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FPSC · CSS 2026

Chemistry, Paper I

100 marks · 3 hours · 6 questions · official PDF, 3 pages
Practice 20 MCQs
This paper Chemistry · all yearsQ. 2 · Explain the difference between physisorption…Q. 3 · Outline selection criteria for stationary…Q. 4 · Given small sample data, compute…Q. 5 · Explain the photoelectric effect and…Q. 6 · (a) Use VSEPR to predict…Q. 7 · Discuss isomerism in coordination complexes…With this paperPart-I MCQs20Official PDF3 pp← 20252026 →
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Part II

Q. 2
  1. (a)Explain the difference between physisorption and chemisorption in terms of energetics and kinetics. Provide typical experimental evidence to distinguish them. [6]
  2. (b)Define and explain the concepts of internal energy (E) and enthalpy (H). Show the mathematical relationship between them. [7]
  3. (c)Discuss the physical meaning of eigenfunctions and eigenvalues, and explain why operators must be Hermitian in quantum mechanics. [7]
(20)
Q. 3
  1. (a)Outline selection criteria for stationary and mobile phases in column chromatography for separating polar organic molecules. [6]
  2. (b)Propose a corrosion prevention strategy for a steel water pipeline system exposed to chloride-rich environments. [7]
  3. (c)Derive the integrated rate equation for a second-order reaction where two reactants of equal concentration react (2A → Products). [7]
(20)
Q. 4
  1. (a)Given small sample data, compute 95% confidence interval for the mean and interpret the result. [6]
  2. (b)Predict and justify which complex will undergo a stronger Jahn-Teller distortion: [Cu(H 2 O) 6 ] 2+ or [Mn(H 2 O) 6 ] 3+ . Support your reasoning with electronic configurations and degeneracy arguments. [7]
  3. (c)Explain how transport numbers are determined experimentally and derive their relationship with ionic mobilities. [7]
(20)
Q. 5
  1. (a)Explain the photoelectric effect and how it supports the particle nature of light. Discuss the role of work function and threshold frequency. [6]
  2. (b)Explain the common ion effect and its application in controlling the solubility of sparingly soluble salts. Use an example to illustrate. [7]
  3. (c)Explain the mechanism of enzyme catalysis, highlighting the role of the active site and the factors that influence enzyme activity. [7]
(20)
Q. 6

(a) Use VSEPR to predict the shape and bond angles of SF4SF_4 and explain the concept of stereochemically active lone pairs.

(b) Using the Van der Waals equation, explain qualitatively how critical constants (Tc, Pc, Vc) relate to a, b parameters.

(c) Explain Debye–Hückel theory and derive the limiting law for the mean ionic activity coefficient. Describe its region of validity.

Checked against official paper
(20)
Q. 7
  1. (a)Discuss isomerism in coordination complexes (geometric, optical, linkage) with three illustrative examples and draw structures. [6]
  2. (b)A buffer is to be made at pH 5.00 using sodium phosphate salts. Which pair would you choose and how would you prepare it? Show calculations. [7]
  3. (c)Explain valence bond theory and hybridization for methane (CH 4 ), and contrast it with an MO description of bonding in the same molecule. [7]
(20)

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About this paper

The 2026 CSS Chemistry paper set by the Federal Public Service Commission. Question wording only; questions marked “Not yet checked” have not been compared with the official paper yet. Open the official paper beside the questions to check any of them.

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