CHY 142 Exam 1A Updated 2026

Exam 1A Updated Study Material CHY 142 2026 | Fully Updated Solutions What is electron geometry? - answer - Placement of bonding pairs and lone pairs in a molecule (tetrahedral) What is molecular geometry? - answer - Place of atoms only in a molecule (tetrahedral, trigonal pyramidal, bent) What are the electron geometries and their respective hybridization and angles? - answer - 2 electron pairs: linear (sp, 180°) 3 electron pairs: trigonal planar (sp², 120°) 4 electron pairs: tetrahedral (sp³, 109.5°) 5 electron pairs: trigonal bipyramidal (sp³d) 6 electron pairs: octahedral (sp³d²) What are the molecular geometries of each electron geometry? - answer - 2 electron pairs: linear 3 electron pairs: trigonal planar, bent 4 electron pairs: tetrahedral, trigonal pyramidal, bent 5 electron pairs: trigonal bipyramidal, seesaw, T-shaped, bent 6 electron pairs: octahedral, square pyramidal, square planar What is the degree of unsaturation formula? - answer - C - H/2 - X/2 + N/2 + 1 = number of rings/π bonds where X is a halogen (F, Cl, Br, I) What is molecular orbital theory? - answer - Molecular orbitals are formed by linear combinations of atomic orbitals, producing bonding and antibonding molecular orbitals that electrons can occupy (bonding MO: low energy, more stable antibonding MO: high energy, less stable) What is hybridization? - answer - mixing of atomic orbitals on the same atom to form hybrid orbitals What is a sigma bond? - answer - Head-on overlap of atomic orbitals along bond axis What is a pi bond? - answer - Sideways overlap of unhybridized p orbitals not on bond axis How many sigma bonds and pi bonds do single, double and triple bonds have? - answer - Single: 1 sigma, 0 pi Double: 1 sigma, 1 pi Triple: 1 sigma, 2 pi What is the relationship between bond order and length? - answer - Inversely proportional: inc bond order, decrease bond legnth What is the relationship between bond order and bond strength? - answer - Directly proportional: inc bond order, inc bond strength What is an s-character? - answer - The percentage an s atomic orbital contributes to a hybrid orbital Does sp³ or sp have a higher s character? Why? - answer - sp has a higher s-character (1 s & 1 p orbital, 50% s-character) sp³ has a lower s-character (1 s orbital & 3 p orbitals, 25% s-character) What are the 3 types of non-covalent interactions? What are they? - answer - 1. Ionic bonds: strongest, electrostatic attraction b/w ooppistely charged ions VAD DER WAALS: 2. Dipole-dipole interactions: attractions b/w polar molecules that align the partially positive end of one molecule with the partially negative end of another 3. London Dispersion forces: weakest, attractions caused by randomly induced dipoles/distribution in the electron cloud that induce a dipole in nearby molecules What types of non-covalent interactions are hydrogen bonds? What are they? - answer - Dipole-dipole interactions: covalently bonded with hydrogen and F, O, N, interaction with a lone pair on another F, O, N What does melting pt increase with? (3) - answer - 1. Strength of interactions 2. Molecular size (more electrons, greater polarizability, stronger LDF) 3. Molecular shape (greater surface area, more contact b/w molecules (more parts of electron cloud can interact), stronger LDF)) What is polarizability? - answer - How easily an electron cloud can be distorted, stronger temporary (self) and induced dipoles (other molecules), stronger LDF What is solubility? - answer - New interactions form between a solute and solvent in exchange for breaking the original interactions (like dissolves like) What's the difference between aldehydes and ketones? - answer - Aldehydes: -al, end carbons ONLY Ketones: -one, non-end carbons ONLY What's the difference between a phenyl and a benzyl as substituents? - answer - Phenyl: benzene ring directly attached to rest of molecule (aniline) Benzyl: CH2 group between benzene ring and rest of molecule (benzylamine) ORGANIC F