General Chemistry: Bonding, States of Matter, Calculations, and Solutions

Comprehensive practice flashcards covering chemical calculations, moles, stoichiometry, kinetic molecular theory, gas laws, phase changes, covalent bonding, Lewis structures, VSEPR theory, electronegativity, solutions, concentration units, colligative properties, and ionic bonding models.

What is formula mass (molecular weight), and how is it calculated?

Formula mass is the sum of the atomic masses (in $\text{amu}$) of all atoms present in the chemical formula of a substance, based on the Carbon-12 scale.

What is Avogadro's number, and what does a mole represent?

Avogadro's number ($N_A$) is $6.022 \times 10^{23}$. A mole is a counting unit equal to exactly $6.022 \times 10^{23}$ objects or particles.

How is the molar mass of a substance defined and reported?

Molar mass is the mass in grams of $1\,\text{mole}$ of a substance (atom or compound), numerically equal to its atomic or formula mass and reported in units of $\text{g/mol}$.

What conversion factor allows the conversion between moles of substance A and moles of substance B in stoichiometric calculations?

Equation coefficients from the balanced chemical reaction.

What is the difference between reactants and products in a chemical equation, and what do the state symbols $(s)$, $(l)$, $(g)$, and $(aq)$ represent?

Reactants are the starting materials that undergo chemical changes, while products are the substances produced. The state symbols represent solid $(s)$, liquid $(l)$, gas $(g)$, and aqueous solution $(aq)$.

How are theoretical yield, actual yield, and percent yield defined?

Theoretical yield is the maximum amount of product that can be derived from given amounts of reactants if no losses or inefficiencies occur. Actual yield is the amount of product actually obtained. Percent yield is calculated as: $\text{Percent yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100$.

How do solids, liquids, and gases differ in compressibility and thermal expansion?

Solids have small compressibility and very small thermal expansion (about $0.01\%\,\text{per }^\circ\text{C}$). Liquids have small compressibility (usually greater than solids) and small thermal expansion (about $0.10\%\,\text{per }^\circ\text{C}$). Gases have large compressibility and moderate thermal expansion (about $0.30\%\,\text{per }^\circ\text{C}$).

What are the five core postulates of the Kinetic Molecular Theory (KMT) of matter?

1. Matter consists of tiny particles with definite sizes that do not change. 2. Particles are in constant random motion and possess kinetic energy. 3. Particles interact through attractions and repulsions, possessing potential energy. 4. Kinetic energy increases as temperature increases. 5. Particles transfer kinetic energy through elastic collisions without net energy loss.

How do kinetic energy and potential energy act as opposing forces across the physical states of matter?

Kinetic energy acts as a disruptive force that increases with temperature, causing particles to move independently. Potential energy acts as a cohesive/attractive force that stabilizes particles and creates order, remaining independent of temperature. In solids, potential energy dominates; in liquids, both are similar in strength; in gases, kinetic energy dominates.

What device is shown in the diagram, and what pressure measurement equivalents apply at sea level?

A mercury barometer used to measure atmospheric pressure. Standard atmospheric pressure equals $1\,\text{atm} = 760\,\text{mm\,Hg} = 760\,\text{torr} = 14.7\,\text{psi}$.

What does Boyle's Law state, and what is its mathematical formula?

Boyle's Law states that the pressure and volume of a gas are inversely related at constant temperature ($T$) and molar amount ($n$): $P_1 V_1 = P_2 V_2$.

What does Charles's Law state, and what temperature scale must be used in its calculation?

Charles's Law states that the volume of a fixed amount of gas at constant pressure is directly proportional to its Kelvin temperature: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$, where $K = ^\circ\text{C} + 273$.

What is the Combined Gas Law equation?

$\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}$, which states that the product of pressure and volume of a fixed amount of gas is directly proportional to its Kelvin temperature.

What is the Ideal Gas Law equation, and what are the units and value of the gas constant $R$?

$PV = nRT$, where $P$ is pressure in $\text{atm}$, $V$ is volume in $\text{L}$, $n$ is amount in $\text{mol}$, $T$ is temperature in $\text{K}$, and $R = 0.0821\,\text{L}\cdot\text{atm}/(\text{mol}\cdot\text{K})$.

What does Dalton's Law of Partial Pressures state, and how can the partial pressure of gas A ($P_A$) be found using mole fractions?

Dalton's Law states that the total pressure exerted by a mixture of non-reacting gases is the sum of their individual partial pressures: $P_{\text{Total}} = P_1 + P_2 + P_3 + \dots$. The partial pressure of gas A is given by $P_A = \chi_A P_{\text{Total}}$, where $\chi_A = \frac{\text{moles of gas A}}{\text{total moles of gas}}$.

Which changes of state are classified as endothermic, and which are exothermic?

Endothermic changes (heat absorbed, kinetic energy increases) are melting, evaporation, and sublimation. Exothermic changes (heat released, kinetic energy decreases) are freezing, condensation, and deposition.

In the phase diagram shown, what does the 'Triple point' signify?

The unique temperature and pressure at which all three physical states of matter (solid, liquid, and gas) coexist in equilibrium.

What is vapor pressure, and what defines a volatile substance?

Vapor pressure is the pressure exerted by a vapor above a liquid when both are in physical equilibrium in a closed system. A volatile substance is one that readily evaporates at room temperature due to having a high vapor pressure.

How is the normal boiling point defined, and why does the boiling point of a liquid vary with elevation?

The normal boiling point is the temperature at which a liquid boils under an external pressure of $760\,\text{mm\,Hg}$. Boiling occurs when vapor pressure equals external atmospheric pressure; because atmospheric pressure decreases with increasing altitude, less heat is needed to match it, resulting in lower boiling points at higher elevations.

What structural conditions are required for hydrogen bonding, and what effects does it produce on liquid properties?

Hydrogen bonding requires hydrogen to be covalently bonded to a small, highly electronegative element (fluorine, oxygen, or nitrogen). It generates unusually strong dipole-dipole attractions, resulting in significantly lower vapor pressures and elevated boiling points compared to similar liquids without hydrogen bonding.

What are London dispersion forces?

Weak, temporary intermolecular forces that occur between all atoms and molecules (polar and nonpolar) resulting from momentary uneven electron distributions; they are especially significant in large atoms and molecules.

How do covalent bonds differ from ionic bonds regarding electron behavior and electrical conductivity?

Covalent bonds form through the sharing of electrons between nonmetal atoms to yield discrete molecules that do not conduct electricity. Ionic bonds form through the complete transfer of electrons from a metal to a nonmetal, generating extended crystalline arrays of ions that conduct electricity when molten or dissolved in water.

What is the difference between bonding electrons and nonbonding electrons in a molecule?

Bonding electrons are shared electron pairs located between bonded atoms that form covalent bonds. Nonbonding electrons (lone pairs or unshared electron pairs) are pairs of valence electrons on an atom that are not involved in bonding.

How do single, double, and triple bonds compare in bond order, strength, and proximity?

A single bond shares $1$ electron pair, a double bond shares $2$ pairs, and a triple bond shares $3$ pairs. The order of bond strength, proximity (atoms held closer together), and energy required to break the bond is: Triple > Double > Single.

According to the octet rule, how many covalent bonds do neutral atoms of hydrogen, carbon, nitrogen, oxygen, and the halogens normally form?

Hydrogen forms $1$ bond ($1$ vacancy), Carbon forms $4$ bonds ($4$ vacancies), Nitrogen forms $3$ bonds ($3$ vacancies), Oxygen forms $2$ bonds ($2$ vacancies), and Halogens form $1$ bond ($1$ vacancy). Halogens cannot participate in multiple covalent bonds.

What is a coordinate covalent bond?

A covalent bond in which both electrons in the shared pair come from only one of the two bonded atoms. Once formed, it is indistinguishable from a regular covalent bond, although the participating atoms deviate from their regular bonding numbers.

According to the VSEPR geometry table shown, what is the molecular geometry of a molecule with $4$ VSEPR electron groups, $2$ bonding groups, and $2$ nonbonding groups?

Angular (with an approximate bond angle of $109.5^\circ$).

What is electronegativity, and how does it trend across the periodic table?

Electronegativity is the ability of an atom in a molecule to attract shared electrons to itself. It increases from left to right across periods and from bottom to top within groups on the periodic table.

Based on the bond classification scale shown, what bond type forms when the electronegativity difference ($\Delta\text{EN}$) is between $0.4$ and $1.5$?

Polar covalent bond (characterized by unequal sharing of electrons).

What two factors determine the molecular polarity of a molecule?

1. Bond polarities (each individual bond must be evaluated; without polar bonds, a molecule cannot be polar). 2. Molecular geometry (the spatial arrangement determines whether individual bond dipoles cancel out symmetrically or result in a net dipole moment).

What rules govern the naming of binary molecular compounds?

The full name of the less electronegative nonmetal is given first with Greek numerical prefixes (omitting 'mono-' for the first element), followed by the stem of the second element with prefix and suffix '-ide'. When a prefix ends in 'a' or 'o' before oxygen, the vowel is dropped (e.g., 'monoxide', 'tetroxide'). Compounds containing hydrogen omit prefixes.

What is the definition of solubility, and how does temperature affect the solubility of solids versus gases in water?

Solubility is the maximum amount of solute that will dissolve in a given amount of solvent under specific conditions, expressed as $\text{grams of solute}/100\,\text{g H}_2\text{O}$. Increasing temperature generally increases the solubility of solid solutes, but always decreases the solubility of gas solutes.

What does Henry's Law state regarding gas solubility in liquids?

Henry's Law states that the amount of gas that will dissolve in a liquid at a given temperature is directly proportional to the partial pressure of the gas above the liquid.

What distinguishes saturated, unsaturated, and supersaturated solutions?

A saturated solution contains the maximum amount of dissolved solute possible at given conditions. An unsaturated solution contains less than the maximum amount. A supersaturated solution is an unstable state containing more dissolved solute than a saturated solution under those conditions, typically formed by cooling a heated saturated solution.

What three factors increase the rate of solution formation?

1. State of subdivision of the solute (smaller pieces provide greater surface area). 2. Degree of agitation (stirring moves particles and accelerates contact). 3. Temperature of the solution components (higher kinetic energy causes particles to move and collide more rapidly).

What are the formulas for mass percent, volume percent, and mass-volume percent concentration?

$\text{Percent by mass} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100$, $\text{Percent by volume} = \frac{\text{volume of solute}}{\text{volume of solution}} \times 100$, and $\text{Mass-volume percent} = \frac{\text{mass of solute (g)}}{\text{volume of solution (mL)}} \times 100$.

How is molarity defined, and what is the mathematical formula for dilution calculations?

Molarity ($M$) is the number of moles of solute divided by liters of solution ($M = \frac{\text{moles of solute}}{\text{liters of solution}}$). The dilution formula is: $C_s \times V_s = C_d \times V_d$, where $C$ is concentration and $V$ is volume for the stock ($s$) and diluted ($d$) solutions.

What phenomenon is shown in the right beaker, and how does it differentiate a colloidal dispersion from a true solution?

The Tyndall effect. Light passing through a true solution is not visible because dissolved particles are tiny atoms, ions, or molecules, whereas a colloidal dispersion scatters light because the dispersed particles are larger groups of molecules, making the light beam path observable.

What is a colligative property, and what are the four primary colligative properties of solutions?

A colligative property is a physical property that depends only on the number of solute particles present in a given solvent, not on their chemical identity. The four examples are: 1. Vapor-pressure lowering, 2. Boiling-point elevation, 3. Freezing-point depression, and 4. Osmotic pressure.

What is osmosis, and how is osmolarity calculated?

Osmosis is the passage of solvent through a semipermeable membrane from a dilute solution (or pure solvent) into a more concentrated solution. Osmolarity is calculated as the product of a solution's molarity ($M$) and the number of particles produced per formula unit ($i$): $\text{Osmolarity} = i \times M$.

What cellular processes are depicted in images (a) and (b) when red blood cells are placed in hypotonic and hypertonic solutions, respectively?

Image (a) shows hemolysis (cell swelling and bursting due to net water flow into the cell in a hypotonic solution). Image (b) shows crenation (cell shrinkage due to net water flow out of the cell in a hypertonic solution).

What are valence electrons, and how can they be determined for representative elements?

Valence electrons are the electrons in the outermost shell (highest principal quantum number $n$, involving $s$ and $p$ subshells) of an atom. For representative elements, the number of valence electrons corresponds to the Roman numeral periodic-table group number, up to a maximum of eight.

What is the octet rule?

The principle that in forming compounds, atoms of elements lose, gain, or share electrons to attain a stable, noble-gas electron configuration consisting of completely filled $s$ and $p$ subshells ($ns^2 np^6$), containing eight valence electrons.

What ionic charges are typically acquired by representative elements in Groups IA, IIA, IIIA, VA, VIA, and VIIA?

Metals lose electrons: Group IA forms $1+$, Group IIA forms $2+$, and Group IIIA forms $3+$. Nonmetals gain electrons: Group VA forms $3-$, Group VIA forms $2-$, and Group VIIA forms $1-$.

What are isoelectronic species?

Atoms and ions, or pairs of ions, that possess the exact same number and configuration of electrons (for example, $\text{N}^{3-}$, $\text{O}^{2-}$, $\text{F}^-$, $\text{Na}^+$, $\text{Mg}^{2+}$, and $\text{Al}^{3+}$ all have the $1s^2 2s^2 2p^6$ configuration).

What concept is highlighted in the diagram as the smallest whole-number repeating ratio of ions in an ionic compound?

A formula unit.

Which transition and post-transition metals shown in the chart possess fixed ionic charges and do NOT use Roman numerals when named?

Silver ($\text{Ag}^+$), Zinc ($\text{Zn}^{2+}$), Cadmium ($\text{Cd}^{2+}$), Aluminum ($\text{Al}^{3+}$), and Gallium ($\text{Ga}^{3+}$).

What are the names, chemical formulas, and charges of common polyatomic ions containing nitrogen, sulfur, and phosphorus?

Nitrate is $\text{NO}_3^-$, ammonium is $\text{NH}_4^+$, sulfate is $\text{SO}_4^{2-}$, hydrogen sulfate (bisulfate) is $\text{HSO}_4^-$, phosphate is $\text{PO}_4^{3-}$, hydrogen phosphate is $\text{HPO}_4^{2-}$, and dihydrogen phosphate is $\text{H}_2\text{PO}_4^-$.