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Unformatted text preview: CHEM 20A Lecture Section 1: Fall 2007, 1St Hour Test
Friday, October 19 NAME SOLUTMNI‘
TA USEFUL INFORMATION: Atomic weights: 137.3 (Ba), 35.45 (C1), 1.008 (H), 32.07 (S), 16.00 (0)
so = 8.854 x 10‘12 CZ/J—m e = 1.602 x 10'19 C N Av = 6.022 x 1023/mole problem points possible points scored
1 30
2 4O
3 30 TOTAL 100 BE SURE TO SHOW ALL YOUR REASONING... 1. (30 points) The reaction of BaCl2 with H2804 gives BaSO4 and HCl. Suppose we start with 4.35g of
BaCl2 and 3.36g of H2804, and the reaction is allowed to go to completion, i.e., until one of the reactants is
all used up. What is the amount of each compound that remains? 0125 of ‘ 4/ 35.9 ,_, 0 01¢? W5
M  ! [Iii3+ 2"(35‘fgﬂ‘erCn—
Boldlymazﬁ W / 54W“ 0.02.09 M645 of Bart—Q1 rdmuf" ,t frag“);
74'mw 560,erc GH/‘F’OLLMJ For Freda1.4.4!" £1 M2) 6km 6.92‘5‘7 W of £950? wa/mhud M 2. (40 points) Consider the bond associated with the imaginary diatomic molecule LM, Where the atom L
is much less electronegative than atom M. In particular, the ionization energies of L and M are 325 and
1510 kJ/mole, While the electron affinities are 45 and 300 kJ/mole. The equilibrium bond length is 1.64A.
(a) Let’s take into explicit account the fact that the LM bond is not completely ionic, but rather only 90%
ionic. Estimate the bond dissociation energy, i.e., the energy required to pull the molecule apart into separated L and M. M 9009 1% © ohmic W‘— W Maw (Mowe e/ecwvﬁ,) A5 4“: ' ﬂ —[IE(L)— HAW)
’" 47% (c) What is the ionization energy of the singly—charged ion, M? fE[/Vl‘) I: My“! 1:7 AE for M'——>/\4+e
Ewe ka 45 ,5 M1. of éwjgw M+c _.,., M’ L
AM 5/401) M MM. 63 ear for M+e am— /’ $E[/Vl‘)= EA (M) (’300 ,{f/Mo‘z‘ 3 3. Work out the Lewis diagram for IF4+ and use the Valence Shell Electron Pair
Repulsion (VSEPR) Theory to predict its molecular structure. +3 N bean4! =34 N =5x8 =90
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47‘ II}: 5M4 9'51wa FGMWU 39 8 walk :5
044 W PMS] Q: 53; p, (sq.4411, F M 2 <35 (/5'nfbb/a'm PW>MI \ g7w10rtonKV€ aged
foét'é'a‘w7 {:0 L/o—Nﬂ rel—7 2/ CV5 3) ‘70 Meiji“), ...
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