Liquids, Solids, and Intermolecular Forces Practice Flashcards

Comprehensive practice questions covering vaporization, dynamic equilibrium, phase diagrams, heating curves, and crystalline unit cell structures.

How does surface area affect the rate of evaporation?

The larger the surface area, the faster the rate of evaporation because more high-energy molecules are at the surface where they can escape.

What is the difference between volatile and nonvolatile liquids?

Volatile liquids evaporate easily (e.g., gasoline), while nonvolatile liquids do not evaporate easily (e.g., motor oil).

According to the energetics of state changes, are vaporization and condensation endothermic or exothermic?

Vaporization is an endothermic process (requires energy input), while condensation is an exothermic process (releases energy).

What is the definition of the heat of vaporization ($\Delta H_{vap}$)?

The amount of heat energy required to vaporize one mole of a liquid.

How is the change in enthalpy for condensation ($\Delta H_{condensation}$) related to the heat of vaporization?

$$\Delta H_{condensation} = -\Delta H_{vaporization}$$

Define dynamic equilibrium in the context of a closed container.

The state where the rates of vaporization and condensation are equal, resulting in no net gain or loss of liquid or vapor.

What is vapor pressure?

The pressure exerted by a vapor when it is in dynamic equilibrium with its liquid.

How do intermolecular forces affect vapor pressure?

The weaker the attractive forces among molecules, the higher the vapor pressure.

What is the boiling point of a liquid?

The temperature at which the vapor pressure of the liquid equals the external pressure.

What is the normal boiling point?

The temperature at which the vapor pressure of a liquid is exactly $1\,atm$.

In a graph representing the Clausius–Clapeyron Equation, what are the axes and what does the slope represent?

The graph plots $\ln(P_{vap})$ vs. $1/T$. The slope of the resulting straight line is $-\frac{\Delta H_{vap}}{R}$, where $R = 8.314\,J/mol \cdot K$.

Write the two-point form of the Clausius–Clapeyron Equation.

$$\ln\left(\frac{P_2}{P_1}\right) = -\frac{\Delta H_{vap}}{R} \left(\frac{1}{T_2} - \frac{1}{T_1}\right)$$

What is a supercritical fluid?

A state of matter formed when a liquid is heated to its critical temperature in a sealed container, where the meniscus disappears and the substance has properties of both gas and liquid.

What occurs at the triple point in a phase diagram?

The specific temperature and pressure condition where all three states (solid, liquid, and gas) coexist in equilibrium.

Define sublimation and deposition.

Sublimation is the transition from solid directly to gas; deposition is the transition from gas directly to solid.

What is the heat of fusion ($\Delta H_{fus}$)?

The amount of heat energy required to melt one mole of a solid.

Why does ice float on liquid water?

Water expands when it freezes at a pressure of $1\,atm$, making ice about $9\%$ less dense than liquid water.

What is the specific heat ($C_s$) of liquid water?

$$4.18\,J/g^{\circ}C$$

State Bragg's Law for X-ray crystallography.

$n\lambda = 2d\sin(\theta)$, where $\lambda$ is wavelength, $d$ is crystal layer spacing, and $\theta$ is the incident angle.

What is a unit cell?

The smallest unit that shows the pattern of arrangement for all particles in a crystal lattice.

How many atoms are in a Simple Cubic, Body-Centered Cubic (BCC), and Face-Centered Cubic (FCC) unit cell?

Simple Cubic: $1$ atom; BCC: $2$ atoms; FCC: $4$ atoms.

What is the coordination number and packing efficiency of a Face-Centered Cubic (FCC) unit cell?

Coordination number is $12$ and packing efficiency is $74\%$..

What is the edge length ($l$) of a Body-Centered Cubic (BCC) unit cell in terms of the atomic radius ($r$)?

$$l = \frac{4r}{\sqrt{3}}$$