CHEM204 - Physical Chemistry: Thermodynamics, Kinetics & Quantum Basics Flashcards

Question 1

Zeroth Law of Thermodynamics

Accepted Answer

States that if two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This law provides the fundamental basis for the definition of temperature.

Question 2

First Law of Thermodynamics

Accepted Answer

The law of conservation of energy: $\Delta U = q + w$, where $\Delta U$ is the change in internal energy, $q$ is heat added to the system, and $w$ is work done on the system.

Question 3

Second Law of Thermodynamics

Accepted Answer

States that the total entropy of an isolated system always increases over time for a spontaneous process: $\Delta S_{\	ext{univ}} = \Delta S_{\	ext{sys}} + \Delta S_{\	ext{surr}} \ge 0$.

Question 4

Third Law of Thermodynamics

Accepted Answer

States that the entropy of a perfect, pure crystalline substance approaches zero as the absolute temperature approaches zero Kelvin ($T \	o 0\	ext{ K} \implies S \	o 0$).

Question 5

State Function vs. Path Function

Accepted Answer

A **state function** depends only on the current state of the system (e.g., $U$, $H$, $S$, $G$, $P$, $V$, $T$). A **path function** depends on the specific mechanism or route taken between states (e.g., heat $q$ and work $w$).

Question 6

Gibbs Free Energy Equation

Accepted Answer

Defined as $\Delta G = \Delta H - T\Delta S$. At constant temperature and pressure, a reaction is spontaneous if $\Delta G < 0$, at equilibrium if $\Delta G = 0$, and non-spontaneous if $\Delta G > 0$.

Question 7

Standard Gibbs Free Energy & Equilibrium Constant

Accepted Answer

Relates the standard Gibbs energy change to the equilibrium constant $K$: $\Delta G^\circ = -RT \ln K$. If $K > 1$, $\Delta G^\circ < 0$ and products are favored at equilibrium.

Question 8

Nernst Equation

Accepted Answer

Calculates cell potential under non-standard conditions: $E = E^\circ - \frac{RT}{nF}\ln Q$, or at $298.15\	ext{ K}$, $E = E^\circ - \frac{0.0592}{n}\log_{10} Q$, where $n$ is electron moles transferred and $Q$ is the reaction quotient.

Question 9

Reaction Quotient ($Q$) vs. Equilibrium Constant ($K$)

Accepted Answer

$Q$ measures product-to-reactant activity ratios at any point in time; $K$ measures it at equilibrium. If $Q < K$, the forward reaction is favored ($E > E^\circ$); if $Q > K$, the reverse reaction is favored.

Question 10

Integrated Rate Law: Zero-Order

Accepted Answer

Equation: $[A]_t = -kt + [A]_0$
- **Linear Plot:** $[A]_t$ vs. $t$ (slope $= -k$)
- **Half-life:** $t_{1/2} = \frac{[A]_0}{2k}$
- **Units of $k$:** $\	ext{M} \cdot \	ext{s}^{-1}$

Question 11

Integrated Rate Law: First-Order

Accepted Answer

Equation: $\ln[A]_t = -kt + \ln[A]_0$
- **Linear Plot:** $\ln[A]_t$ vs. $t$ (slope $= -k$)
- **Half-life:** $t_{1/2} = \frac{\ln 2}{k} \approx \frac{0.693}{k}$ (independent of initial concentration)
- **Units of $k$:** $\	ext{s}^{-1}$

Question 12

Integrated Rate Law: Second-Order

Accepted Answer

Equation: \frac{1}{[A]_t} = kt + \frac{1}{[A]_0}
- **Linear Plot:** \frac{1}{[A]_t} vs. $t$ (slope $= +k$)
- **Half-life:** $t_{1/2} = \frac{1}{k[A]_0}$
- **Units of $k$:** $\	ext{M}^{-1} \cdot \	ext{s}^{-1}$

Question 13

Arrhenius Equation

Accepted Answer

Relates rate constant $k$ to absolute temperature $T$ and activation energy $E_a$: $k = A e^{-\frac{E_a}{RT}}$. Linearized form: $\ln k = -\frac{E_a}{R}\left(\frac{1}{T}\ight) + \ln A$.

Question 14

Catalyst Effect on Reaction Kinetics and Thermodynamics

Accepted Answer

A catalyst increases reaction rate by offering an alternative pathway with lower activation energy ($E_a$). It speeds up both forward and reverse rates equally without changing $\Delta G$, $\Delta H$, or equilibrium constant $K$.

Question 15

De Broglie Wavelength

Accepted Answer

Describes the wave nature of matter: $\lambda = \frac{h}{p} = \frac{h}{mv}$, where $h$ is Planck's constant, $p$ is momentum, $m$ is mass, and $v$ is velocity.

Question 16

Heisenberg Uncertainty Principle

Accepted Answer

States that position and momentum cannot be simultaneously measured with arbitrary precision: $\Delta x \cdot \Delta p_x \ge \frac{\hbar}{2}$, where $\hbar = \frac{h}{2\pi}$.

Question 17

Time-Independent Schrödinger Wave Equation

Accepted Answer

Fundamental quantum state equation: $\hat{H}\psi = E\psi$, where $\hat{H}$ is the Hamiltonian operator ($-\frac{\hbar^2}{2m}\
abla^2 + V$), $\psi$ is the wave function, and $E$ is total energy.

Question 18

Physical Meaning of Wave Function (Born Interpretation)

Accepted Answer

The wave function $\psi$ itself is not directly measurable, but $|\psi|^2$ (or $\psi^*\psi$) represents the **probability density** of finding a particle in a given region of space.

Question 19

Particle in a 1D Box (Infinite Potential Well)

Accepted Answer

A foundational quantum model where $V=0$ inside $0 \le x \le L$ and $V=\infty$ elsewhere. Quantized energy levels are given by $E_n = \frac{n^2 h^2}{8mL^2}$ for quantum numbers $n = 1, 2, 3, \dots$

Question 20

Zero-Point Energy

Accepted Answer

The lowest possible quantum energy state a system can possess ($n=1$ in a particle-in-a-box model: $E_1 = \frac{h^2}{8mL^2}$). Quantum mechanics dictates energy can never be strictly zero due to the Uncertainty Principle.

CHEM204 - Physical Chemistry: Thermodynamics, Kinetics & Quantum Basics

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