CSS past paper

CSS Chemistry Paper I Past Paper 2023

CSS Chemistry Paper I 2023 carries 100 marks over 3 hours. It has 7 questions.

Marks: 100
Time: 3 hours
Questions: 7

Years

How to attempt: Attempt ONLY FOUR questions from PART-II. ALL questions carry EQUAL marks.

Questions

Question 1 (Part I) is the paper's MCQs, which are not reproduced here.

Q. 2
(20)
- (a)
  The following reaction occurs via two steps, where the first step is rate-determining step.
  (12)
  Step I $\ce{NO2(g) + NO2(g) -> NO(g) + NO3(g)}$
  Step II $\ce{NO3(g) + CO(g) -> NO2(g) + CO2(g)}$
  - (i)
    Write down the rate equation for the above reaction.
  - (ii)
    Which molecule acts as a catalyst in this reaction? Give a reason.
  - (iii)
    Which molecule is an intermediate in this reaction and justify it.
- (b)
  Describe Arrhenius’s equation.
  (8)
Q. 3
(20)
- (a)
  An explosion is usually considered adiabatic, indicating negligible heat transfer, even though it’s rapidly expanding gaseous products are not at the same temperature as the surroundings, and the boundary permits heat transfer. Explain the phenomenon.
  (10)
- (b)
  Draw a working diagram for a reversible heat engine that operates with two isothermal steps and two constant-pressure steps. How many heat reservoirs are needed to operate this engine?
  (10)
Q. 4
(20)
- (a)
  Describe Schrodinger Wave Equation for a particle in a three-dimensional box.
  (10)
- (b)
  Explain photoelectric effect.
  (8)
- (c)
  What is a wave function? Give Born’s interpretation of wave function.
  (2)
Q. 5
(20)
- (b)
  Describe Nernst’s equation.
  (10)
- (b)
  Describe the significance of pH, $\text{pK}_{\text{a}}$ , and $\text{pK}_{\text{b}}$ .
  (6)
- (c)
  What is the relationship between conductance and Kohlrausch’s law?
  (4)
Q. 6
(20)
- (a)
  Describe three methods of mechanical phase separation.
  (10)
- (b)
  Briefly discuss “The Hard-Soft Acid-Base Principle.”
  (10)
Q. 7
(20)
- (a)
  Compare Valence Bond Theory with Molecular Orbital Theory.
  (10)
- (b)
  What is the oxidation state? Differentiate between the oxidation state and valency /covalency of an element with suitable examples.
  (6)
- (c)
  Write the molecular orbital configuration of the followings:
  (4)
  $\ce{O2^+}, \ce{O2}, \ce{O2^-} \text{ and } \ce{O2^{-2}}$
Q. 8
Discuss the following in detail. (5 each)
(20)
- (i)
  Crystal Field Theory
- (ii)
  Hess’s Law
- (iii)
  Electrophoresis Technique
- (iv)
  Freundlich Adsorption Isotherm

Part-II is to be attempted on the separate Answer Book.
Attempt ONLY FOUR questions from PART-II. ALL questions carry EQUAL marks.
All the parts (if any) of each Question must be attempted at one place instead of at different places.
Write Q. No. in the Answer Book in accordance with Q. No. in the Q.Paper.
No Page/Space be left blank between the answers. All the blank pages of Answer Book must be crossed.
Extra attempt of any question or any part of the question will not be considered.
Use of calculator is allowed.