Textbook Problem

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How many ammonium ions and how many sulfate ions are present in a 0.20 mol sample of (NH₄)₂SO₄? How many atoms of N, H, S and O are contained in this sample?

Interpretation Introduction

Interpretation:

For the given sample of ammonium sulfate, the number of moles of ammonium ions and sulfate ions, the numbers of $\text{N, H, S and O}$-atoms are needed to be calculated.

Concept introduction:

Ionic compound are constituted by cations and anions.

• Equation for finding number of atoms from number of moles of a molecule,

$Numberofatoms=numberofmolesofatoms\times 6.022\times {10}^{23}atoms/mol$

Explanation of Solution

The amount of ammonium sulfate is given as $0.20mol$.

Ammonium sulfate is composed of ammonium ion and sulfate ions.

That is, two ammonium ions and one sulfate ion per ammonium sulfate compound.

Therefore,

The number of moles of ammonium ion is $2\times 0.20mol=0.40mol$

The number of moles of ammonium ion is $0.20mol$

Equation for finding number of atoms from number of moles of a molecule,

$Numberofatoms=numberofmolesofatoms\times 6.022\times {10}^{23}atoms/mol$

Therefore,

There are 2nitrogen atoms, 8hydrogen atoms, 1sulfur atom and 4oxygen atoms per ammonium sulfate, so the number of $\text{N, H, S and O}$ atoms in given sample of ammonium sulfate ($0.20mol$) is,

    $NumberofNatoms=0.20mol\times 2\times 6.022\times {10}^{23}atoms/mol=2.4\times {10}^{23}Natoms$

    $NumberofHatoms=0$