University of Delhi 2010-1st Year B.Sc PMCS (Physics, Mathematics, Computer Science) Prog CHEMISTRY UNIVERSITY - Question Paper
This question paper contains 8 printed pages.]
Your Roll No . .
BJSc7B.Sc. (Hons.)/I/NS J
CH-103 - CHEMISTRY (NC - Admission of 2008 onwards)
Time : 3 Hours Maximum Marks : 75
(Write your Roll No on the top immediately on receipt of this question paper )
(Use separate answer-sheets for Sections A, B and C each)
SECTION-A (Inorganic Chemistry)
Attempt any two questions.
(m) The dipole moment value of NH3 molecule is higher than that of NF3, though the N - H bond is less polar than the N - F bond 2Vi
(iv) BaO is 2000 times more soluble than MgO, but BaS04 is insoluble, however MgS04 is
quite soluble in water 2Vi
(v) s-orbitals are spherically symmetrical 2Vi
(a) Write the time-independent Schrodinger wave equation for hydrogen atom and explain the physical significance of 'J'2. 2Vi
(b) Sketch the radial probability curve for 3s,
3p and 3d orbitals on the same set of axis. 2Vi
(c) What is the concept of multiplicity rule ? How do you justify the Hunds rule of maximum multiplicity *> 2Vi
(d) Justify which of the following orbitals are not feasible:
lp, 5f, 3g, 2d , 2Vi
(e) Draw the shapes 3d orbitals, indicating the sign of wave function 2Vi
(a) Draw the molecular orbital energy level diagrams for C2 and 02 molecules and explain the following
(l) Oxygen is paramagnetic (n) C2 molecule is diamagnetic
(111) The bond order in C2 is 2
(b) (i) State giving a reason m each case,
which cation will exert a greater polarizing power in the following cases :
(I) Na+ or Mg2+
(H) Cu2+ or Ca2+
(11) Of the following pairs of anions, which one will be more easily deformed 7 Give reasons
(I) C/ ~ or I ~
(II) O2" or F" 4
(c) Explain
(I) I" and XeF2 molecules have linear geometry. lYi
(II) Consider the hypothetical reaction
Na(s) + C/2(g) NaC/2(s)
Where the products contain Na2+ ions and Cl~ ions Estimate the heat of formation of NaC/2 from the following data by the use
of Bom-Haber cycle and comment upon its stability.
Heat of atomization of Na(s) = + 109 kJmoH Heat of atomization of C/2(g) = + 247 kJmol-1
Electron gam enthalpy for C/(g) = -349 kJmol~l Lattice enthalpy of NaC/2(s) = -2155 kJmor1
The first and second ionization enthalpies of Na(g) are +494 and + 4561 kJ mor1 respectively. 3
SECTION - B (Organic Chemistry) Attempt any two questions
4. Explain why 7
(1) a-Bromopropiomc acid is a stronger acid than p-Bromopropiomc acid
(n) Aniline is a weaker base than methyl-amine 0
(m) CH3CH2 is more stable than CH3CH
(iv) Isobutyl group is of highei priority than n-butyl group
(v) Glycerol has higher boiling point than n-propanol 2Vi x 5
5 * (a) Giving reasons arrange the following .
ch3ch2cooh(I)j hoch2ch2cooh(H), acaijCOOHan), ch3ch(c/)coohov)
and BrCHjCHjCOOHfV) in increasing order of acid strength. 4
(b) Which of the following possesses
aromaticity9 2
(c) Assign R or S configuration to any two of the following *
|
H' |  |
COOH |
|
HC = CH2 h3C | ||
(d) How many stereoisomers are possible for 2,
3 dichlorobutane 9 Write their configurations 2 Vi
(a) Distinguish between the following terms :
(i) Homolytic and Heterolytic cleavage
(ii) Enantiomers and diastereomers 3
COOH
(b) (l) HjNCH
1:h2oh
H
(ii)
HOH2C iCOOH ~NH2
What is the relationship between (i) and (n) Enantiomers or two orientations of the same molecule 7 2
r
\
(c) Giving reasons, arrange the following carbocations in increasing order of stability:
CH3, CH3-CH2, CH3-eCH-CH3
CH2
and
SYz
(d) Assign E or Z configuration to the following h2N\c = c/ CHO BrNc = Qs CH2C/
H3C/ nCH3 , BrH2C/ NC/ 2
SECTION - C Attempt any two questions Use of Scientific Calculators is allowed
1. (a) In which of the following systems is the energy of the system conserved in every process (1) a closed system, (11) an open system, (111) an isolated system, (iv) a system enclosed in adiabatic walls ? Justify your choice 2 Vz
(b) Does the first law of thermodynamics impose any restrictions on the direction of a process ? Explain 2
(c) Why is AU = 0 for every cyclic process 9 2
(d) Can the vapourisation of water at 100 C and 1 atm pressure be treated as a reversible process ? Explain 2
(e) How does the addition of excess NH4C7 in
addition to NH4OH prevent the
precipitation of Zinc hydroxide in a mixture of AI and Zn salt ?
(f) The indicator range of Thymol blue is 1 2 to
2 8 Will it be a suitable indicator for a strong acid-strong base titration ? Explain
8 (a) Calculate the work done when 1 mole of a monatomic ideal gas undergoes a reversible adiabatic expansion from 2 L to 4 L at 25 C. Molar constant volume heat capacity of the gas is 1.5 R. What would be the change in temperature if the expansion was against a constant external pressure of latm 7
(b) Derive the following equations :
(i) AS = R In V2/Vl for an ideal gas at
3P'
as
av
v
constant temperature
(c) Given the following AH298 values in kcal/mol.
Fe203(s) + 3C(s) 2Fe(s) + 3 CO(g) AH = 117
I
FeO(s) + C(s) Fe(s) + CO(g) AH = 37 2C0(g) + 02(g) -> 2C02(g) AH = -135
C(s) + 02(g) - C02(g) AH = - 94
Find the heats of formation of FeO and Fe203(s) 4 y2
9 (a) Show that the pH of a solution of a salt of strong acid and weak base is given by
pH = - 0 5 [log - log \'+ log C] 4
(b) Estimate the pH of a solution obtained by mixing 5 g of acetic acid and 7.5 g of sodium acetate m a J L standard flask and making it up to the mark Dissociation constant of the acid is 1 8 x 10-5 4
(c) Calculate the molar solubility of Pbl2 (i) in water and (n) in 0*200 "lit sodium iodide solution K$p of PbL, = 7 9 x 10-9. Ignore the amount of iodide coming from Pbl2 in the sodium iodide solution. 4Vz
5162 8 4,000
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