CHEM 1410 Exam 3 Review: Thermochemistry, Quantum Mechanics, and Periodic Trends

Comprehensive question-and-answer flashcards covering key concepts for Exam 3 in CHEM 1410, including thermochemical formulas, quantum mechanics and orbital filling rules, periodic trends, and the metal activity series.

What equation is used to calculate the quantity of heat ($q$) absorbed or released by a substance from its mass, specific heat, and temperature change?

$q = m \times C_s \times \Delta T$, where $m$ is mass, $C_s$ is the specific heat capacity, and $\Delta T$ is the temperature change.

In constant-pressure calorimetry with negligible heat absorbed by the calorimeter ($q_{\text{cal}} = 0$), how are $q_{\text{reaction}}$ and $\Delta H_{\text{reaction}}$ determined?

$q_{\text{reaction}} = -q_{\text{solution}} = -(\text{mass}_{\text{solution}} \times C_{s, \text{solution}} \times \Delta T)$. At constant pressure, $\Delta H_{\text{reaction}} = q_{\text{reaction}}$. To express $\Delta H_{\text{reaction}}$ per mole, divide by the number of moles.

What is the formula for calculating the standard enthalpy change of a reaction ($\Delta H_{\text{rxn}}^\circ$) using standard enthalpies of formation ($\Delta H_f^\circ$)?

$$\Delta H_{\text{rxn}}^\circ = \sum n\Delta H_f^\circ(\text{products}) - \sum m\Delta H_f^\circ(\text{reactants})$$

What equations relate the speed of light, wavelength, frequency, and photon energy, and what are the constants $h$ and $c$?

The equations are $\lambda \times \nu = c$ and $E = h \times \nu = \frac{h \times c}{\lambda}$, where Planck's constant is $h = 6.626 \times 10^{-34}\,\text{J}\cdot\text{s}$ and the speed of light is $c = 3.00 \times 10^8\,\text{m/s}$.

What are the allowed values for the angular momentum quantum number ($l$) for a given value of $n$, and what subshell letter corresponds to each value of $l$?

For a given $n$, $l = 0, 1, 2, 3, \dots, n - 1$. The subshell designations are: $l = 0$ is an $s$ orbital, $l = 1$ is a $p$ orbital, $l = 2$ is a $d$ orbital, and $l = 3$ is an $f$ orbital.

What does the magnetic quantum number ($m_l$) describe, and what are its possible values for a given value of $l$?

$m_l$ is related to the orientation of an orbital in space relative to other orbitals with the same $l$. Its values range from $-l$ to $+l$ ($m_l = -l, \dots, 0, \dots, +l$). For example, if $l = 1$, $m_l = -1, 0, 1$, and if $l = 2$, $m_l = -2, -1, 0, 1, 2$.

What is the maximum electron capacity of a single orbital, each subshell ($s$, $p$, $d$), and a principal shell $n$?

Each individual orbital holds a maximum of $2$ electrons. A single $s$ orbital holds $2$ electrons, a $p$ subshell holds $6$ electrons ($3 \times 2$), a $d$ subshell holds $10$ electrons ($5 \times 2$), and the maximum number of electrons in a given shell is $2n^2$.

According to the diagonal rule diagram shown, what is the order of orbital filling from lowest energy up to $6s$?

$$1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s\dots$$

What is Hund's rule regarding the arrangement of electrons in orbitals of equal energy?

The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins; whenever orbitals of equal energy are available, electrons occupy these orbitals singly before pairing begins.

What is the distinction between a paramagnetic substance and a diamagnetic substance?

A paramagnetic substance contains one or more unpaired electrons, whereas a diamagnetic substance has all of its electrons paired.

What is the periodic trend for atomic radius across a period and down a group?

Atomic radius decreases across a period (left to right) and increases down a group (top to bottom).

What is effective nuclear charge ($Z_{\text{eff}}$), and how does it trend across the periodic table?

Effective nuclear charge is the positive charge felt by an electron. It increases across a period (left to right) and decreases down a group (top to bottom).

How is first ionization energy defined, and what is its periodic trend?

First ionization energy is the energy needed to remove an electron from a gaseous atom. It increases across a period (left to right) and decreases down a group (top to bottom).

What is electronegativity, and how does it trend across a period and down a group?

Electronegativity is the ability of an atom to attract electrons to itself in a chemical bond. It increases across a period (left to right) and decreases down a group (top to bottom).

What is the periodic trend for metallic character, and what property is it consistent with?

Metallic character decreases across a period (left to right) and increases down a group (top to bottom). It is consistent with the trend for the basicity of oxides.

How do the metals at the top of the Activity Series ($\text{Li}$, $\text{K}$, $\text{Ba}$, $\text{Ca}$, and $\text{Na}$) react with water and acids?

They react with cold water to produce $\text{H}_2$ and also react with acids to produce $\text{H}_2$.

Which metals in the Activity Series react with steam and acids to produce $\text{H}_2$, but do not react with cold water?

$\text{Mg}$, $\text{Al}$, $\text{Zn}$, $\text{Cr}$, $\text{Fe}$, and $\text{Cd}$.

Which metals react with acids to produce $\text{H}_2$ but do not react with water, and which metals do not react with water or acids to produce $\text{H}_2$?

$\text{Co}$, $\text{Ni}$, $\text{Sn}$, and $\text{Pb}$ react with acids to produce $\text{H}_2$ but do not react with water. $\text{Cu}$, $\text{Ag}$, $\text{Hg}$, $\text{Pt}$, and $\text{Au}$ do not react with water or acids to produce $\text{H}_2$.

How do reactivity, ease of oxidation, and the tendency to lose electrons change from the top to the bottom of the Activity Series for metals?

Metals at the top are the most reactive, most easily oxidized, and have the strongest tendency to lose electrons. As you move down the series, metals become least reactive, most difficult to oxidize, and have the least tendency to lose electrons.