Exam Instructions and Guidelines

• Exam allows one 8.5 x 11 inch paper with handwritten notes on both sides.
• Use of a graphing or scientific calculator is permitted, but phones or other electronic devices are not allowed.
• Questions will not be answered due to different exam locations.
• No talking or communication is allowed once distributed.
• Exams are scanned and uploaded to Gradescope for assessment; graded exams are returned via email.
• Regrade requests are required electronically through Gradescope within one week after grades are released.
• The entire exam will be regraded.
• Answer keys will be posted once exams are returned.
• For open-ended calculations, work must be shown in the space provided with clearly marked answers and proper units.
• Answers should have appropriate significant figures, avoiding rounding during calculations.
• Partial credit will be given for open-ended questions if work is shown and legible.
• Duke Community Standard applies to all endeavors; honesty and integrity are expected.

Determining Molecular Polarity

• Molecules with a net dipole moment are polar, examples from the test are CF4, CH3I, CH2Cl2
• Lewis Structures are used to show the direction of the net dipole moment.

Isomerization of Cyclopropane

• Cyclopropane rearranges into propene when heated
• The rate constant for this reaction is provided on the test is 5.95 x 10-1 s-1 at 499°C.
• Half-life and fraction remaining are calculated based on this rate constant.

Cis-trans Isomers

• Cis-1,2-dichloroethene has a dipole moment, while trans-1,2-dichloroethene does not.
• Dichloroethene cannot interconvert between the two forms and exists in the configurations shown on the test

Reaction Rates of Decomposition

• The reaction provided on the test is 2 N2O5(g) → 4 NO2(g) + O2(g).
• How to express the reaction rate in terms of NO2 formation.
• Calculation of average reaction rate is shown on the test using given concentration changes over a time interval.

Potential Energy Diagrams

• Potential energy diagrams can represent endothermic and exothermic reactions.
• In exothermic reactions, products have stronger bonds than reactants
• In endothermic reactions, reactants must gain potential energy to convert to products.

Molecular Orbital Theory

• How To determine the number of unpaired electrons and paramagnetic properties of species like O2, F2, and OF is assessed on the test
• HOMO and LUMO identification for O2.
• Assessment of bond enthalpy among the species.
• Verification of bond orders calculated using MO theory with those predicted by Lewis structures.

Reaction Order Determination

• 1,3-Butadiene (C4H6) reacts to slowly form products above room temperature.
• The concentrations of C4H6 were measured at 326°C.
• Graphs of [C4H6], ln[C4H6], and 1/[C4H6] versus time are used to determine the reaction order.

Rate Law Determination

• Nitrogen monoxide reacts with chlorine: 2 NO(g) + Cl2(g) → 2 NOCl(g)
• Initial rates of reaction are observed for reactant concentrations.
• Determining rate law that describes rate dependence on NO and Cl2 concentrations.
• Calculation of rate constant with appropriate units.
• Rate calculation for given concentrations of NO and Cl2.

Molecular Structure and Hybridization

• Questions involve the hybridization of carbon atoms within a given molecule.
• Focus on bond angles, unhybridized p-orbitals, and types of bonds formed.
• Determine hybridization of carbon with tetrahedral molecular geometry.
• Identify bond angles and unhybridized p-orbitals around the carbon atom.
• Identify sp² hybridized carbon(s) and determine the electron pair geometry around sp² hybridized central atoms.

Bond Enthalpy

• Bond enthalpy calculation using provided enthalpy data, as shown in the question on the lest
• Formula N2(g) + 3 F2(g) → 2 NF3(g) ∆Hrxn = -103 kJ/mol for calculating the N-F bond enthalpy needs to be memorized

Reaction Mechanisms

• Determining the number of steps in a reaction mechanism and identifying the rate-limiting step using a reaction profile.

Lewis Structures and Formal Charges

• Writing Lewis structures and assigning formal charges for cyanate and fulminate ions.
• The central atom in OCN- is C, and in CNO- is N.
• Each ion has three resonance structures.
• Identification of the most representative structure for each.
• Comparing the representative resonance structures to explain why the cyanate ion is more stable than the fulminate ion.

This document outlines the rules and instructions for an upcoming exam. It covers permissible materials like handwritten notes and calculators, and prohibits unauthorized devices. It also details submission, grading, and regrade request procedures, emphasizing adherence to the Duke Community Standard.