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LABRAKE CH301 Exam 4 Fall 2017
50090
Remember to refer to the Periodic Table handout that is separate from this exam copy. There are many conversion factors and physical constants available there.
NOTE: Please keep this exam copy intact (all pages still stapled - including this cover page). You must turn in ALL the mate- rials that were distributed. This means that you turn in your exam copy (name and signature included), bubble sheet, pe- riodic table handout, and all scratch paper. Please also have your UT ID card ready to show as well.
This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering.
001 10.0 points Which of the following ionic compounds has the largest lattice energy?
- MgS correct
- RbCl
- LiCl
- SrS
Explanation: Lattice energy increases as charge density in- creases (as ions get smaller and have a larger charge).
002 10.0 points Which of the following statements about the periodic trend of atomic radius is/are true?
I. Atomic radius decreases from left to right across a period because Zeff increases.
II. Atomic radius increases from left to right across a period because the number of valence electrons increases.
III. Atomic radius increases from top to bottom in a group because the number of electron shells increases.
- II and III only
- I only
- II only
- I and III only correct
Explanation: Atomic radius decreases from left to right across a period because Zeff increases, and in- creases from top to bottom in a group because the distance of the valence electrons from the nucleus increases.
003 10.0 points How many distinct resonance structures con- tribute to the overall structure of CO^23 −?
- 5
- 1
- 3 correct
- 2
- 4 Explanation:
004 10.0 points How many lone pairs of electrons are in the Lewis structure for CH 2 Br 2? (Be sure to count ALL lone pairs on the central atom and any surrounding atoms.)
- 6 correct
- 14
- 12
- 5
- 10
- 7 Explanation:
005 10.0 points Which one of the following name/formula combinations is NOT correct?
- rubidium oxide - RbO correct
- sulfur trioxide - SO 3
- calcium fluoride - CaF 2
- carbon tetrafluoride - CF 4
- magnesium sulfide - MgS Explanation:
- N correct
- They would have the same IE because they are in the same period.
Explanation: Elements which would require you to remove an electron from a half-filled or completely filled subshell (except for a half-filled s) have a higher IE than the normal trend would sug- gest.
011 10.0 points How many lone pairs of electrons are in the Lewis structure for HCN? (Be sure to count ALL lone pairs on the central atom and any surrounding atoms.)
- 0
- 2
- 1 correct
- 4
- 3
Explanation:
012 10.0 points Name the following polyatomic ion: ClO− 2
- chloride
- chlorite correct
- chlorate
- hypochlorite
- perchlorate
Explanation: ClO− 2 is chlorite.
