Questions: Measurement and Matter Naming ionic compounds with common polyatomic ions Fill in the name and empirical formula of each ionic compound that could be formed from the ions in this table: Some ionic compounds cation anion empirical formula name of compound Mg^2+ OH^- Fe^3+ NO2^- K^+ CN^-

Solution Steps

To find the empirical formula of an ionic compound, balance the total positive and negative charges so that the compound is neutral.

1. For \(\mathrm{Mg}^{2+}\) and \(\mathrm{OH}^{-}\):

   • \(\mathrm{Mg}^{2+}\) has a charge of +2.
   • \(\mathrm{OH}^{-}\) has a charge of -1.
   • To balance the charges, two \(\mathrm{OH}^{-}\) ions are needed for each \(\mathrm{Mg}^{2+}\) ion.
   • Empirical formula: \(\mathrm{Mg(OH)_2}\).

2. For \(\mathrm{Fe}^{3+}\) and \(\mathrm{NO}_2^{-}\):

   • \(\mathrm{Fe}^{3+}\) has a charge of +3.
   • \(\mathrm{NO}_2^{-}\) has a charge of -1.
   • To balance the charges, three \(\mathrm{NO}_2^{-}\) ions are needed for each \(\mathrm{Fe}^{3+}\) ion.
   • Empirical formula: \(\mathrm{Fe(NO_2)_3}\).

3. For \(\mathrm{K}^{+}\) and \(\mathrm{CN}^{-}\):

   • \(\mathrm{K}^{+}\) has a charge of +1.
   • \(\mathrm{CN}^{-}\) has a charge of -1.
   • The charges are already balanced with one of each ion.
   • Empirical formula: \(\mathrm{KCN}\).

The name of an ionic compound is derived from the names of the cation and anion.

1. For \(\mathrm{Mg(OH)_2}\):

   • Cation: Magnesium
   • Anion: Hydroxide
   • Name of compound: Magnesium hydroxide

2. For \(\mathrm{Fe(NO_2)_3}\):

   • Cation: Iron (III) (indicating the +3 charge)
   • Anion: Nitrite
   • Name of compound: Iron (III) nitrite

3. For \(\mathrm{KCN}\):

   • Cation: Potassium
   • Anion: Cyanide
   • Name of compound: Potassium cyanide

Final Answer