Chemistry PU.C. First Year Midterm

Chemistry P.U.C. First Year Midterm Exam Notes

Part A: Multiple Choice Questions

• Non-polar molecule: CO2 is non-polar due to symmetrical linear structure.
• Order of repulsion: Lone pair-lone pair > lone pair-bond pair > bond pair-bond pair.
• Bond enthalpy definition: Energy required to break one mole of a bond in gaseous state.
• Carbon's properties: Catenation, isomerism, and tetravalency contribute to extensive carbon compound formation.
• Pent-2-ene consists of 14 sigma bonds and one pi bond.
• IUPAC naming options for organic compounds highlight practicality in nomenclature.
• Fractional distillation is applicable when there's a small difference in boiling points of liquids.

Part B: Short Answer Questions

• Law of multiple proportions: Different compounds formed from the same elements combine in ratios of small whole numbers.
• Pauli's exclusion principle: No two electrons in an atom can have the same set of four quantum numbers.
• Isoelectronic species: Atoms or ions with the same number of electrons; examples include Ne and F⁻.
• Elements with Z = 14 are situated in Period 3, Group 14 of the periodic table.
• Lewis symbols represent valence electrons, crucial for bonding information (O has 6, CO2 shows C=O double bonds).
• Polar covalent bond: Results from unequal sharing of electrons; example: HCl.
• Inductive effect involves electronic shifts through sigma bonds; resonance effect involves delocalization of electrons across multiple adjacent atoms.

Part C: Detailed Answers

• Ionization enthalpy decreases down a group due to increasing atomic size which reduces nuclear attraction.
• Na+ is smaller than Na because it loses a valence electron, reducing electron-electron repulsion.
• IUPAC name for element with atomic number 110 is Darmstadtium (Ds).
• Water molecule shape is bent according to VSEPR theory due to two lone pairs on oxygen influencing bond angles.
• Sigma bonds are formed by head-on overlap of orbitals while pi bonds form by side-to-side overlap.

Part D: Extended Answers

• Heterogeneous mixture consists of visibly different substances; example: salad.
• Scientific notation for 0.0048 is expressed as 4.8 x 10⁻³.
• Mole: quantity of substance containing the same number of entities as atoms in 12 g of carbon-12; molar mass: mass of one mole of a substance; sodium chloride molar mass is 58.44 g/mol.
• Characteristics of cathode rays include: they are negatively charged, travel in straight lines, and cause fluorescence.
• Limitations of Rutherford atomic model include lack of explanation for atomic stability and emission spectra; wave number unit: m⁻¹.
• Bohr's atomic model postulates include quantized energy levels, electron transitions result in electromagnetic emission/absorption, and energy levels correlate with principal quantum number.
• Quantum numbers (n, l, m_l) provide information on electron location, energy, and angular momentum in an atom.

Part E: Problem Solving

• Empirical and molecular formulas can be deduced through percentage composition and molar mass; utilize atomic masses for calculations.
• Molar mass of C2H5OH is 46 g/mol; percentage of C can be calculated based on mass contribution.
• Molarity formula involves moles per volume in liters; calculate using mass of solute and volume of solution for Sucrose.
• Wavelength and wavenumber calculated from the Balmer series formula for hydrogen spectrum transitions.
• De-Broglie wavelength from velocity of electron uses the formula λ = h/mv; implies wave-particle duality of matter.
• Energy of photons can be determined from frequency using Planck's equation (E = hν).
• Wavelength and wave number calculations for low-frequency broadcasts shows usage of electromagnetic radiation formulas.

Conclusion

Study these points for a solid understanding of P.U.C. First Year Chemistry, focusing on concepts, calculations, and definitions.

Test your knowledge with this midterm quiz for Chemistry PU.C. First Year. Covering essential concepts including molecular polarity and bond pair repulsion, this quiz is essential for students preparing for their exams. Challenge yourself and see how well you understand the key topics in chemistry.