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…

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.

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

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

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

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

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

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

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