Download Inorganic ACS Study Guide questions with verified solutions and more Exams Nursing in PDF only on Docsity!
Inorganic ACS Study Guide
questions with verified
solutions
Define ionization energy. - correct answer(s) ✔✔ The energy required to remove the least tightly bound electron from a neutral atom in the gas phase Describe the periodic trend in ionization energy. - correct answer(s) ✔✔ Lowest I.E. starts at the bottom left corner of the periodic table and increases going up and to the right What is the real reason that a half-filled subshell is so stable? - correct answer(s) ✔✔ It serves to maximize the stabilizing interactions, while minimizing the destabilizing interactions among electrons. What is the exchange interaction? Is it stabilizing or destabilizing? - correct answer(s) ✔✔ The exchange interaction, πe, a stabilizing interaction, and it is a result of electrons pairing in degenerate orbitals with parallel spin What is the pairing energy? Is it stabilizing or destabilizing? - correct answer(s) ✔✔ Pairing energy is a destabilizing interaction, the coulomb interaction, πC, and it is the energy of electron-electron repulsion in a filled orbital. What is harder to ionize, a high energy electron or a low energy electron? - correct answer(s) ✔✔ A high energy electron is easier to ionize. It already contains more energy, so the input to remove it from the atom is less.
If a 3d series metal is ionized, what orbital loses the electron? What happens to the valence configuration? - correct answer(s) ✔✔ If a d series metal has the configuration 4s²3d^n, the first electron to be ionized will come from the 4s orbital. The remaining s orbital will then enter a d orbital, giving the configuration of the +1 cation 4s03dn+1. What is the Lanthanide Contraction? - correct answer(s) ✔✔ It is the reduction in atomic radius following the lanthanide series, contrary to the overall trend observed for the periodic table. The lanthanides are elements 57 through 71, and are the first appearance of filled f orbitals. F orbitals are poor at shielding, so any electrons added into the subshell following the f orbital experience a higher Zeff, shrinking their radius over what is to be expected from overall trends. Describe Slater's Rule. - correct answer(s) ✔✔ Slater's Rules tell us what the effective nuclear charge will be. Formally, it is written as Zeff= Z - σ. Z is the atomic number, and σ=Σsi Si is the number of electrons in a given subshell multiplied by a weighting coefficient. The weighting coefficients are:
- A. For s and p valence electrons, (n-2) groups or lower contribute 1.00 to si (weighting coefficient of 100%). 1.00xne B. (n-1) groups contribute 0.85 to si. 0.85xne C. N(s,p) groups (the valence groups) contribute 0.35 to si. 0.35xne
- For d and f valence electrons: A. electrons in the valence shell contribute 0.35 to si. 0.35xne B. electrons in any lower group contribute 1.00 to si. 1.00xne What is shielding? - correct answer(s) ✔✔ Shielding is the reduction in charge attraction between the nucleus and electrons, due to electrons between the nucleus and the electron in
energy levels. R is the Rydberg constant, which = 1.09737x10^5 cm-1, c is the speed of light in cm, 2.998x10^10 ms-1 , and h is Plank's constant, 6.626x10^-34 Js. What is another way of expressing the energy? Joules, and... - correct answer(s) ✔✔ Wavenumbers, which are the inverse of wavelength, expressed as inverse centimeters. Define and describe the quantum numbers n, l, ml, ms. - correct answer(s) ✔✔ N: The principle quantum number. It defines the energy and size of the orbital. L: Orbital angular momentum quantum number: it defines the magnitude of the orbital angular momentum, as well as the angular shape of the orbital. L can have values of 0 to n-1. Ml: Magnetic Quantum number: Describes the orientation of the angular momentum. Ml can have values of 0 to +/- l. Ms: Spin magnetic quantum number: Defines the intrinsic angular momentum of an electron. Ms can have values of either +1/2 or -1/2. It can be seen from these definitions that every electron in an atom or molecule will have a different set of quantum numbers. What is the radial wavefunction? - correct answer(s) ✔✔ The radial wavefunction (R(r)), along with the angular wavefunction (spherical harmonic), gives us the orbitals. With a wavefunction, it is possible to completely characterize a particle. The wavefunction does not go to zero at the nucleus, they go to zero at infinity. When graphed, these produce the characteristic shapes of the orbitals we are used to seeing. What is the radial distribution function? - correct answer(s) ✔✔ It is a plot of R²(r)r² vs the radius. It tells us the probability of finding an electron at a certain distance from the nucleus. Every orbital has a different radial distribution function, and a node on the graph is a region of zero probability. d. What is the Bohr radius? - correct answer(s) ✔✔ The Bohr radius is the most probably distance to find the electron in a one proton, one electron system. It is: a0= (ε0ђ²)/(π(me)e²)= 52.9 pico-meters.
What orbitals correspond to l=0 through l=4? - correct answer(s) ✔✔ =0=s, l=1=p, l=2=d, l=3=f, l=4=g. What is the building up principle/Hund's Rules? - correct answer(s) ✔✔ When degenerate orbitals are available for occupation, electrons occupy separate orbitals with parallel spin. What is the Pauli exclusion principle? - correct answer(s) ✔✔ No more than two electrons can occupy a single orbital, and to do so, their spins must be paired. Describe Valence Shell Electron Pair Repulsion Theory. - correct answer(s) ✔✔ The purpose of VSEPR theory is to predict molecular geometries. The basic assumption to the theory is that regions of enhanced electron density take positions as far apart as possible, in order to minimize repulsive forces. The relative repulsive strengths of electron dense regions are: lone pairs > multiple bonds > single bonds. Be able to predict molecular shapes based on VSEPR theory - correct answer(s) ✔✔ IDK how to import pictures into quizlet so you're on your own. Describe valence bond theory. - correct answer(s) ✔✔ Valence bond theory explains chemical bonding by considering the overlap of atomic orbitals. The wave patterns of atomic orbitals interfere constructively to form a bond. A σ bond is formed when orbital overlap of atomic orbitals with cylindrical symmetry. A π bond forms when atomic orbitals overlap side by side, after the formation of a σ bond. Hybridization is used to explain bonding where the number of equivalent bonds exceeds the number of valence orbitals. (Also go look at the picture in the study guide) What is the effect of a lone pair on geometry? - correct answer(s) ✔✔ A lone pair pushes strongly against all other substituents. It is the strongest steric force governing the shape of a molecule.
interaction, the frontier orbitals are the point of interaction and basis of understanding for molecular interactions. How is paramagnetism identified through a MO diagram? - correct answer(s) ✔✔ If there are two unpaired electrons, the species is paramagnetic. Define Metallic bonding: - correct answer(s) ✔✔ the bonding and ordering of metals into pure solids, or solid solutions, viewed as enormous molecules with continually overlapping atomic orbitals. Define ionic bonding. - correct answer(s) ✔✔ ions of different elements held together in rigid, symmetrical arrays as a result of attraction between their opposite charges Define Lattice - correct answer(s) ✔✔ A 3D infinite array of (lattice) points which define the repeating structure of a crystal. Define Unit Cell - correct answer(s) ✔✔ an imaginary, parallel sided region from which the entire crystal can be built, such that it fits perfectly together, giving rise to a crystal system. There are 7 types of crystal systems: cubic, tetragonal, orthorhombic (3 different length dimensions, identical angles), monoclinic (3 different dimensions, defining angle between two sides), triclinic (3 different dimensions, 3 different angles), rhombohedral (all 3 sides the same length, all angles are equal and non-90), and hexagonal. Define primitive cell - correct answer(s) ✔✔ Contains only one lattice point. Define Body Centered - correct answer(s) ✔✔ two lattice points per unit cell define face centered - correct answer(s) ✔✔ Four lattice points per unit cell
Define centered cubic - correct answer(s) ✔✔ 3D version of body centered Define Close packed structure - correct answer(s) ✔✔ structure type with the least unfilled space Define coordination number. - correct answer(s) ✔✔ The number of nearest neighbors. It is the number of other spheres that a single sphere is touching in its unit cell Define cubic close-close packed - correct answer(s) ✔✔ ABCABC repeating layers (ABAB results in hexagonally close packed) Define face-centered cubic - correct answer(s) ✔✔ the same thing as cubic close-packed. Define hole. - correct answer(s) ✔✔ unoccupied space between spheres. Holes can be octahedral, where they lie between two triangles and form a hexagon. They can also be tetrahedral, where it is formed by a planar triangle of touching spheres. Define polymorphism. - correct answer(s) ✔✔ The ability of a metal to adopt different crystal structures based on the temperature and pressure. Define Alloy - correct answer(s) ✔✔ A blend of different metals. More formally called a solid solution. Define Substitutional solid solution - correct answer(s) ✔✔ When solute metal atoms take up the positions of solvent metal atoms in the crystal structure. Define interstitial solid solution - correct answer(s) ✔✔ When the solute metal atoms take up positions in the holes (interstices) of the solvent crystal structure.
Define band - correct answer(s) ✔✔ A near continuous array of energy levels, due to the large number of symmetrically oriented atomic orbitals in a solid with very similar energy levels. Define band gap - correct answer(s) ✔✔ A separation of bands, due to there being no energy value for the molecular orbital. define s/p band - correct answer(s) ✔✔ The bands built from s and p orbitals. define fermi level. - correct answer(s) ✔✔ The highest occupied energy level in a solid at T=0. What are the parameters for a substitutional solid solution? - correct answer(s) ✔✔ 1) The atomic radii of the elements are with about 15% of each other.
- The crystal structures of the two pure metals are the same. This indicates that the directional forces between the two atom types are compatible with each other.
- The electropositive characteristics of both compounds are similar. Otherwise, electron transfer would be likely. What are the parameters for an interstitial solid solution? - correct answer(s) ✔✔ Interstitial solid solutions usually form between metals and small atoms (group 2). In order for the compound to form, the small atom must not transfer electrons, or an ionic species would result. For the small atom to fit in the hole, its radius must be close to 0.414x(radius metal). Interstitial compounds can have a recognizable molecular formula, or they can form non- stoichiometric compounds. Describe how to write a Born-Haber cycle, and give an example. (formatting looks like shit be warned) - correct answer(s) ✔✔ Starting from the solid of interest, of form MX(s):
- Standard molar enthalpy of decomposition, ΔdH0 (the negative of the standard molar enthalpy of formation, ΔfH0). MX(s) -> M(s) + X(s, l, g) (elements are now in their reference states)
- Standard molar enthalpy of atomization for a solid, ΔatomH0 is the same thing as sublimation M(s) -> M(g), ΔatomH
- Standard molar enthalpy of atomization for an element is the same thing as the standard enthalpy of dissociation, ΔdisH X2(g) -> 2X(g), ΔdisH
- The standard molar enthalpy of formation of ions from neutral atoms is the enthalpy of ionization (cations) and election gain enthalpy (anions). M(g) -> M+(g) + e-, ΔionH X(g) + e- -> X-(g), ΔegH For a complete cycle, the total change in enthalpy will be zero. ΔdH0, ΔatomH0, ΔdisH0, and ΔionH0 are all positive, and ΔegH0 is negative. The value required to make this equal zero is the value for the lattice enthalpy, ΔHL0, and it will be negative. What is the most stabilizing influence on a solid? Set up a proportion to show how it changes along with the values, and relate this to different types of systems. - correct answer(s) ✔✔ Lattice enthalpy is the most stabilizing influence on a solid. ΔHL⁰ ≈ q¹q²/d, if the charge is high and distance small, lattice enthalpy is very strongly stabilizing. If the charge is small and the distance is great, the solid is not especially stable. ΔHL⁰ values are at their highest when the solid is tightly packed, and the ions are charge dense. f. Discuss the importance of the Born-Mayer equation. (I did not format the equation because no) - correct answer(s) ✔✔ The Born-Mayer equation allows us to estimate the lattice enthalpy from charge and separation, at T=0. ΔHL0= (((6.022×〖 10 〗^23 )×√((q"1" q"2" )^2 )×e^2)/4πϵd)×(1-(d^/d))×A Where d is the distance between neighboring cations and anions, d is a constant, A is the Madelung constant, and ε is the permittivity.
neighbors. Because of the near continuum of MO's, the energy separation between neighboring orbitals approaches zero, creating a near continuous energy spectrum. The s-band forms between s orbitals, the p-band between p orbitals, etc... There may be a gap (band gap) between orbital bands, or they may overlap. Conductors have partially filled bands at low energy levels, so electrons are promoted easily. Vigorous vibrations, such as those due to thermal energy, disrupt the band structure, and decrease conductivity. Insulators have filled bands with a large energy differential separating them. The filled band is called the valence band, and the next higher band is called the conduction band.(Refer to picture in study guide Define Instrinsic semiconductor - correct answer(s) ✔✔ like insulators, they have a filled s- band and empty p-band, but the energy gap is very small. This makes it so that electrons can be promoted by thermal energy. The promotion of electrons results in positive holes in the valence band, amounting to a charge separation, which allows current to flow. The population of the conduction band shows an Arrhenius-like dependence on temperature. Define Extrinsic Semiconductors. Define N- and P-type. - correct answer(s) ✔✔ A material gains the ability to be a semiconductor because of intentionally added impurities (dopants), which increase the number of electron carriers. a. N-type: the N meaning negative, the dopant supplies additional electrons to the solid structure. These electrons lie above the valence band in energy, and close to the conduction band, so the gap is much easier to jump, thanks to the donor band. b. P-type: The P means positive, the dopant material has less valence electrons than the parent material. The holes it creates lie just above the valence band in energy, so electrons can jump to the acceptor band to allow current to flow. What conditions are needed for electrons to flow through a solid? - correct answer(s) ✔✔ A small energy difference and unfilled orbitals
Define a Lewis acid/base. - correct answer(s) ✔✔ A Lewis acid is an electron pair acceptor, and a Lewis base is an electron pair donor. Define a Bronsted-Lowry acid/base. - correct answer(s) ✔✔ A Bronsted acid is a proton donor, and a Bronsted base is a proton acceptor. Obviously, this theory focuses on proton transfer as the source of acidity. Define hard/soft acid/base theory (HSAB). - correct answer(s) ✔✔ Hard acids bond in order of: I- < Br- < Cl- < F- Soft acids bond in order of: F- < Cl- < Br- < I- Soft acids/bases are larger and more polarizable. Hard acids/bases are small and charge dense. Hard will tend to bond to hard, soft tends to bond to soft. How does covalence apply to HSAB? - correct answer(s) ✔✔ Use these as a rule of thumb, not a law.
- For a given cation, covalence increases as the size of the anion increases.
- For a given anion, covalence increases as the size of the cation decreases.
- Covalence increases as charge increases.
- Covalence is larger for non-noble configurations. What contributes to the Gibb's energy of complex formation, other than the type of bond formed? - correct answer(s) ✔✔ 1. Competition with solvent
Kw=[H3O+][OH-]. Kw= 1.0x10⁻¹⁴ (at 25°C), and we can define Ka and Kb in terms of Kw, allowing us to easily convert between the two. Ka Kb=Kw ∙ Discuss proton affinity and proton gain enthalpy. - correct answer(s) ✔✔ Proton affinity (AP) and proton gain enthalpy (ΔpgH0) relate acidity to enthalpy changes during a proton transfer. Proton gain enthalpy is reported as a positive number, and the proton affinity is the negative of it. A high AP indicates strong basicity, if only slightly negative, it is only weakly basic or possibly acidic. Proton gain can be described by these 3 steps:
- Electron loss from A-: A-(g) → A(g) + e-
- ΔegH⁰(A) = Ae(A) The reverse of electron gain by A
- Electron gain by H+: H+(g) + e- → H(g)
- ΔiH0(H) = -I(H) The reverse of ionization of H 3Combination of H and A: H(g) + A(g) → HA(g) -B(H-A) The reverse of H-A bond dissociation The proton gain enthalpy is the sum of the preceding enthalpy changes: ΔpgH0(A-) = Ae(A) - I(H) - B(H-A),
AP(A-) = B(H-A) + I(H) - Ae(A) What is the dominant factor in determining acid character? - correct answer(s) ✔✔ Electron affinity is the dominant factor. Electron affinity and proton affinity are inversely related, so observing the trend of Ae increasing from left to right, the proton affinity increases right to left. As proton affinity decreases, acidity increases, so Ae and stronger acid character have a positive, direct correlation. A higher Ae corresponds to a more stable conjugate base. Construct a Born plot for the thermodynamic cycle for a general proton gain reaction. (refer to picture in study guide for help) - correct answer(s) ✔✔ Refer to study guide. Discuss solvent levelling. - correct answer(s) ✔✔ Solvent levelling in water is the fact that any strong acid or strong base in aqueous solution is only as strong of an acid as H3O+ or as strong of a base as OH-. The relative strengths of strong acids can be measured by using an anhydrous weak acid as the solvent. The same idea can be applied to bases. What are the equations for Ka and Kb when considering the solvent levelling effect of water? - correct answer(s) ✔✔ Ka=[H₂Sol][A-]/[HA] Kb= [HB+][Sol-]/[B] How is the Bronsted definition of acids and bases extended by the solvent system definition? - correct answer(s) ✔✔ The Bronsted definition is only concerned with proton transfer. The solvent system definition defines an acid as any solute that increases the concentration of the cation generated by auto ionization of the solvent. It defines a base as anything that increases the concentration of the anion generated by the auto ionization of the solvent. Define and discuss aqua acids. - correct answer(s) ✔✔ The acidic proton is on a water molecule coordinated to the central metal ion. Acid strength increases as the covalent character of the M-O(H2) bond increases. Across the periodic table, covalence increases left to right, and top to bottom. Generally, the heavier the metal, the stronger the acid will be.
-Group 14: Except carbon, group 14 elements exhibit hypervalence and act as Lewis acids, tin(II) chloride acts as both a Lewis acid and base. -Group 15: Oxides and halides of the heavier elements act as Lewis acids. -Group 16: Sulfur dioxide can act as a Lewis base when it forms a complex with a trialkylamine that acts as a Lewis base. Sulfur trioxide is a strong Lewis acid. -Halogens: Bromine and Iodine act as mild Lewis acids. What's the difference between hard-hard and soft-soft interactions? - correct answer(s) ✔✔ Hard preferentially bonds to hard, soft preferentially bonds to soft. H-H and S-S are more thermodynamically stable than H-S or S-H. Soft-soft is more covalent in character, whereas hard-hard is more ionic in character. Factors influencing the Gibb's energy of complex formation:
- Competition with solvent
- Rearrangement of the substituents of the acid and base that may be necessary to permit formation of the complex
- Steric repulsion between substituents on the acid and the base Soft acid/soft base interactions tend to be exothermic Define reduction, oxidation, reducing agent, and oxidizing agent. - correct answer(s) ✔✔ Reduction: The gain of electrons Oxidation: The loss of electrons Reducing agent: the species which supplies the electrons (it is oxidized)
Oxidizing agent: the species which receives the electrons (it is reduced) Together, they make the redox couple. What is the significance of oxidation numbers? - correct answer(s) ✔✔ Oxidation are not tangible, or observable, they are merely a bookkeeping method. They are used to describe the ionic state of an atom. Why do we write half reactions to express reduction potentials? - correct answer(s) ✔✔ Because of the fact that in a redox reaction we are following the movement of electrons, breaking a reaction up into half reactions to separate reduction and oxidation gives us a clear view on the electron transfer, and simplifies balancing a reaction. When written as a complete reaction, the electrons cancel out, and are not written. Remember that all half reactions are written as reductions (in data tables, etc...), so the sign on the reduction potential may need to be reversed. Know how to charge balance a redox reaction. - correct answer(s) ✔✔ Example Problem: Balance redox reaction in acid solution: MnO4- + H2SO3 → Mn2+ + HSO4-? MnO4-(aq) + H2SO3(aq) -> Mn2+(aq) + HSO4-(aq) First, separate it into half reactions: MnO4-(aq) + 5e- + 8H+ -> Mn2+(aq) + 4H2O(l) Eo= +1.51V *This half reaction was obtained from a Latimer diagram. The Latimer diagram only shows the species which are present, the oxidation state, and the standard cell potential. You have to be able to figure out the number of electrons to add, and because the problem specified that it is in acid, how many H+ to add.
