesProblem 38
Chapter 4, Problem 38

Sulfuric acid dissolves aluminum metal according to the reaction:
2 Al(s) + 3 H2SO4(aq) → Al2(SO4)3(aq) + 3 H2(g)
Suppose you want to dissolve an aluminum block with a mass of 11.3 g. What minimum mass of H2SO4 (in g) do you need? What mass of H2 gas (in g) does the complete reaction of the aluminum block produce?

Verified step by step guidance
1
Calculate the moles of aluminum (Al) using its molar mass: \( \text{Molar mass of Al} = 26.98 \, \text{g/mol} \). Use the formula: \( \text{moles of Al} = \frac{\text{mass of Al}}{\text{molar mass of Al}} \).
Use the stoichiometry of the balanced chemical equation to find the moles of \( \text{H}_2\text{SO}_4 \) needed. According to the equation, 2 moles of Al react with 3 moles of \( \text{H}_2\text{SO}_4 \).
Calculate the mass of \( \text{H}_2\text{SO}_4 \) required using its molar mass: \( \text{Molar mass of H}_2\text{SO}_4 = 98.08 \, \text{g/mol} \). Use the formula: \( \text{mass of H}_2\text{SO}_4 = \text{moles of H}_2\text{SO}_4 \times \text{molar mass of H}_2\text{SO}_4} \).
Determine the moles of \( \text{H}_2 \) gas produced using the stoichiometry of the reaction. From the balanced equation, 2 moles of Al produce 3 moles of \( \text{H}_2 \).
Calculate the mass of \( \text{H}_2 \) gas using its molar mass: \( \text{Molar mass of H}_2 = 2.02 \, \text{g/mol} \). Use the formula: \( \text{mass of H}_2 = \text{moles of H}_2 \times \text{molar mass of H}_2} \).

Key Concepts

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

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical 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 the molar ratios of aluminum to sulfuric acid and hydrogen gas, which are essential for calculating the required mass of sulfuric acid and the mass of hydrogen produced.
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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, which is necessary for stoichiometric calculations. For aluminum (Al) and sulfuric acid (H2SO4), knowing their molar masses allows us to calculate how much sulfuric acid is needed to react with a given mass of aluminum.
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Gas Laws

Gas laws describe the behavior of gases under various conditions of temperature and pressure. In this context, the production of hydrogen gas (H2) from the reaction can be analyzed using the ideal gas law if needed. Understanding gas laws helps in predicting the volume of gas produced and its behavior, although in this case, we focus on the mass of hydrogen generated from the stoichiometric calculations.
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Related Practice
Textbook Question

Find the limiting reactant for each initial amount of reactants. 4 Al(s) + 3 O2( g) → 2 Al2O3(s)

a. 4 mol Al, 2 mol O2

b. 5 mol Al, 3 mol O2

c. 17 mol Al, 11 mol O2

d. 8.8 mol Al, 7.2 mol O2

Textbook Question

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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Textbook Question

Find the limiting reactant for each initial amount of reactants. 2 Na(s) + Br2( g) → 2 NaBr(s) c. 1.5 mol Na, 2.1 mol Br2

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Textbook Question

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 2.80-g pure iron bar on a padlock? What mass of H2 would the complete reaction of the iron bar produce?

Textbook Question

Balance the equation and calculate how many moles of N2 form when each quantity of reactant completely reacts. N2H4(l) → NH3(g) + N2(g) c. 33.9 g N2H4

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