15 extra multiple-choice questions for Carbon and Its Compounds (10th Standard Science, Samacheer Kalvi), beyond the ones printed in the textbook — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
What is the difference in molecular mass between any two successive members of a homologous series?
- A. 12 amu
- B. 14 amuCorrect
- C. 16 amu
- D. 28 amu
Explanation. Successive members of a homologous series differ by a methylene (-CH2-) group. The atomic mass of carbon is 12 and hydrogen is 1, giving a mass difference of 14 amu.
Q2
Which functional group is present in organic compounds that impart a sweet fruity smell?
- A. -CHO
- B. -COOH
- C. -COORCorrect
- D. -OH
Explanation. Esters contain the functional group -COOR. They are formed by the reaction between a carboxylic acid and an alcohol and are characterized by a sweet fruity odor.
Q3
Which of the following organic compounds is classified as a heterocyclic compound?
- A. Benzene
- B. Cyclobutane
- C. Propane
- D. FuranCorrect
Explanation. Furan contains carbon atoms and an oxygen atom within its ring structure. Compounds containing atoms other than carbon in their cyclic ring are termed heterocyclic.
Q4
An unsaturated hydrocarbon has four carbon atoms and contains one triple bond. What is its molecular formula?
- A. C4H10
- B. C4H8
- C. C4H6Correct
- D. C4H4
Explanation. Alkynes follow the general formula CnH2n-2. For four carbon atoms (n = 4), the number of hydrogen atoms is 2(4) - 2 = 6, yielding C4H6 (butyne).
Q5
What is the percentage purity of ethanol present in absolute alcohol?
- A. 95.5%
- B. 100%Correct
- C. 75%
- D. 50%
Explanation. Absolute alcohol is 100% pure ethanol. It is obtained by refluxing rectified spirit over quicklime followed by distillation.
Q6
What are the primary reactants used in the preparation of soap through saponification?
- A. Mineral acid and alcohol
- B. Oil or fat and aqueous alkaliCorrect
- C. Hydrocarbon and chlorine gas
- D. Carboxylic acid and ester
Explanation. Soap is prepared by heating oil or fat with an alkaline solution like sodium hydroxide. This alkaline hydrolysis of esters present in fats is called saponification.
Q7
In a micelle formed by soap in water, how are the hydrophobic tails oriented?
- A. Pointing outward toward water
- B. Directed inward toward the oil or dirt dropletCorrect
- C. Dissolved completely in water
- D. Bonded covalently to sodium ions
Explanation. Soap molecules have a hydrophilic head and a hydrophobic hydrocarbon tail. In water, the hydrophobic tails cluster inward toward dirt or oil, forming a spherical micelle structure.
Q8
When bromine water is added to an unsaturated hydrocarbon like ethene, what visual change occurs?
- A. Turns dark blue
- B. Decolourizes from reddish-brown to colourlessCorrect
- C. Forms a white precipitate
- D. Evolves effervescence of gas
Explanation. Unsaturated hydrocarbons undergo an addition reaction with bromine water, causing the reddish-brown colour of bromine to disappear. Saturated hydrocarbons do not decolourize bromine water.
Q9
According to IUPAC nomenclature, what is the root word used for a parent carbon chain containing 6 carbon atoms?
- A. Pent-
- B. Hex-Correct
- C. Hept-
- D. Oct-
Explanation. The IUPAC root word specifies the number of carbon atoms in the longest chain. For a chain of 6 carbon atoms, the root word is Hex-.
Q10
Which gas is liberated when ethanoic acid reacts with sodium bicarbonate?
- A. Hydrogen
- B. Oxygen
- C. Carbon dioxideCorrect
- D. Nitrogen dioxide
Explanation. Ethanoic acid reacts with sodium bicarbonate (NaHCO3) to form sodium ethanoate, water, and carbon dioxide gas, which produces brisk effervescence.
Q11
Heating ethanol with concentrated sulphuric acid at high temperature results in the formation of which compound?
- A. Ethane
- B. EtheneCorrect
- C. Ethanoic acid
- D. Diethyl ether
Explanation. Concentrated sulphuric acid acts as a dehydrating agent. Removing a water molecule from ethanol (C2H5OH) converts it into ethene (C2H4).
Q12
Why are synthetic detergents effective cleansing agents even in hard water?
- A. They do not form foam with soft water
- B. Their calcium and magnesium salts are soluble in waterCorrect
- C. They contain no hydrocarbon chains
- D. They are completely insoluble in water
Explanation. Hard water contains calcium and magnesium ions. Detergents form water-soluble calcium and magnesium salts, preventing insoluble scum formation unlike soap.
Q13
The unique ability of carbon atoms to form covalent bonds with other carbon atoms to build long chains is known as what?
- A. Isomerism
- B. Tetravalency
- C. CatenationCorrect
- D. Polymerization
Explanation. Catenation is the property of element atoms to link with themselves via covalent bonds to form straight, branched, or cyclic carbon chains.
Q14
What is the systematic IUPAC name for acetic acid (CH3COOH)?
- A. Methanoic acid
- B. Ethanoic acidCorrect
- C. Propanoic acid
- D. Butanoic acid
Explanation. Acetic acid has two carbon atoms in its chain. Combining the root word Eth-, primary suffix -an-, and secondary suffix -oic acid gives the IUPAC name Ethanoic acid.
Q15
Organic compounds that have the same molecular formula but different structural arrangements are called what?
- A. Allotropes
- B. Isotopes
- C. IsomersCorrect
- D. Homologs
Explanation. Isomers are compounds possessing the identical molecular formula but differing in physical and chemical properties due to distinct structural configurations of atoms.
Frequently asked questions
How many MCQs are there in Carbon and Its Compounds?
This chapter has 15 book-back multiple-choice questions, each with the correct answer and a step-by-step explanation.
Are these 10th Standard Science MCQs free to practise online?
Yes. Every question, answer and explanation here is free, and you can also take them as a timed practice test.
Where can I find the Carbon and Its Compounds book-back answers?
The correct option for each question is highlighted on this page with a worked explanation, plus a quick answer-key summary at the top.
