CHEMISTRY PAPER 1 2000


Time Allowed: 3 hours Maximum Marks: 300
Candidates should attempt Question Nos. 1 and 5 which are compulsory, and any three of the remammg questions selecting alleasl one question from each Section Assume suitable data 1£ conSidered necess3lY and mdieale the same clearly

SECTION A
Answer any three of the folloWlng
Explain the difference between Is and orbitals and also between and 2p orbitals
What is the node in an atomic orbital and what role does it play in determining broadly the relative stability 0f various types 0f atomic orbitals with the same principal quantum number?
What is the bond order in CO molecule according to the molecular orbital theory. Also describe how the theory.explains coordination through carbon and negligible dipole moment of the molecule
Apply molecular orbital theory to explain paramagnetism of molecule

2. EO (Standard state pH for the electrode reaction CH3CHO 2H+ 2e- CH3CH3OH lS -0.197 volt. Calculate E at pH 6 when ethanol and acetaldehyde are present at 10.5 temperature 25°C

What changes do you expect in a cathodic polarogram lf the d.me lS replaced with some solld stationary electrode while solution conditions remain the same? Also explain why

State and explain the law of corresponding states. For large number of substances, the quantity RTc/Pc Vc lies between 3.4 and 3.7. Comment on the fact

3. Employing d.m. e. as the lndicator electrode, sometimes lt is possible to estimate a very dilute solution of some metal lon amperometncally even when there is no apparent chenucal interaction between it and the titrant Elaborate the statement taking an example

What lS an electrometric indicator and how does it facilltate the amperometric estimation of some metal speaes at d.m.e. Give an example

lons when titrated with Cr2O7-2 amperometrically at d.m.e at 00 Vm an aCldicmedium, yleld a curve which shows only non-f aradic current in the begmll1ng and faradic current appears (and then mcreases regularly as the titration progresses) only after the null pomt has been reached. however, a V-shaped curve is obtamed when the same titration is camed out at-1.2V Explain why it is so

4. Radius ratio of two types of lons is the determining factor for the ultimate crystal structure Elaboratethe statement taking examples of NaCI, BeD and CsCl [Ionic radii values is 0.98, 0.30 1.67: O2- 1.45: cL- 1.81]
Explain the crystal structure of Cd I2
A unit cube in the sodium chloride crystal contains 14 chlorine and 13 sodiumions and yet it contains four' molecules 0f NaCl Explain



SECTION II

Answer any three of the folloWlng

5. Ni(CO)4 contaINs metal IN zero-valent state and yet it lS quite stable Why?
Lantharudes are responsible for the extreme Similarity IN the chenuslly of zlrcoruum and hafnium and also for the fact that thm separation from each other has been a difficult task Conunent

Lantharudes have little tendency to fonn complexes but when they form they can allam high coordination number of7 or 8 even. Comment

Lantharudes have little tendency to fonn complexes but thE compounds are generally brilliant!y coloured. Any explanation?

6. How many bands are expected IN the electroNIc spectrum 0f and why?

Explain, applying crystal field theory, why lS easily oXldized to

Furnish explanation for the general inertness of square planar complexes of Pd and PI

7. What role photo sensitizers can play in the decay of photo -excited states? Explain Wlth an example(20)

How is phosphoros cencel important in the decay of some photo chemlcally excited molecules? Explam

What is the explanation for FeCl4-and HgI43-being tetrahedral on the baSiS of crystal field theory?

Explain the following facts from 'the standpoint of adsorption properties of reactant and product molecules

Decompos1tion of NH3 on W 1S zero order

Decomposition of N2O on Au lS first order
Recombination of H atoms on Au lS second order

A certain reaction lS 20% complete in 15 minutes at 40 °c and in 3 minutes at 60 Estimate lts activation energy

Show that for a first-order reaction the time required for 99.9% of reaction to take place lS ten times 0f that required for one-half the reaction