Class 10 Organic Chemistry Mock Test (ICSE)

Topics in Organic Chemistry

• Unique nature of carbon
• Homologous series and functional groups
• IUPAC nomenclature
• Isomerism
• Alkanes, alkenes and alkynes
• Alcohols and carboxylic acids

Organic Chemistry practice questions with answers

1. Q1Multiple choice·1 mark
   Two successive members of a homologous series differ in their molecular formula by a:

   1. (a)$-CH_3$ group
   2. (b)$-OH$ group
   3. (c)$-CHO$ group
   4. (d)$-CH_2-$ group
   Show answer and step marks

   1. Correct option: (d) $-CH_2-$ group+1

   Answer: (d)
2. Q2Multiple choice·1 mark
   The property of carbon atoms by virtue of which they link to each other to form long chains or rings is called:

   1. (a)Substitution
   2. (b)Polymerisation
   3. (c)Catenation
   4. (d)Isomerism
   Show answer and step marks

   1. Correct option: (c) Catenation+1

   Answer: (c)
3. Q3Multiple choice·1 mark
   The functional group present in carboxylic acids is:

   1. (a)$-OH$
   2. (b)$-COOH$
   3. (c)$>C=O$
   4. (d)$-CHO$
   Show answer and step marks

   1. Correct option: (b) $-COOH$+1

   Answer: (b)
4. Q4Multiple choice·1 mark
   Which of the following catalysts is used during the industrial preparation of alkanes by the catalytic hydrogenation of alkenes?

   1. (a)Nickel
   2. (b)Manganese dioxide
   3. (c)Copper
   4. (d)Iron
   Show answer and step marks

   1. Correct option: (a) Nickel+1

   Answer: (a)
5. Q5Long answer·4 marks
   (a) What is meant by structural isomerism? [1] (b) Draw the structural formulae of the two chain isomers of butane ($\text{C}_4\text{H}_{10}$) and write their respective IUPAC names. [2] (c) Do these isomers have the same empirical formula? Give a reason for your answer. [1]
   Show answer and step marks

   1. (a) Structural isomerism is the phenomenon in which organic compounds have the same molecular formula but different structural arrangements of atoms in their molecules.+1
   2. (b) First isomer: $\text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CH}_3$, IUPAC name: Butane.+1
   3. (b) Second isomer: $\text{CH}_3-\text{CH}(\text{CH}_3)-\text{CH}_3$, IUPAC name: 2-methylpropane.+1
   4. (c) Yes, they have the same empirical formula ($\text{C}_2\text{H}_5$) because they contain carbon and hydrogen atoms in the same simplest ratio of $2:5$.+1

   Answer: (a) Compounds with the same molecular formula but different structural arrangements of atoms. (b) $\text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CH}_3$ (butane) and $\text{CH}_3-\text{CH}(\text{CH}_3)-\text{CH}_3$ (2-methylpropane). (c) Yes, $\text{C}_2\text{H}_5$, since both are $\text{C}_4\text{H}_{10}$ with C : H in the ratio 2 : 5.
6. Q6Long answer·4 marks
   (a) Define the term 'isomerism'. (b) Write the structural formulae and IUPAC names of all possible chain isomers corresponding to the molecular formula $\text{C}_5\text{H}_{12}$.
   Show answer and step marks

   1. Definition: Isomerism is the phenomenon by which two or more compounds possess the same molecular formula but different structural arrangements, resulting in different physical and chemical properties.+1
   2. First isomer: $\text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3$, IUPAC name: Pentane.+1
   3. Second isomer: $\text{CH}_3-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CH}_3$, IUPAC name: 2-methylbutane.+1
   4. Third isomer: $\text{CH}_3-\text{C}(\text{CH}_3)_2-\text{CH}_3$, IUPAC name: 2,2-dimethylpropane.+1

   Answer: (a) Isomerism is the existence of two or more compounds with the same molecular formula but different structures and properties. (b) $\text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3$ (pentane); $\text{CH}_3-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CH}_3$ (2-methylbutane); $\text{CH}_3-\text{C}(\text{CH}_3)_2-\text{CH}_3$ (2,2-dimethylpropane).

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