The Union Public Service Commission (UPSC) holds the Civil Services Examination every year in two parts, i.e. Preliminary Test and Main Examination; the Main Examination comprises a written Test and a Personality Test. The Question paper of the IAS Main Chemistry Paper I –2010 is given below:

**CHEMISTRYPAPER-I**

**Time Allowed: Three HourseMaximum Marks: 300INSTRUCTIONS**

Each question is printed both in Hindi and in English.

Answer must be written in the medium specified in the Admission Certificate issued to you, which must be stated clearly on the cover of the answer-book in the space provided for the purpose. No marks will be given for the answers written in a medium other than specified in the Admission Certicate.

Candidates should attempt Question Nos. 1 and 5 which are compulsory, and any three of the remaining questions selecting at lest one question from each Section.'

The number of marks carried by each question is indicated at the end of the question.

Symbols and notations carry usual meaning, unless otherwise indicated. Coordinate diagrams, wherever required, may be plotted on the answer-book itself. Assume suitable data if Considered necessary and indicate the same clearly.

**Section-A**

**1. (a)** Deduce the following equation for a partice in a one- dimensional box giving the Hamiltonian explicitly: ?

ψn=Asin(n∏x/a)

Also decuce the energy for the system. ** 15****(b)** Using VSEPR theory, predict the shapes of PCL2 F3 and SF4 . Indicate the State of hybridisation in each case. **15****(c)** How do you account for the fact that the rate of reaction is more than double for a ten degree rise of temperature, whereas the number of collisions increases by only 3-4% for the same rise of Temperature ? **15****(d) **What are meant by phase, component and degree of freedom? Define Gibbs phase rule.

A saturated solution of sodium sulphate with excess salt is at equilibrium with its vapour ina close vessel. How many phases, components and degrees of freedom are there in the system ? ** 10+5****2. (a)** Draw the MO energy-level diagram for N2 and o2 molecules. Predict their magnetic behaviours and also calculate the bond orders.**(b) (i) **State the essential conditions for hybridisation.Show diagrammatically the possible geometries from hybridisation of s, p and d orbitals. Give examples. **10****(ii)** Half- change time and initial concentrations of a reaction are as follows:

**t _{1/2}(sec) a(mm of mercury) 425 354 275 540 941 158**

What is the order of the reaction ? Calculate the rate constant.

**10**

**(c)**Lindemann's mechanism for the first- order reaction is given as follows:

Under what condition will be reaction show(i) first order and (ii) second order ? 20**3. (a)** (i) A photochemical reaction with quantum efficiency of one shows no temperature dependence. Explain. **10****(ii) **Calculate the number of moles of HCL(g) produced by the obsorption of one joule of radiant energy of wavelength 480 nm in the reaction

**H2(g)+ Cl2 (g)?2Hcl(g)**

if the quantum yield of the photochemical reaction is
**1.0×10 ^{6} . 10**

(b) Give the postulates on which Langmuir's adsorption isotherm is based. Derive the expression for Lamngmur's adsorption isotherm. How does this equation account for the adsorption at (i) high pressure and (ii) low pressure ?

Show that when a diatomic gas solid, the Langmuir adsorption isotherm is modified to where,

**Ø= fraction of surface covered**

K= k adsorption/k desorption

p= Presure of gas 20

K= k adsorption/k desorption

p= Presure of gas 20

**(c)**With proper diagram, calculate and explain briefly the limiting ration values for tetrahedral and octahedral sites.

**20**

**4. (a)**Draw the phase diagram of a simple eutectic system. Give an example of such a system.

**20**

**(b)**Using the principle of LCAO, obtain the normalised wave functions for the bonding and the antibonding molecular orbitals for H+2 system.

**20**

**(c) (i)**For the reaction

2NO+O2→2NO2

rate= k[NO]2 [O]2

Explain that the rate of this reaction decreases with increase of temperature. **10****(ii) **How much will the rate of reaction change if volume of the vessel is reduced to 1/3 of its original volume ? 10

**Section-B**

**5.(a)** What are interhalogen compounds? How are they classified ? Give structures of IF5 and IF 7. ** 15****(b) **How do you explain the magnetic properties of transition metal ions, Ln3+ by the Crystal Field Theory ? **15****(c) **Expalin what are meant by extensive and intensive properties of a system. Which of the following properties are extensive and which are intensive ? **15****(i) **Entropy**(ii)** Gibbs free energy**(iii) **Viscosity**(iv)** Chemical potential**(v) **Heat capacity**(d) **What is meant by liquid-junction potential ? Why is KCL salt bridge used to eliminate it ?

Give one example of a concentration cell with transference. **15****6. (a)** What is meant by heat capacity ? Establish a relationship between heat capacity at constant pressure and constant volume ,i.e.

Cp-Cv=[p+(ðE/ðV)T](ðV/ðT) p

Deduce the relationship for an ideal gas. **20****(b) (i) **Derive Bragg's equation and show that n?=2dsinØ for the reflection of X-rays from the faces of a crystal.

(ii) Calculate the interplanar spacing (d-spacing) in cubic crystal if the second - order refelctions from such planes are obtained.

sinØ= 0.38, when X-rays of λ 154 pm are used. **20****(c) **Discuss the different types of isomerism exhibited by coordination compound. Give suitable examples. ** 20****7.(a) (i) **What is Nernst equation ? Explain the various terms involved. ** 5**

**(ii) **Calculate the potential of the following cell. Write down the cell reaction and indicate the polarities of the electrodes: ** ****10****(b)** Find the expression for CFSE of d5, d6 and d7 systems in weak and strong octahedral fields in terms of Dq and P(pairing energy).** 20**

**(c) **What is the effect of temperature on the vapour pressure of a liquid ? Derive Clapeyron-Clausius equation for the equilibrium between liquid (Image) vapourGive the intergrated form of this equation. **15****(d)** Write IUPAC names of the following: **10**

**8. (a)** **(i)** Give a short account of S-N compounds. **10**

**(ii) **Why are 5f elements important? 5

**(b) (i)** Distinguish between chemical cell and concentration cell giving examples. **5**

**(ii) **Derive an expression for the e.m.f of electrode concentration cell without transference. ** 12**

**IAS Main Chemistry Question Paper II- 2010**

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