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Ch.4 - Chemical Reactions and Chemical Quantities
Chapter 4, Problem 37

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?

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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 branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows us to calculate the amounts of substances consumed and produced in a reaction based on balanced chemical equations. In this case, stoichiometry will help determine how much HBr is needed to react with a given mass of iron and how much hydrogen gas is 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 essential for converting between the mass of a substance and the number of moles, which is crucial in stoichiometric calculations. For this problem, knowing the molar masses of iron (Fe) and hydrobromic acid (HBr) will allow us to find the required mass of HBr and the mass of hydrogen gas produced.
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Balancing Chemical Equations

Balancing chemical equations is the process of ensuring that the number of atoms for each element is the same on both sides of the equation. This reflects the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. The given reaction is already balanced, indicating that two moles of HBr react with one mole of Fe to produce one mole of FeBr2 and one mole of H2, which is crucial for accurate stoichiometric calculations.
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Related Practice
Textbook Question

Balance the equation and calculate how many moles of O2 form when each quantity of reactant completely reacts. N2O5( g) → NO2(g) + O2(g) a. 1.2 mol N2O5

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

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

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?

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

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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