Question

Determine the number of moles of each type of monatomic or polyatomic ion in one mole of the following compounds. For each polyatomic ion, determine the number of moles of each atom present in one mole of the ion. a. \({KNO}_{3}\) b. \({Na}_{2} {SO}_{4}\) c. \({Ca}({OH})_{2}\) d. \(({NH}_{4})_{2} {SO}_{3}\) e. \({Ca}_{3}({PO}_{4})_{2}\) f. \({Al}_{2}({CrO}_{4})_{3}\)

Short answer

a) 1 K, 1 N, 3 O. b) 2 Na, 1 S, 4 O. c) 1 Ca, 2 O, 2 H. d) 2 N, 8 H, 1 S, 3 O. e) 3 Ca, 2 P, 8 O. f) 2 Al, 3 Cr, 12 O.

Step-by-step solution

- Identify the Ions in Each Compound

Break down each compound into its constituent ions. For example, identify the cations and anions in each formula.

- Determine the Number of Each Ion in the Compound

Count how many of each type of ion are present in one formula unit of the compound.

- Assign Moles to Each Ion

Since each compound has 1 mole, assign the counted ions from step 2 to the number of moles.

- Determine the Number of Atoms in Polyatomic Ions

For polyatomic ions, further break down the ion into its constituent atoms to determine the number of moles of each atom present in 1 mole of the ion.

Solution for Part a - \( KNO_{3} \)

KNO₃ contains 1 K⁺ ion and 1 NO₃⁻ ion.- For 1 mole of KNO₃: 1 mole K⁺, 1 mole NO₃⁻.- Breaking down NO₃⁻: 1 N atom, 3 O atoms per NO₃⁻ ion, so 1 mole NO₃⁻ gives 1 mole N and 3 moles O.

Solution for Part b - \( Na_{2}SO_{4} \)

Na₂SO₄ contains 2 Na⁺ ions and 1 SO₄²⁻ ion.- For 1 mole of Na₂SO₄: 2 moles Na⁺, 1 mole SO₄²⁻.- Breaking down SO₄²⁻: 1 S atom, 4 O atoms per SO₄²⁻ ion, so 1 mole SO₄²⁻ gives 1 mole S and 4 moles O.

Solution for Part c - \( Ca(OH)_{2} \)

Ca(OH)₂ contains 1 Ca²⁺ ion and 2 OH⁻ ions.- For 1 mole of Ca(OH)₂: 1 mole Ca²⁺, 2 moles OH⁻.- Breaking down OH⁻: each OH⁻ has 1 O atom and 1 H atom, so 2 moles OH⁻ gives 2 moles O and 2 moles H.

Solution for Part d - \( (NH_{4})_{2}SO_{3} \)

(NH₄)₂SO₃ contains 2 NH₄⁺ ions and 1 SO₃²⁻ ion.- For 1 mole of (NH₄)₂SO₃: 2 moles NH₄⁺, 1 mole SO₃²⁻.- Breaking down NH₄⁺: each NH₄⁺ has 1 N atom and 4 H atoms, so 2 moles NH₄⁺ gives 2 moles N and 8 moles H.- Breaking down SO₃²⁻: 1 S atom and 3 O atoms per SO₃²⁻ ion, so 1 mole SO₃²⁻ gives 1 mole S and 3 moles O.

Solution for Part e - \( Ca_{3}(PO_{4})_{2} \)

Ca₃(PO₄)₂ contains 3 Ca²⁺ ions and 2 PO₄³⁻ ions.- For 1 mole of Ca₃(PO₄)₂: 3 moles Ca²⁺, 2 moles PO₄³⁻.- Breaking down PO₄³⁻: each PO₄³⁻ has 1 P atom and 4 O atoms, so 2 moles PO₄³⁻ gives 2 moles P and 8 moles O.

Solution for Part f - \( Al_{2}(CrO_{4})_{3} \)

Al₂(CrO₄)₃ contains 2 Al³⁺ ions and 3 CrO₄²⁻ ions.- For 1 mole of Al₂(CrO₄)₃: 2 moles Al³⁺, 3 moles CrO₄²⁻.- Breaking down CrO₄²⁻: each CrO₄²⁻ has 1 Cr atom and 4 O atoms, so 3 moles CrO₄²⁻ gives 3 moles Cr and 12 moles O.

Key concepts

mole calculation

Understanding mole calculations is fundamental in chemistry. A mole represents a quantity (6.022 x 10²³ entities) of atoms, molecules, or ions. To convert between moles and the number of these entities, use Avogadro's number. For instance, if you have 1 mole of \( NaCl \), you have 1 mole of Na⁺ ions and 1 mole of Cl⁻ ions because each formula unit of \( NaCl \) contains one Na and one Cl ion. Hence, comprehending the chemical formula lets you determine the number of moles of each component based on the compound composition.

ions in compounds

Compounds often consist of ions that are held together by ionic bonds. Recognizing the constituent ions in a compound is crucial. For example, in \( KNO_3 \), there are K⁺ and NO₃⁻ ions. Each ion in the compound retains its identity. To find the moles of each ion, count the number of ions per formula unit. For \( Ca(OH)_2 \), it contains 1 Ca²⁺ ion and 2 OH⁻ ions. Interpreting the chemical formula helps you understand that for each mole of \( Ca(OH)_2 \), there is one mole of Ca²⁺ ions and two moles of OH⁻ ions.

polyatomic ions

Polyatomic ions are charged species composed of two or more atoms covalently bonded. Common examples include sulfate (SO₄²⁻), nitrate (NO₃⁻), and ammonium (NH₄⁺). When analyzing compounds with polyatomic ions, note how many of these ions are present. For instance, \( Na_2SO_4 \) contains 2 Na⁺ ions and 1 SO₄²⁻ ion. Break down the polyatomic ion into individual atoms to determine how many moles of each atom are present. For example, 1 mole of SO₄²⁻ yields 1 mole of S atoms and 4 moles of O atoms.

chemical formula interpretation

Interpreting chemical formulas allows you to discern the number of different ions and atoms in a compound. The subscript in the formula indicates the number of each type of ion or atom. For example, in \( (NH_4)_2SO_3 \), the subscript '2' after \( NH_4 \) denotes that there are 2 NH₄⁺ ions per formula unit. To break it down: 2 moles of NH₄⁺ contain 2 moles of N and 8 moles of H. Similarly, interpreting \( Al_2(CrO_4)_3 \) shows that there are 2 Al³⁺ ions and 3 CrO₄²⁻ ions, composing full knowledge of the compound's structure.