Question

Specify what ions are present upon dissolving each of the following substances in water: (a) ${\mathrm{MgI}}_2$, (b) $\mathrm{Al}{\left({\mathrm{NO}}_3\right)}_3,$ (c) ${\mathrm{HClO}}_4$, (d) ${\mathrm{NaCH}}_3\mathrm{COO}$

Short answer

Upon dissolving the given substances in water, the following ions are present: (a) ${\mathrm{MgI}}_2$: Magnesium ions (${\mathrm{Mg}}^{2+}$) and iodide ions (I⁻) (b) $\mathrm{Al}{\left({\mathrm{NO}}_3\right)}_3$: Aluminum ions (${\mathrm{Al}}^{3+}$) and nitrate ions (NO₃⁻) (c) ${\mathrm{HClO}}_4$: Hydrogen ions (${\mathrm{H}}^{+}$) and perchlorate ions (ClO₄⁻) (d) ${\mathrm{NaCH}}_3\mathrm{COO}$: Sodium ions (${\mathrm{Na}}^{+}$) and acetate ions (CH₃COO⁻)

Step-by-step solution

(a) Dissociating MgI₂

When magnesium iodide (${\mathrm{MgI}}_2$) is dissolved in water, it dissociates into one magnesium ion (Mg²⁺) and two iodide ions (I⁻): $${\mathrm{MgI}}_2\to {\mathrm{Mg}}^{2+}+2{\mathrm{I}}^{-}$$

Ions Present in MgI₂ Solution

In the case of a ${\mathrm{MgI}}_2$ solution, we have magnesium ions (${\mathrm{Mg}}^{2+}$) and iodide ions (I⁻). -----

(b) Dissociating Al(NO₃)₃

When aluminum nitrate ($\mathrm{Al}{\left({\mathrm{NO}}_3\right)}_3$) is dissolved in water, it dissociates into one aluminum ion (Al³⁺) and three nitrate ions (NO₃⁻): $$\mathrm{Al}{\left({\mathrm{NO}}_3\right)}_3\to {\mathrm{Al}}^{3+}+3{\mathrm{NO}}_3^{-}$$

Ions Present in Al(NO₃)₃ Solution

In the case of an $\mathrm{Al}{\left({\mathrm{NO}}_3\right)}_3$ solution, we have aluminum ions (${\mathrm{Al}}^{3+}$) and nitrate ions (NO₃⁻). -----

(c) Dissociating HClO₄

When perchloric acid (${\mathrm{HClO}}_4$) is dissolved in water, it dissociates into one hydrogen ion (H⁺) and one perchlorate ion (ClO₄⁻): $${\mathrm{HClO}}_4\to {\mathrm{H}}^{+}+{\mathrm{ClO}}_4^{-}$$

Ions Present in HClO₄ Solution

In the case of an ${\mathrm{HClO}}_4$ solution, we have hydrogen ions (${\mathrm{H}}^{+}$) and perchlorate ions (ClO₄⁻). -----

(d) Dissociating NaCH₃COO

When sodium acetate (${\mathrm{NaCH}}_3\mathrm{COO}$) is dissolved in water, it dissociates into one sodium ion (Na⁺) and one acetate ion (CH₃COO⁻): $${\mathrm{NaCH}}_3\mathrm{COO}\to {\mathrm{Na}}^{+}+{\mathrm{CH}}_3{\mathrm{COO}}^{-}$$

Ions Present in NaCH₃COO Solution

In the case of a ${\mathrm{NaCH}}_3\mathrm{COO}$ solution, we have sodium ions (${\mathrm{Na}}^{+}$) and acetate ions (CH₃COO⁻).

Key concepts

Dissociation

When ionic compounds dissolve in water, they undergo a process called dissociation. This means that the compound separates into its individual ions. For example, when magnesium iodide (${\mathrm{MgI}}_2$) is placed in water, it breaks up into one magnesium ion (${\mathrm{Mg}}^{2+}$) and two iodide ions (${\mathrm{I}}^{-}$).
Dissociation happens because water molecules, which are polar, interact with the ions. The positive end of the water molecule attracts the negatively charged ion, and the negative end attracts the positively charged ion. This interaction helps to pull the ions apart from each other, allowing them to move freely in the solution.
Understanding dissociation is crucial because it explains why ionic compounds can conduct electricity when dissolved in water. **Solutions with dissociated ions are essential in many chemical processes and reactions.**

• Initiates when ionic compounds are solvated by water molecules.
• Increases the mobility of ions in a solution.
• Essential for the electrical conductivity of solutions.

Aqueous Solutions

An aqueous solution is formed when a substance is dissolved in water. **Water is a universal solvent** and can dissolve a wide range of substances due to its polar nature. **This makes it an excellent medium for chemical reactions,** especially those involving ionic compounds.
In the context of ionic compounds, their dissociation in water results in an aqueous solution containing free-moving ions. For instance, aluminum nitrate ($\mathrm{Al}{\left({\mathrm{NO}}_3\right)}_3$) dissolves in water to produce aluminum ions (${\mathrm{Al}}^{3+}$) and nitrate ions (${\mathrm{NO}}_3^{-}$). This solution is termed 'aqueous' because the solvent is water.
Aqueous solutions are particularly important in daily life and industrial applications. They are used in **fields such as medicine, agriculture, and food processing.**

• Solvent is typically water.
• Allows ions to move freely, facilitating chemical reactions.
• Used extensively in various industrial and laboratory processes.

Ions in Solution

Ions present in aqueous solutions are charged particles that result from the dissociation of ionic compounds. When sodium acetate (${\mathrm{NaCH}}_3\mathrm{COO}$) dissolves, it breaks into sodium ions (${\mathrm{Na}}^{+}$) and acetate ions (${\mathrm{CH}}_3{\mathrm{COO}}^{-}$). These ions can move freely in the solution.
This characteristic of ions in solution is what allows the solution to conduct electricity. The movement of charged particles (ions) facilitates the flow of electric current. Thus, solutions with a higher concentration of ions have better conductivity.
Additionally, ions in solution participate in chemical reactions. They can recombine to form new compounds, interact with other ions or molecules, and play critical roles in biological systems such as nerve impulse transmission and muscle contraction.

• Free-moving charged particles in a solution.
• Enable electrical conductivity in solutions.
• Participate in various chemical and biological processes.