chem 12 final

Electrolyte vs non-electrolyte

An electrolyte produces ions in solution and conducts electricity; a non-electrolyte does not produce ions and does not conduct electricity.

Molecular solution vs ionic solution

Molecular solutions dissolve as intact molecules; ionic solutions dissociate into ions.

Saturated solution

A solution containing the maximum amount of solute that can dissolve at a given temperature.

Solubility

The maximum amount of solute that dissolves in a given amount of solvent at a specific temperature.

Dissolving vs crystallization

• Dissolving: Forms ions in solution.
• Crystallization: Forms a solid from ions in solution.

K_{sp}

The equilibrium constant for the dissolution of a sparingly soluble ionic compound.

Predicting solubility of salts

Use solubility rules to determine if a compound is soluble, slightly soluble, or insoluble.

Low solubility

Only a small amount of the substance dissolves in solution.

Net ionic equation for Ca(NO3)2 + Li2SO4

Ca^{2+}(aq) + SO4^{2-}(aq) \rightarrow CaSO4(s)

Solubility product expression

K_{sp} equals the product of ion concentrations, each raised to its stoichiometric coefficient.

When to calculate trial K{sp} (Q{sp})

When predicting precipitate formation by comparing Q{sp} to K{sp}. If Q{sp} > K{sp}, a precipitate forms.

Amphiprotic substance example

H2O, because it can donate a proton (becoming OH^-) or accept a proton (becoming H3O^+).

Conjugate acid-base pair

Two species that differ by exactly one proton (H^+).

Strong acids vs weak acids

• Strong acids: Fully ionize (100\%) in water.
• Weak acids: Partially ionize in water.

pH and pOH definitions

• pH = -\log[H^+]
• pOH = -\log[OH^-]

K_w

K_w = [H^+][OH^-] = 1.0 \times 10^{-14} at 25 \text{ °C}.

Relationship between pH and pOH

pH + pOH = 14 (at 25 \text{ °C}).

Effect of increasing pH

pOH decreases, [H^+] decreases, [OH^-] increases, and K_{w} stays constant.

Hydrolysis

The reaction of ions with water to produce an acidic (H_3O^+) or basic (OH^-) solution.

NaNO_3 solution type

Neutral, because neither ion undergoes significant hydrolysis.

NH_4F solution type

Acidic, because NH4^+ is acidic (Ka > K_b for the pair).

LiCH_3COO solution type

Basic, because the acetate ion (CH_3COO^-) reacts with water to produce OH^-.

K_a

The acid dissociation constant; a measure of acid strength.

K_b

The base dissociation constant; a measure of base strength.

Purpose of a buffer

To resist significant changes in pH when small amounts of acid or base are added.

Metal oxide vs non-metal oxide

• Metal oxides: Generally basic in solution.
• Non-metal oxides: Generally acidic in solution.

Ways to measure reaction rate

Change in concentration, mass, gas volume, pressure, or color over time.

Factors affecting reaction rate

• Temperature
• Concentration
• Surface area
• Catalysts
• Nature of reactants

Collision theory

Reacting particles must collide with sufficient energy (activation energy) and proper orientation to result in a reaction.

Activation energy (E_a)

The minimum energy required for a collision to result in a chemical reaction.

Rate-limiting step

The slowest step in a reaction mechanism that determines the overall reaction rate.

Catalyst

A substance that increases the reaction rate by providing an alternative pathway with a lower activation energy, without being consumed.

Dynamic equilibrium

A state in a reversible reaction where the forward and reverse reaction rates are equal, and concentrations remain constant.

Conditions for equilibrium

1. Closed system
2. Constant temperature
3. Constant macroscopic properties

Randomness of phases (Entropy)

\text{Solid} \rightarrow \text{Liquid} \rightarrow \text{Gas} (Increasing randomness).

Factors affecting equilibrium

Concentration, temperature, pressure, and volume.

Le Chatelier’s Principle

If a system at equilibrium is subjected to a change, the system shifts to oppose the change and restore a new equilibrium.

Industrial applications of LCP

The Haber process (ammonia production) and the Contact process (sulfuric acid production).

Equilibrium expression (K_{eq})

The ratio of the product of the concentrations of products to the product of the concentrations of reactants, each raised to the power of their coefficients.

Meaning of K_{eq} \gg 1

Products are favored at equilibrium (equilibrium lies to the right).

Purpose of an ICE table

To organize Initial, Change, and Equilibrium concentrations to solve for unknowns in equilibrium calculations.