MSCE Chemistry flashcards
MSCE Chemistry · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Aufbau principle
- Electrons fill the lowest-energy orbitals first in the order 1s 2s 2p 3s 3p 4s 3d 4p, following the (n+l) rule.
- Effective nuclear charge
- The net positive charge an outer electron experiences after core shielding; Z_eff rises across a period, shrinking atomic radius and raising ionization energy.
- Hund's rule
- Within degenerate orbitals, electrons occupy separate orbitals with parallel spins before pairing, maximizing total spin and minimizing electron repulsion.
- VSEPR theory
- Electron domains around a central atom repel and arrange to minimize repulsion, predicting molecular geometry from the number of bonding and lone pairs.
- Formal charge
- Valence electrons minus nonbonding electrons minus half the bonding electrons; preferred Lewis structures place formal charges near zero on appropriate atoms.
- Hydrogen bonding
- A strong dipole-dipole attraction between H bonded to N, O, or F and a lone pair on a nearby electronegative atom; explains water's high boiling point.
- Bond order (MO theory)
- Half the difference between bonding and antibonding electrons; higher bond order correlates with shorter, stronger bonds.
- Limiting reagent
- The reactant that is completely consumed first, determined by dividing moles by stoichiometric coefficient; it sets the maximum product yield.
- Molarity
- Moles of solute per liter of solution; dilution follows M1V1 = M2V2, and molarity is temperature-dependent because volume changes with temperature.
- Empirical formula
- The simplest whole-number ratio of atoms in a compound; derived from percent composition, while the molecular formula is a multiple of it.
- Ideal gas law
- PV = nRT relates pressure, volume, moles, and absolute temperature; R equals 0.08206 L·atm/mol·K or 8.314 J/mol·K.
- Hess's law
- The total enthalpy change of a reaction is independent of pathway; standard enthalpies of formation can be summed to calculate reaction enthalpy.
- Gibbs free energy
- ΔG = ΔH − TΔS; a negative value indicates a spontaneous process at constant temperature and pressure, while zero indicates equilibrium.
- Calorimetry
- Measurement of heat exchanged using q = mcΔT for solutions or q = C_cal·ΔT for a bomb calorimeter; signs follow the system's perspective.
- Le Chatelier's principle
- A system at equilibrium shifts to counteract a stress such as concentration, pressure, or temperature change, restoring a new equilibrium position.
- Henderson-Hasselbalch equation
- pH = pK_a + log([A⁻]/[HA]); it calculates buffer pH and shows buffering is best when pH is near the pK_a.
- Solubility product
- K_sp is the equilibrium constant for dissolution of a sparingly soluble salt; comparing the ion product Q to K_sp predicts precipitation.
- Amphoteric species
- A substance that can act as either an acid or a base, such as HCO3⁻ or water, depending on the other reactant present.
- First-order kinetics
- Rate depends on one reactant concentration; ln[A] = ln[A]0 − kt, and half-life equals 0.693/k, independent of starting concentration.
- Arrhenius equation
- k = Ae^(−Ea/RT); raising temperature or lowering activation energy increases the rate constant exponentially.
- Nernst equation
- E = E° − (0.0592/n) log Q at 25 °C; it adjusts cell potential for nonstandard concentrations of reactants and products.
- Faraday's law of electrolysis
- The amount of substance deposited is proportional to charge passed: moles of electrons = It/F, with F = 96485 C/mol.
- SN2 mechanism
- A one-step bimolecular substitution with backside attack by nucleophile, second-order kinetics, and inversion of stereochemistry at the carbon.
- Markovnikov's rule
- In HX addition to alkenes, hydrogen adds to the carbon with more hydrogens, placing the more stable carbocation intermediate on the other carbon.
- Aromaticity (Hückel rule)
- A cyclic, planar, fully conjugated system with 4n+2 π electrons is aromatic and unusually stable, as in benzene with six π electrons.
- Beer-Lambert law
- A = εbc states absorbance is proportional to concentration and path length; it underpins quantitative UV-Vis spectroscopy using calibration curves.
- Retention time
- The time from injection to detection of a compound in chromatography; it identifies analytes under fixed conditions, while peak area quantifies them.
- Chemical shift (NMR)
- The position of an NMR signal in ppm, reflecting the electronic environment of a nucleus; deshielding by electronegative groups shifts signals downfield.
- Crystal field splitting
- Δo is the energy gap between d orbitals in a ligand field; strong-field ligands cause low-spin complexes with larger splitting.
- Chelate effect
- Multidentate ligands form more stable complexes than comparable monodentate ligands because complexation increases the entropy of the system.
- Safety Data Sheet
- A 16-section document required by GHS that covers hazards, first aid, handling, exposure controls, and disposal information for a chemical.
- Chemical hygiene plan
- A written program required by OSHA covering safe procedures, engineering controls, PPE, training, and medical consultation for laboratory workers.