Aqueous Solutions, Solubility, and Ionic Equations

Comprehensive practice flashcards covering homogeneous and heterogeneous solutions, electrolytes, dissociation versus ionization, writing net ionic equations, major entity determination, and solubility curve interpretation.

How do homogeneous mixtures (solutions) differ in appearance and composition from heterogeneous mixtures?

Homogeneous mixtures have the same composition throughout, are evenly dispersed, and appear clear and colorless. Heterogeneous mixtures have different compositions throughout and appear opaque or cloudy.

What roles do the solute and solvent play in a solution?

The solute is the substance that is dissolved (e.g., salt), whereas the solvent is the substance that does the dissolving (e.g., water).

What is the difference between electrolytes and non-electrolytes in aqueous solution?

Electrolytes are soluble compounds whose aqueous solutions conduct electricity (e.g., salt water). Non-electrolytes are soluble compounds whose aqueous solutions do not conduct electricity (e.g., alcohol).

What is dissociation, and what happens at the molecular level when an ionic compound dissociates in water?

Dissociation is the separation of ions that occurs when an ionic compound dissolves in water. Ions are separated by water molecules, unable to attract back into a crystal lattice shape, and are free to move around.

Why does a solution with complete dissociation have higher electrical conductivity than one with partial dissociation?

Complete dissociation produces a higher concentration of free ions in solution (e.g., $Na_2SO_4(s) \rightarrow 2Na^+(aq) + SO_4^{2-}(aq)$), whereas partial dissociation (e.g., $PbCl_2(s) \rightleftharpoons Pb^{2+}(aq) + 2Cl^-(aq)$) has fewer ions moving in solution.

What general rule explains why molecular compounds like gasoline ($C_8H_{18}(l)$) do not dissolve in water?

The rule is 'like dissolves like'. Gasoline is non-polar and cannot dissolve in polar water; instead, separation occurs due to differences in density.

What occurs during the process of ionization for an acid?

Ionization occurs when a molecular solute reacts with $H_2O$ to form ions in solution, releasing a hydrogen ion ($H^+(aq)$) and a balancing species.

How do strong acids and weak acids differ in their extent of ionization and equation notation?

Only the $6$ strongest acids ionize $100\%$, represented by a single forward arrow ($\rightarrow$). Weak acids ionize $< 50\%$, represented by an equilibrium arrow ($\rightleftharpoons$). When ionizing, acids lose only $1\,H^+(aq)$ per reaction step.

How are saturated, unsaturated, and supersaturated solutions defined?

A saturated solution contains the maximum concentration of dissolved solute and cannot dissolve more unless temperature changes. An unsaturated solution has not reached maximum concentration and can dissolve more. A supersaturated solution contains more dissolved solute than it can normally hold.

What is the difference between miscible and immiscible liquids?

Miscible liquids dissolve in any proportion with no maximum limit. Immiscible liquids do not dissolve in each other and separate due to density differences.

How do temperature and pressure affect the solubility of solids compared to gases in liquid solvents?

For solids, increasing temperature increases solubility (uses energy), while pressure does not affect it. For gases, increasing temperature decreases solubility (an indirect relationship), while increasing pressure increases solubility.

What are the three types of chemical equations used to represent reactions in aqueous solution?

1. Non-ionic equation: All reactants and products are written as intact neutral compounds with state symbols included. 2. Total ionic equation: All soluble raw substances are separated into their actual dissociated ions. 3. Net ionic equation: Spectator ions (ions that do not change state or charge) are eliminated, leaving only the reacting species.

What is the net ionic equation when aqueous silver nitrate is mixed with aqueous sodium chloride?

$$Ag^+(aq) + Cl^-(aq) \rightarrow AgCl(s)$$

What are the major entities present in an aqueous solution of a high-solubility ionic compound versus a low-solubility ionic compound?

A high-solubility ionic compound (e.g., $NaCl(s)$) exists primarily as separate ions and water: $Na^+(aq)$, $Cl^-(aq)$, and $H_2O(l)$. A low-solubility ionic compound (e.g., $CaCO_3(s)$) exists primarily as the intact compound and water: $CaCO_3(s)$ and $H_2O(l)$.

What are the major entities present in an aqueous solution of a strong acid compared to a weak acid?

A strong acid (e.g., $HCl(l)$) exists as positive hydrogen ions, its negative ions, and water: $H^+(aq)$, $Cl^-(aq)$, and $H_2O(l)$. A weak acid (e.g., $CH_3COOH(l)$) exists predominantly as the intact aqueous molecule and water: $CH_3COOH(aq)$ and $H_2O(l)$.

What are the major entities present in an aqueous solution containing ammonia ($NH_3(g)$) and aluminum metal ($Al(s)$) respectively?

For ammonia: $NH_3(aq)$ and $H_2O(l)$. For aluminum metal: $Al(s)$ and $H_2O(l)$.

In the potassium nitrate ($KNO_3$) solubility investigation, what formula is used to calculate solubility per $100\,\text{mL}$ of water?

$$\frac{\text{solubility}}{100\,\text{mL}} = \frac{14.0\,\text{g}}{\text{your volume}}$$

According to experimental solubility data, what is the solubility of potassium nitrate at $60\,^\circ\text{C}$ and at $90\,^\circ\text{C}$?

At $60\,^\circ\text{C}$, the solubility is $113\,\text{g}/100\,\text{mL}$. At $90\,^\circ\text{C}$, the solubility is $205\,\text{g}/100\,\text{cm}^3$.

Which two substances have intersecting solubility curves at $80\,^\circ\text{C}$?

Potassium chlorate and sodium chlorate.

Which substance's solubility changes the most from $0\,^\circ\text{C}$ to $100\,^\circ\text{C}$, and which changes the least?

Potassium nitrate changes the most, while sodium chlorate changes the least.

If a solution contains $140\,\text{g}$ of sodium nitrate at $65\,^\circ\text{C}$, is it saturated, unsaturated, or supersaturated?

It is saturated. At $65\,^\circ\text{C}$, only $130\,\text{g}$ of sodium nitrate can dissolve in $100\,\text{mL}\,H_2O$, so $10\,\text{g}$ will not dissolve and will crystallize out of solution.

How many additional grams of potassium chlorate must be added to a solution containing $4\,\text{g}$ at $65\,^\circ\text{C}$ to make it saturated?

$26\,\text{g}$ of solute must be added, because $30\,\text{g}$ of $KClO_3$ dissolves in $100\,\text{mL}$ of $H_2O$ at $65\,^\circ\text{C}$.

A solution contains $200\,\text{g}$ of potassium iodide dissolved in $100\,\text{cm}^3$ of water at $70\,^\circ\text{C}$. To what temperature must it cool for crystals to begin forming?

It must cool to $42\,^\circ\text{C}$, which is the temperature where the saturation limit decreases to $200\,\text{g}/100\,\text{mL}$.