Chemistry 101 Exam III Notes

Exam Overview

• Course: Chemistry 101
• Exam Date: December 5, 2024
• Exam Length: 1 hour and 30 minutes
• Total Questions: 17 (15 Multiple Choice, 2 Free Response)
• Total Points: 60 (30 pts for questions 1-15, 12 pts for question 16, 18 pts for question 17)

Part 1: Multiple Choice Questions

Question 1: Exothermic Processes

• Exothermic processes release energy to the surroundings.
• Processes Listed:
  • Water freezes to become ice (exothermic)
  • Hydrogen and oxygen react to form water vapor (exothermic)
  • Mixing two solids causing cooling (endothermic)
  • Racquetball hardening in liquid nitrogen (endothermic)
• Answer Choice: 2 exothermic processes.

Question 2: Atoms and Energy

• True Statements:
  • Exothermic and endothermic processes may require activation energy to begin.
  • Exothermic means energy is released.
• False Statement: Products are lower in energy than reactants in endothermic processes.

Question 3: Model of the Atom

• Key element: Positively charged nucleus at the center.

Question 4: Orbitals and Atoms

• Orbitals predict where electrons are found most often, not their specific locations.
• Orbitals become more complex closer to the nucleus.

Question 5: Ground State Configurations

• Correct pairing of ground state electron configurations for neutral atoms versus their ions is crucial.

Question 6: Bond Polarity Ranking

• Options ranked from least polar to most polar involve understanding electronegativity difference and bond types.

Question 7: Atomic Size

• Compare neutral atoms for size; knowledge of periodic trends (atomic radius increases down a group).

Question 8: Ionization Energy

• Trends indicate the first ionization energy is inversely related to atomic size.

Question 9-12: Lewis Structures

• Draw structures for compounds IF3, PCl5, NH3, CH2O, H2O, OF2, SO2, CO2.

Question 13: Resonance Structures

• SO2 requires resonance structures due to multiple valid Lewis structures.

Question 14: Atomic Radius Comparison

• P3- is larger than neutral P due to electron-electron repulsion in the ion.

Question 15: Energy to Remove Electrons

• Removal energies differ in Ne vs. Mg2+ due to nuclear charge differences affecting electron-nucleus attraction.

Part 2: Free Response Questions

Question 16: Identifying Elements

1. Neutral ground state configuration [Ar]4s23d104p4 - Identify element (Te).
2. Most electronegative of three unpaired in period 3 - Identify element (Cl).
3. Trigonal pyramidal resulting from hybridization - Identify element (N).
4. Alkaline earth with 8 in the third level - Identify element (Mg).
5. Even sharing with oxygen - Identify element (C).
6. Excited state configuration 1s22s22p63s23p34s13d2 - Identify element (Sc).

Question 17: Molecule Comparison

• Set 1: Draw Lewis structures for hydrocarbons (C2H2, CH2CHF, CH3CH2OH), determine shapes, polarity, and rank boiling points based on intermolecular forces (dispersion forces vs hydrogen bonding).

• Set 2: Analyze central xenon compounds (XeCl2, XeF2Cl2): draw structures, determine shapes, polarity, and rank boiling points based on the presence of polar bonds and molecular geometry.

Important Concepts to Review

• Exothermic and Endothermic Reactions: Understand these concepts and their definitions.
• Periodic Trends: Knowledge of atomic radius, ionization energy, and electronegativity trends is necessary.
• Resonance Structures & Molecular Geometry: Familiarize with drawing and interpreting Lewis structures, VSEPR theory, and concepts of molecular polarity.
• Intermolecular Forces: Know types (hydrogen bonding, dispersion, etc.) and their influences on state and physical properties of substances.