*** EXAM DATE: NOVEMBER 24 ***
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1. THE GASEOUS STATE
Gas Laws and Stoichiometry
Gases are characterized by four variables: **Pressure ($P$), Volume ($V$), Temperature ($T$),** and **Amount ($n$, moles)**.
| Concept | Key Principle / Equation | Notes & Variables |
|---|---|---|
| **Ideal Gas Law** | \(PV = nRT\) | **T** must be in **Kelvin (K)**. $R$ is the gas constant ($0.0821 \text{ L}\cdot\text{atm}/\text{mol}\cdot\text{K}$). |
| **Combined Gas Law** | \(\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}\) | Used when amount of gas ($n$) is constant. |
| **Dalton's Law of Partial Pressures** | \(P_{\text{total}} = P_1 + P_2 + \dots\) | Total pressure is the sum of **partial pressures**. |
Stoichiometry with Gases
The Ideal Gas Law converts gas properties ($P, V, T$) into the **amount in moles** ($n$) for reaction calculations.
2. LIQUID AND SOLID STATES, PHASE CHANGES, & CHEMISTRY OF WATER
Intermolecular Forces (IMFs)
- IMFs are the attractive forces **between** molecules. They are **broken** during melting or vaporization.
- **Intramolecular Bonds** are the forces **within** molecules and are **not** typically broken during phase changes.
The Chemistry of Water
Water's unique properties stem from its strong **Hydrogen Bonding** capabilities:
- **Density Anomaly:** **Ice is less dense than liquid water** because H-bonds lock the molecules into an open, hexagonal crystal lattice structure.
3. SOLUTIONS, ELECTROLYTES, AND COLLIGATIVE PROPERTIES
Electrolytes and $i$ Factor
- **Strong Electrolytes:** Substances that **dissociate completely** (e.g., $NaCl$). Van't Hoff factor, **$i > 1$**.
- **Non-electrolytes:** Substances that dissolve but **do not ionize** (e.g., sugar, \(C_{12}H_{22}O_{11}\)). **$i = 1$**.
Colligative Properties
These properties depend solely on the **concentration of solute particles**.
| Property | Equation | Concentration Unit |
|---|---|---|
| **Freezing/Boiling Point Change** | \(\Delta T_{f/b} = i K_{f/b} m\) | **Molality ($m$):** \(\frac{\text{moles solute}}{\text{kg solvent}}\) |
| **Osmotic Pressure** ($\Pi$) | \(\Pi = i c R T\) | **Molarity ($c$):** \(\frac{\text{moles solute}}{\text{L solution}}\) |
4. & 5. CHEMICAL EQUILIBRIUM
The Equilibrium Constant ($K$)
For a general reaction: $aA + bB \rightleftharpoons cC + dD$
The equilibrium constant expression is:
\begin{equation*} K_c = \frac{[C]^c [D]^d}{[A]^a [B]^b} \end{equation*}- $K$ only depends on **Temperature ($T$)**.
- Pure solids and pure liquids are **omitted** from the $K$ expression.
Le Châtelier's Principle
A system at equilibrium will shift to **counteract** any applied stress.
| Stress Applied | Shift Direction | Effect on \(K\) |
|---|---|---|
| **Increase $T$** (Exothermic, \(\Delta H < 0\)) | Shift **Left** (consumes heat). | **Decreases $K$** |
| **Pressure/Volume Change** | Shift toward side with **fewer/more moles of gas**. | **No Change** |