AP Chemistry: Class 25

Arrrrr, maties!

Period E – Friday, October 18th

Big Ideas from Chapter

• Energy is conserved
  • First law of thermo (ΔU = Q + W)
  • Defined: internal energy, work, heat, thermal energy
  • Defined: system, surroundings
  • Why? stapler = favorite object
• Enthalpy is a measure of energy content
  • ΔH is part of any process
  • examples: combustion, solvation, formation, reaction
  • ΔH can be added for reactions (Hess’s Law) just like in math class
• Calorimetry is a way to measure energy changes
  • ΔH = Q @ constant pressure (any experiment conducted in classroom)
  • energy flow into or out of water is key to the process
  • Q = msΔT
  • Calorimeter can absorb energy (Q = CΔT)

Practice Problems

• Suggested textbook practice: Ch. 5 (62, 65, 66, 73)
• Old exam questions posted (Lecture & Content Folder)

Exam

• Three work-em-out questions
• 1st question = 1st Law of Thermodynamics
• 2nd Question = enthalpies of reactions and Hess’s Law
• 3rd question = calorimetry
• Also: Naming & Katie Lim

Homework

• Study for Exam
• Study session Sunday @ 5:00 pm (Homer 226)

LAB ANSWER

You cannot determine the identity of the carbonate because the calcium chloride is the limiting reactant in the reaction. Gravimetric analysis only works when the precipitate is tied to the desired limiting reactant.