Schedule Today (2/18): Begin Chapter 7 Should have read Sections 7.1-7.4 (at least) New OWL assignments open See new text assignments (Course Information) Wednesday (2/20): Continue Chapter 7 Read Sections 7.5-7.6 (at least) Friday (2/22): Continue Chapter 7 Read Sections 7.7-7.9 (at least) Monday (2/25): Finish Chapter 7 Start Chapter 8 on Wednesday, 2/24

Exam 22c & Ch 14 #54 (OWL) 22. c. Like NO, the OH radical is a heteronuclear diatomic, but the atoms are quite different (more so than N and O). We consider the overlap in orbitals to form the MOs in OH to be between the 1s orbital of the hydrogen atom and one of the 2p orbitals of the oxygen atom.   i. Why does the hydrogen 1s orbital overlap with only one of the oxygen 2p orbitals? Does the overlap form a sigma(σ) or pi (π) bond? Use pictures in your explanation to show how the hydrogen 1s orbital interacts with the three oxygen 2p orbitals and why only one allows for overlap. [4 points] ii. Draw the appropriate relative molecular orbitals on the diagram below and label each with either b for bonding, a for antibonding, or n for nonbonding. Fill in the appropriate number of electrons (for both atomic and molecular orbitals). [4 points]

Question 21b 21. b. Retinal is a molecule found in the photoreceptor cells of the retina and is crucial in our vision by allowing us to convert visible light into a chemical signal in the brain. The structure of retinal is: i. Determine the longest wavelength of light that can be absorbed to cause a ground state electron to go to its first excited state. Assume the average carbon-carbon bond length is 140 pm and the average carbon-oxygen bond length is 120 pm. Include an appropriate and filled-in energy-level diagram (like the one given in part a). Justify the number and placement of the arrows. Show and explain all work. [8 points]

Consider two samples of pure water at different temperatures. The pH values are different. The pH values are the same. One sample is more acidic than the other. A B The samples are both neutral. C D

Clicker Question You add 1.00 x 10–12 mol of HCl to 1.0 L of water at 25°C. What is the pH of the solution? a) 2.00 b) 6.73 c) 7.00 d) 12.00 e) 14.00

Acid-Base Models Arrhenius BrØnsted-Lowry Lewis Acids produce hydrogen ions in aqueous solution Bases produce hydroxide ions in aqueous solution BrØnsted-Lowry Acids are protons (H+) donors Bases are proton acceptors Lewis Acids are nonbonding electron pair (lone pair) acceptors Bases are lone pair donors

Arrhenius Acid-Base Model Simple model Explains many of inorganic (general chemistry) acids and bases in aqueous solutions Acids: HCl, HNO3, H2SO4, H3PO4, HC2H3O2, “HA” Bases: Hydroxides: NaOH, KOH, etc. Problems: Limiting (aqueous solutions) Doesn’t couple acids and bases (HA → H+ + A–)

BrØnsted-Lowry Acid-Base Model Includes all acids and bases from Arrhenius model Better to discuss acid-base reactions/non-aqueous HCl and H2O: HCl and NH3: H2O and H2O: NH3 and NH3:

Lewis Acid-Base Model Includes all acids and bases from previous models. Systematic way of viewing reactions (all involve electrons: redox are transferring electrons, acid-base are sharing of electrons)

BrØnsted-Lowry Acid-Base Model  

Acids Vary in Strength

Acids Vary in Strength