1. Be respectful – no electronics please!
Announcements
What was the best thing about spring break?
Sleeping in
No homework
Seeing family
All of the above (pick this answer )
Pre/post lecture assignments due as usual Tuesdays & Thursdays at 8:00 am
Textbook homework due Friday in discussion
Liquid nitrogen winner is…

2. Exam 2 Commonly Missed Questions
#16 Set 2
Solution C consists of a 1.0 L aqueous solution of calcium hydroxide.
Solution D consists of a 1.0 L aqueous solution of hydrochloric acid (HCl)
Solutions C and D are combined together.
Give the balanced molecular equation for this reaction, showing all phases.
Ca(OH)2(aq) + 2HCl(aq)  H2O(l) + CaCl2(aq)
When these solutions reacted, they reacted in a perfectly stoichiometric ratio; neither reactant was in excess and both reactants ran out at the same time. Which solution had a higher concentration, solution C or D? Explain your answer.
Solution D had a greater concentration. Every time 1 mole of calcium hydroxide was used up, according to the balanced equation, twice as many moles of hydrochloric acid were used up. Therefore, if adding two solutions of volumes 1.0 L together resulted in a perfect stoichiometric ratio reaction, this means that there must have been twice as many moles of HCl present in the 1.0 L container as calcium hydroxide moles present.

3. Consider a substance, which can exist in multiple phases: in terms of particle movement…
Which phase has highest energy?
A solid
A liquid
A gas
All the same
Which phase is most stable?
A solid
A liquid
A gas
All the same

4. Clicker #1
Is a racquetball frozen by liquid nitrogen an endothermic or exothermic process? (The system is underlined.)
A) endothermic
B) exothermic

5. Clicker #2
Is the boiling of water an endothermic or exothermic process? (The system is underlined.)
A) endothermic
B) exothermic

6. Clicker #3
Ba(OH)2·8H2O(s) + 2NH4SCN(s)  Ba(SCN)2(aq)+ 2NH3(g)+ 10H2O(l)
Is the reaction of the two solids in the beaker an endothermic or exothermic process?
A) endothermic
B) exothermic

7. Clicker #4 Which is lower in potential energy? H2/O2 or H2O A) H2/O2
B) H2O

8. Clicker #5
Which is more stable?
H2/O2 or H2O
A) H2/O2
B) H2O

9. Overall goal: Atomic Structure Chemical Bonding 3D Molecular Structure
Molecular Properties