Ch.4 - Chemical Quantities & Aqueous Reactions

Problem 32

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Chapter 4, Problem 32

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 15.2 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

Calculate the moles of aluminum (Al) using its molar mass.

Use the stoichiometry of the balanced chemical equation to determine the moles of H2SO4 needed.

Convert the moles of H2SO4 to grams using its molar mass.

Use the stoichiometry of the balanced chemical equation to determine the moles of H2 gas produced.

Convert the moles of H2 gas to grams using its molar mass.

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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.

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.

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 quantified using the ideal gas law if needed. Understanding gas laws helps in predicting the volume or mass of gas produced in a reaction, which is important for determining the amount of hydrogen generated from the complete reaction of aluminum.

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Combined Gas Law

Related Practice

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

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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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 3.2-g pure iron bar on a padlock?

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Open Question

For each of the reactions, calculate the mass (in grams) of the product that forms when 3.67 g of the underlined reactant completely reacts. Assume that there is more than enough of the other reactant. a. Ba(s) + Cl2(g) → BaCl2(s) b. CaO(s) + CO2(g) → CaCO3(s) c. 2 Mg(s) + O2(g) → 2 MgO(s) d. 4 Al(s) + 3 O2(g) → 2 Al2O3(s)

Textbook Question

For each of the reactions, calculate the mass (in grams) of the product that forms when 15.39 g of the underlined reactant completely reacts. Assume that there is more than enough of the other reactant.

a. 2 K(s) + Cl₂(g) → 2 KCl(s)

b. 2 K(s) + Br₂(l) → 2 KBr(s)

c. 4 Cr(s) + 3 O₂(g) → 2 Cr₂O₃(s)

d. 2 Sr(s) + O₂(g) → 2 SrO(s)

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Textbook Question

For each of the acid–base reactions, calculate the mass (in grams) of each acid necessary to completely react with and neutralize 4.85 g of the base. b. 2 HNO₃(aq) + Ca(OH)₂(aq) → 2 H₂O(l) + Ca(NO₃)₂(aq)

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