Ions in Solutions (5A) - MCAT Chemical and Physical Foundations of Biological Systems

$\text{Ag}^+(aq)+\text{Cl}^-(aq)\rightarrow\text{AgCl}(s)$. The net ionic equation shows only the species that form the precipitate, excluding spectators.

$\text{Na}^+$ and $\text{NO}_3^-$. Spectator ions do not participate in the reaction, remaining unchanged in solution.

All nitrates are soluble in water. Nitrate ions form soluble compounds with most cations due to their high hydration energy.

A solute that produces ions in water and conducts electricity. Electrolytes ionize in water, enabling the flow of electric current through the movement of charged particles.

A solute that does not produce ions in water; no conductivity. Nonelectrolytes remain molecular in solution, preventing ion formation and thus electrical conduction.

Strong: ~complete dissociation; weak: partial dissociation. Strong electrolytes fully ionize into ions, while weak ones establish an equilibrium with partial ionization.

$i=3$. CaCl$_2$ dissociates into three ions: one Ca$^{2+}$ and two Cl$^-$, for colligative calculations.

$i=2$. NaCl dissociates into two ions, Na$^+$ and Cl$^-$, affecting colligative properties accordingly.

$i=1$. Nonelectrolytes do not dissociate, contributing only one particle per molecule in colligative properties.

$i=5$. Al$_2$(SO$_4$)$_3$ produces five ions: two Al$^{3+}$ and three SO$_4^{2-}$, in complete dissociation.

$I=\frac{1}{2}\sum c_i z_i^2$. Ionic strength quantifies the total concentration of ions, weighted by the square of their charges.

All Group $1$ salts are soluble in water. Group 1 cations form highly soluble salts due to their low charge density and high hydration.

$\pi=iMRT$. Osmotic pressure accounts for the van 't Hoff factor to include effects of ionic dissociation in dilute solutions.

$\Delta T_f=iK_f m$. Freezing point depression incorporates the van 't Hoff factor to reflect the number of particles from electrolytes.

$\Delta T_b=iK_b m$. Boiling point elevation uses the van 't Hoff factor for the effective particle concentration from dissociation.

Moles solute per kilogram of solvent. Molality expresses concentration independent of temperature, focusing on solvent mass for colligative properties.

Moles solute per liter of solution. Molarity measures solute concentration per volume of solution, useful for stoichiometric calculations.

Insoluble. BaSO$_4$ has low solubility due to strong lattice energy exceeding hydration energy.

An ion surrounded by oriented water molecules (hydration shell). Ions in water attract polar water molecules, forming a structured layer due to electrostatic interactions.

Oxygen ends point toward the cation. Water's dipole orients with the negative oxygen toward positive cations for electrostatic stabilization.

Hydrogen ends point toward the anion. Water dipoles align with positive hydrogens facing negative anions to minimize energy in the hydration shell.

Higher charge density implies stronger hydration. Ions with higher charge per volume attract water more strongly, enhancing solvation energy.

$[\text{Cl}^-]=0.40,\text{M}$. CaCl$_2$ dissociates to release two Cl$^-$ ions per formula unit, doubling the chloride concentration.

$[\text{Al}^{3+}]=0.15,\text{M}$. AlCl$_3$ provides one Al$^{3+}$ ion per molecule, matching the salt's molar concentration.