MCAT Chemical and Physical Foundations of Biological Systems Flashcards: 5a Ions In Solutions

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This deck focuses on 5a Ions In Solutions, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Chemical and Physical Foundations of Biological Systems.

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Flashcard 1: Identify the correct expression for ion concentration: $0.15\,\text{M }\text{AlCl}_3$ gives what $[\text{Cl}^-]$?

Answer: $[\text{Cl}^-]=0.45\,\text{M}$. AlCl$_3$ dissociates into three Cl$^-$ ions per unit, tripling the chloride concentration.

Flashcard 2: What is the net ionic equation for precipitation when $ext{AgNO}_3(aq)$ is mixed with $ext{NaCl}(aq)$?

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

Flashcard 3: Which ions are spectator ions when $ext{AgNO}_3(aq)$ reacts with $ext{NaCl}(aq)$?

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

Flashcard 4: What is the solubility rule for all nitrate salts, $$\text{NO}_3^-$, in water?

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

Flashcard 5: What is the definition of an electrolyte in aqueous solution?

Answer: 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.

Flashcard 6: What is the definition of a nonelectrolyte in aqueous solution?

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

Flashcard 7: What is the key distinction between strong and weak electrolytes?

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

Flashcard 8: What is the van 't Hoff factor $i$ for $ext{CaCl}_2$ assuming complete dissociation?

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

Flashcard 9: What is the van 't Hoff factor $i$ for $ext{NaCl}$ assuming complete dissociation?

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

Flashcard 10: What is the van 't Hoff factor $i$ for an ideal nonelectrolyte?

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

Flashcard 11: What is the van 't Hoff factor $i$ for $ext{Al}_2( ext{SO}_4)_3$ assuming complete dissociation?

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

Flashcard 12: State the formula for ionic strength $I$ of a solution in terms of ion concentrations and charges.

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

Flashcard 13: What is the solubility rule for Group $1$ metal salts (e.g., $$\text{Na}^+$, $\text{K}^+$)?

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

Flashcard 14: State the formula for osmotic pressure $$\pi$ of a dilute solution.

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

Flashcard 15: State the freezing point depression formula for an electrolyte solution.

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

Flashcard 16: State the boiling point elevation formula for an electrolyte solution.

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

Flashcard 17: What is the definition of molality $m$?

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

Flashcard 18: What is the definition of molarity $M$?

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

Flashcard 19: Identify whether $ext{BaSO}_4$ is expected to be soluble or insoluble in water by common solubility rules.

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

Flashcard 20: What is the definition of a hydrated ion in water?

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

Flashcard 21: Which way do water molecules orient around a cation in solution?

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

Flashcard 22: Which way do water molecules orient around an anion in solution?

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

Flashcard 23: What is the relationship between ionic charge density and hydration strength?

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

Flashcard 24: Identify the correct expression for ion concentration from a salt: $0.20\,\text{M }\text{CaCl}_2$ gives what $[\text{Cl}^-]$?

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

Flashcard 25: Identify the correct expression for ion concentration: $0.15\,\text{M }\text{AlCl}_3$ gives what $[\text{Al}^{3+}]$?

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