Indian Institute of Technology Kharagpur (IIT-K) 2008 M.Sc Chemistry Inorganic - Question Paper
INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR End-Autumn Semester Exam. 2008-,09 Inorganic Chemistry -CY20105(CY20103); Department of Chemistry No. of students: 5; Full marks: 50 ; Time: 3 hrs
Wee
OTLod6
fGive the expected hybridization of the central atom in each of the following:
C02, Hg(CN)2, S02, C032. 2 marks
Draw Lewis dot structure for NO3 , and give the contributing structures for its resonance hybrid structure. 1+ 2 marks
J) Using MO diagrams account for the differences in dissociation energies and bond lengths of the molecules given in the table 011 addition and removal of an electron.
6 marks
|
Molecule |
Bond energy, kJ/mol |
Bond distance (pm) |
|
n2 |
941.66 |
109.77 |
|
n2+ |
840.67 |
111.6 |
|
n2" |
765 |
119 |
|
02 |
493.59 |
120.75 |
|
02+ |
642.9 |
111.6 |
|
02- |
395.0 |
135 |
Although the oxidation state of Na and Mg in NaCl2 and MgO is +2 respectively, NaCh does not exist but MgO does. Explain this using the Born-Haber cycles and lattice energies. 2 marks
t Sketch the probability density function for the ground state orbital of the hydrogen >m. Indicate the Bohr radius and the most probable radius. 3 marks
jgf In sodium (atomic number 11) the value of the effective nuclear charge of the 3s1 electron is approximately two rather than the expected value of one. Why? 2 marks
Calculate Z* for one of the valence 4s electrons in the atom 3oZn using Slaters rules. 2 marks
8vBeS and NaCl have the closest packed lattice structures. Use radius ratio to predict in which holes do Be2+ and Na+ fit. Be2+ = 59 pm, S2_ =170 pm, Na+ =116 pm, Cr=167pm. 2 marks
9) (a) Sketch the bonding and the antibonding MO orbitals of H2 (indicate the symmetry and sign) (c) Write down at least two differences between them. 1+2 marks
UJ) Which are the Bronsted acids and bases in this reaction:
'HCl + NH3 -> NH4+ + Cl 2 marks
11) An electron pair donor would be an example of (1) a Lewis acid; (2) an Arrhenius acid;.) a Lewis base; (4) an Arrhenius base; (5) a Bronsted acid; (6) a Bronsted base; (7) a Usanovich acid; (8) a Usanovich base 1 mark
izf) Which of the following would describe a basic anhydride? (1) JaSO;
\2) Si02 (3) BaO; (4) H2SO4; (5) TiOj); (6) CaO; (7) P2Os; (8) C02V____2 marks
13) Identify the acids and bases in the following reactions? a) Ag+ + 2NH3 -> [H3N-Ag-NH3]+
+ O; --
bT "n
* * *
c) EtNa + Et2Zn Na+ + ZnEt3
dfi H2O + NH4+ -> H30+ + NH3 4 marks
J4) Although BF3 is normally a stronger acid than diborane, B2H6, the latter forms a compound with CO - that is, H3BCO - but the former does not. Why? 3 marks
/15) Predict all the products and explain why:
1) Me20BF3 + R3N -> ? 2 marks
W) Identify the following ions/molecules as hard acids, hard bases, soft acids and soft bases: CO, R>JH2* H+, R3P, U4+,pu+, R2S, HO 2 marks
J7) Write down the structure of the molecules: AlMe3, XeF4, B2H6, BrF5 2 marks
Predict the products of the following reactions:
jsl) BF3 and excess NaF in acidic aqueous solution J>) BCI3 and excess NaCl in acidic aqueous solution
c) BBr3 and excess NH(CH3)2 in a hydrocarbon solvent. 3 marks
Calculate -AH for the reactions of H+ with NH3 and H30+ with NH3. 2 marks
|
h3o+ |
Ea = 13.27 |
CA = 7.89 |
RA = 20.01 |
|
H+ |
Ea = 45.00 |
CA - 13.03 |
RA= 130.21 |
|
nh3 |
Eb = 2.31 |
CB = 2.04 |
Tb = 0.56 |
J2f)) In the valence bond theory, a) What is the wave function for H2 molecule b) Write down the canonical structures for H2 molecule. 2 marks
|
Attachment: |
| Earning: Approval pending. |
