Chemistry Optional – Other Questions Outside the Present Syllabus (2000–2026)

These 20 questions from UPSC Chemistry Optional papers (2000–2026) fall outside the present syllabus of their paper – mostly from papers set on the older syllabus. We keep them here for completeness.

Each question ends with a code such as [2024/15m/3b] – the year, the marks, the word limit (where UPSC set one) and the question number in the paper.

Paper I

10 questions

1. What is peroxomonosulphuric acid? Give its method of preparation, properties and structure. [2016/10m/8a(ii)]

2. Draw and explain curves showing the variation of first and second ionization energies for the elements from H to Ne. [2014/20m/3c]

3. Discuss any four types of chemical reactions that take place in liquid-ammonia. [2007/20m/8b]

4. Compare the solvent behaviour of liquid ammonia with that of water especially with regard to solvolysis, redox and complexometric reactions. [2006/20m/5a]

5. Define molecular partition function and explain its importance. Show that heat capacity of an ideal gas is $\frac{3}{2}R$. [2005/20m/8a]

6. What are the important reactions of liquid ammonia and liquid sulphur dioxide as non-aqueous solvents. [2004/20m/8a]

7. Define molecular partition function. What is its importance? Calculate the translational contribution to the internal energy of an ideal gas and show that its heat capacity is 3/2 R. [2003/20m/1b]

8. What do you understand by the term “superacid”? Give two chemical properties to justify this nomenclature. [2003/20m/5a]

9. “Ammonium hydroxide is a base in aqueous medium but an acid in liquid ammonia” -Justify this statement using suitable examples. [2003/30m/8b]

10. Complete the following reactions in liquid $S{O}_2$ solvent: (i) $SbC{l}_3+KI\to$ (ii) $C_6{H}_6+S{O}_3\to$ (iii) $KI+SOC{l}_2\to$ (iv) $SbC{l}_3+LiI\to$ [2001/20m/8b]

Paper II

10 questions

1. Write the IUPAC nomenclature of the above compound by assigning the stereochemistry.

[Figure: Zigzag chain CH2=CH–CH(Cl)–CH(OH)–CHO (3-chloro-2-hydroxypent-4-enal skeleton) drawn left to right: terminal vinyl at left; C-3 bears Cl on a hashed (dashed) bond pointing down; C-2 bears OH on a hashed (dashed) bond pointing up; C-1 is the aldehyde C(=O)H at right] [2023/5m/1b(i)]

2. Describe a simple chemical test to distinguish between aniline and benzylamine. [2013/5m/1c(ii)]

3. Amino acids on treatment with ninhydrin give intense blue colour. What is this colouration due to? [2013/15m/6c]

4. Identify the product of the following reaction with mechanism: $R_1{R}_{2}C=C{R}_3{R}_4\underset{\mathrm{\text{(ii)}}WC{l}_6,C_2{H}_{5}OH}{\stackrel{\mathrm{\text{(i)}}{C}_2{H}_{5}AlC{l}_2}{\to }}Product$ [2012/15m/8b]

5. What are the reagents used to distinguish the following pairs? (i) Primary alcohol ($C_2{H}_{5}OH$) and tertiary alcohol (t-Butyl alcohol) (ii) Cyclohexane and 1-Cyclohexene (iii) 1-hexyne and 1-hexene. [2012/15m/8d]

6. Potential Energy (PE) changes during rotation about C(2) – C(3) bond of n-butane. Present the variation semi-quantitatively with rotation of the bond. [2008/20m/1c(i)]

7. Identify A and B in the following reaction. Give reasons for your identification.

[Figure: iodobenzene –$C{l}_2$/$CHC{l}_3$→ A –$N{a}_{2}C{O}_3$→ B] [2006/10m/8c(ii)]

8. 2. 5-dimethyl-1, 1-cyclopentanedicarboxylic acid (I) can be isolated in two optically inactive compounds (A) and (B). Upon heating (A) gives two isomers of 2.5-dimethyj cyclopentanecarboxylic acid (II) whereas (B) yields only one isomer. Draw the structure of isomers of (A) and (B). What is the relationship between the isomers formed by decarboxylation of (A)?

[Figure: (I) cyclopentane C-1 bearing HOOC and COOH, C-2 and C-5 each bearing $C{H}_3$ on a wavy bond –Heat→ (II) cyclopentane C-1 bearing H and COOH, C-2 and C-5 each bearing $C{H}_3$ on a wavy bond; note under the scheme: a boxed wavy line “indicates stereochemistry not specified.”] [2004/20m/1c]

9. Arrange compounds in each of the following sets according to the specified order and give reasons for your choice: Increasing order of stability of three main different conformations of 2-flouroehtanol. [2004/15m/2c]

10. Formaldehyde reacts with ammonia to give A [$C_6{H}_{12}{N}_4$]. A reacts with $HN{O}_3$ to give a well known explosive B[$C_3{H}_6{N}_6{O}_6$]. Predict the structure of B and show how B is formed from A. [2002/0m/7d(i)]

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Last updated: 30 October 2026