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Ch.7 Chemical Quantities and Reactions
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
All textbooksTimberlake 13th EditionCh.7 Chemical Quantities and ReactionsProblem 114c
Chapter 7, Problem 114c

Ammonium sulfate, (NH4)2SO4, is used in fertilizers to provide nitrogen for the soil.
c. How many moles of ammonium sulfate contain 7.4 × 1025 atoms of N?

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1
Step 1: Begin by identifying the chemical formula of ammonium sulfate, (NH₄)₂SO₄. This compound contains two ammonium ions (NH₄⁺), each of which has one nitrogen atom. Therefore, there are 2 nitrogen atoms per formula unit of ammonium sulfate.
Step 2: Determine the relationship between the number of nitrogen atoms and the number of ammonium sulfate formula units. Since each formula unit contains 2 nitrogen atoms, the total number of nitrogen atoms is twice the number of formula units.
Step 3: Use Avogadro's number (6.022 × 10²³ atoms/mol) to relate the number of formula units to moles. Divide the given number of nitrogen atoms (7.4 × 10²⁵ atoms) by 2 to find the number of ammonium sulfate formula units, and then divide this result by Avogadro's number to convert formula units to moles.
Step 4: Write the mathematical expression for the calculation: \[ \text{Moles of ammonium sulfate} = \frac{\text{Number of nitrogen atoms}}{2 \times 6.022 \times 10^{23}} \].
Step 5: Perform the calculation using the provided values to determine the number of moles of ammonium sulfate. Ensure units are consistent throughout the calculation.

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Key Concepts

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

Moles and Avogadro's Number

A mole is a unit in chemistry that represents 6.022 x 10²³ entities, such as atoms or molecules. This number, known as Avogadro's number, allows chemists to convert between the mass of a substance and the number of particles it contains. Understanding moles is essential for calculating the number of moles from a given number of atoms.
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Chemical Composition of Ammonium Sulfate

Ammonium sulfate, (NH₄)₂SO₄, consists of two ammonium ions (NH₄⁺) and one sulfate ion (SO₄²⁻). Each ammonium ion contains one nitrogen atom, meaning that one formula unit of ammonium sulfate contains two nitrogen atoms. Knowing the chemical composition is crucial for determining how many moles of ammonium sulfate correspond to a specific number of nitrogen atoms.
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Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It allows for the calculation of the amounts of substances involved based on their chemical formulas. In this context, stoichiometry helps in determining how many moles of ammonium sulfate are needed to yield a certain number of nitrogen atoms.
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Related Practice
Textbook Question

Ammonium sulfate, (NH4)2SO4, is used in fertilizers to provide nitrogen for the soil.

b. How many H atoms are in 0.100 mole of ammonium sulfate?

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Textbook Question

Ammonium sulfate, (NH4)2SO4, is used in fertilizers to provide nitrogen for the soil.

a. How many formula units are in 0.200 mole of ammonium sulfate?

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Textbook Question

Consider the following unbalanced equation:

Al(s) + O2(g) → Al2O3(s)

b. Identify the type of reaction.