Class 10 Science · Chapter 4

Carbon and its Compounds

442 Class 10 Science questions on Carbon and its Compounds from the NCERT textbook, NCERT Exemplar and CBSE board papers 2017–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 8 of 23

1. Q141 CBSE 2025
   Choose the ​incorrect statement ​about the common ​reaction used ​in ​hydrogenation of ​vegetable oils.

   1. (a)It is an addition reaction.
   2. (b)It takes place in the presence of nickel or palladium catalyst.
   3. (c)The product contains only single bonds between carbon atoms.
   4. (d)It is an addition reaction which occurs in the presence of an acid catalyst.
   Show answer

   (d) It is an addition reaction which occurs in the presence of an acid catalyst.

   Step-by-step solution →
2. Q142 CBSE 2025
   The ​number of ​covalent bond(s) present in ​a ​nitrogen molecule is/are : (Atomic ​number ​of nitrogen ​is 7)

   1. (a)$1$
   2. (b)$3$
   3. (c)$5$
   4. (d)$7$
   Show answer

   (b) $3$

   Step-by-step solution →
3. Q143 CBSE 2025
   The ​products ​obtained ​when sodium ​reacts with ​ethanol are

   1. (a)Sodium ethoxide and hydrogen
   2. (b)Sodium ethoxide and oxygen
   3. (c)Sodium ethanoate and oxygen
   4. (d)Sodium ethanoate and hydrogen
   Show answer

   (a) Sodium ethoxide and hydrogen

   Step-by-step solution →
4. Q144 CBSE 2025
   A ​hydrocarbon ​which is different from the ​other ​three ​is ​:

   1. (a)${\text{C}}_7{\text{H}}_{16}$
   2. (b)${\text{C}}_5{\text{H}}_{10}$
   3. (c)${\text{C}}_2{\text{H}}_6$
   4. (d)${\text{CH}}_4$
   Show answer

   (b) ${\text{C}}_5{\text{H}}_{10}$

   Step-by-step solution →
5. Q145 CBSE 2025
   The ​functional ​group present ​in ​butanone is

   1. (a)$-\text{CHO}$
   2. (b)$-\text{COOH}$
   3. (c)$-\text{OH}$
   4. (d)$>\text{C}=\text{O}$
   Show answer

   (d) $>\text{C}=\text{O}$

   Step-by-step solution →
6. Q146 CBSE 2025
   If ​we ​make ​carbon ​skeleton with four ​carbon atoms, the ​two different possible skeletons ​will be

   1. (a)$\text{C}-\text{C}-\text{C}$ with a fourth $\text{C}$ joined below the third carbon; and $\text{C}-\text{C}-\text{C}-\text{C}$
   2. (b)$\text{C}-\text{C}-\text{C}-\text{C}$; and $\text{C}-\text{C}$ with two further $\text{C}$ atoms joined to the second carbon
   3. (c)$\text{C}-\text{C}-\text{C}-\text{C}$; and $\text{C}-\text{C}$ with a $\text{C}$ joined below the second carbon and a fourth $\text{C}$ below that
   4. (d)$\text{C}-\text{C}-\text{C}-\text{C}$; and $\text{C}-\text{C}$ with one $\text{C}$ joined below each of the two carbons
   Show answer

   (b) $\text{C}-\text{C}-\text{C}-\text{C}$; and $\text{C}-\text{C}$ with two further $\text{C}$ atoms joined to the second carbon

   Step-by-step solution →
7. Q147 CBSE 2025
   Two statements are given ​below ​– one labelled as Assertion ​(A) and the other labelled as Reason (R). Select ​the correct answer ​to this question from the codes (a), (b), (c) and ​(d) given below.

   Assertion (A): Carbon and its compounds are our major sources of fuels.

   Reason (R): Most of the carbon compounds on burning release a large amount of heat and light.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of the Assertion (A).
   3. (c)Assertion (A) is true, but Reason (R) is false.
   4. (d)Assertion (A) is false, but Reason (R) is true.
   Show answer

   (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

   Step-by-step solution →
8. Q148 CBSE 2025
   Two statements are ​given — one ​labelled as Assertion (A) and the ​other ​labelled as Reason (R). Select the correct ​answer to this question from ​the codes ​(a), (b), (c) and (d) as given ​below.

   Assertion (A): Propanal and propanone are structural isomers.

   Reason (R): Propanal and propanone both have the same molecular formula.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
   3. (c)Assertion (A) is true, but Reason (R) is false.
   4. (d)Assertion (A) is false, but Reason (R) is true.
   Show answer

   (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

   Step-by-step solution →
9. Q149 CBSE 2025
   1. (a)Select from the following the members of ​same homologous series :
   2. (b)What ​happens to (i) the ​melting ​point, and (ii) the solubility of compounds as the molecular mass of the compounds ​in ​a homologous ​series increases ?

   Show answer

   Structures (1) and (4) are aldehydes of one homologous series; with rising molecular mass the melting point increases and solubility decreases.

   (a) Structures (1) and (4) belong to the same homologous series: both are aldehydes, propanal ${\text{CH}}_3{\text{CH}}_2\text{CHO}$ and butanal ${\text{CH}}_3{\text{CH}}_2{\text{CH}}_2\text{CHO}$, differing by one $-{\text{CH}}_2-$ unit. (Structure (2) is a ketone and (3) a carboxylic acid.) (b) (i) The melting point increases; (ii) the solubility in water decreases.

   Step-by-step solution →
10. Q150 CBSE 2025
    What ​are micelles ​? ​Draw the structure.
    Show answer

    Micelles are clusters of soap molecules in water, with hydrocarbon tails and oily dirt inside and ionic ends facing the water.

    Micelles are clusters of soap molecules formed in water, in which the hydrophobic hydrocarbon tails are in the interior of the cluster and the ionic (hydrophilic) ends, $-{\text{COO}}^{-}$, lie on its surface facing the water; oily dirt is collected in the centre. Structure: a sphere of soap molecules with the ionic heads on the outside and the hydrocarbon tails pointing inwards around the oily dirt, as in the figure.

    Step-by-step solution →
11. Q151 CBSE 2025
    1. (i)Draw two isomeric structures of ​Butene (${\text{C}}_4{\text{H}}_8$).
    2. (ii)Name the following compounds ​:
    3. (iii)Write the chemical equations ​for ​the following reactions. Mention ​one essential condition each for these reactions to take place. (I) Ethanol undergoes complete oxidation (II) Propene ​undergoes hydrogenation (III) Ethanoic ​acid reacts with ethanol

    Show answer

    But-1-ene and but-2-ene; (I) 1-chloropropane, (II) butanone; ethanol burns in excess air, propene adds hydrogen over nickel, ethanoic acid and ethanol react with conc. sulphuric acid.

    (i) The two isomers are but-1-ene, ${\text{CH}}_2=\text{CH}-{\text{CH}}_2-{\text{CH}}_3$, and but-2-ene, ${\text{CH}}_3-\text{CH}=\text{CH}-{\text{CH}}_3$. (ii) (I) 1-Chloropropane, ${\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_2-\text{Cl}$; (II) Butanone (butan-2-one), ${\text{CH}}_3-{\text{CH}}_2-\text{CO}-{\text{CH}}_3$. (iii) (I) ${\text{C}}_2{\text{H}}_5\text{OH}+3{\text{O}}_2\to 2{\text{CO}}_2+3{\text{H}}_2\text{O}$, the essential condition being that the ethanol is burnt in a sufficient (excess) supply of oxygen or air. (II) ${\text{CH}}_3-\text{CH}={\text{CH}}_2+{\text{H}}_2\to {\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_3$, the essential condition being the presence of a nickel catalyst with warming. (III) ${\text{CH}}_3\text{COOH}+{\text{C}}_2{\text{H}}_5\text{OH}\to {\text{CH}}_3{\text{COOC}}_2{\text{H}}_5+{\text{H}}_2\text{O}$, the essential condition being a few drops of concentrated sulphuric acid with gentle heating.

    Step-by-step solution →
12. Q152 CBSE 2025
    1. (i)A compound ‘X’ having two carbon atoms in its molecule turns blue litmus red ​and $5-8\%$ solution of ‘X’ ​in water is widely used ​as a preservative. Identify the compound ‘X’ and ​write its ​structure.
    2. (ii)Compare its pH ​nature with a mineral acid.
    3. (iii)‘X’ on reacting with alcohols produces sweet smelling compounds, used ​in making perfumes. Name the reaction and write its chemical equation.
    4. (iv)When sodium carbonate is added to ‘X’, a colourless gas is produced which turns lime water milky. Write the ​chemical equation for the reaction giving the name of the salt produced.
    Show answer

    'X' is ethanoic acid, a weaker acid than HCl; it forms esters with alcohols and sodium ethanoate with sodium carbonate.

    (i) X is ethanoic acid (acetic acid), ${\text{CH}}_3\text{COOH}$; its structure is ${\text{H}}_3\text{C}-\text{COOH}$, that is a methyl group joined to a carboxyl group in which the carbon is double bonded to one oxygen and single bonded to an O-H. (ii) Ethanoic acid is a weak acid and ionises only partially, so at the same concentration it gives fewer hydrogen ions and has a higher pH (about $3$) than a mineral acid such as hydrochloric acid (about $1$), which is a strong acid and ionises completely. (iii) The reaction is esterification: ${\text{CH}}_3\text{COOH}+{\text{C}}_2{\text{H}}_5\text{OH}\stackrel{\text{conc. }{\text{H}}_2{\text{SO}}_4}{\to }{\text{CH}}_3{\text{COOC}}_2{\text{H}}_5+{\text{H}}_2\text{O}$. (iv) $2{\text{CH}}_3\text{COOH}+{\text{Na}}_2{\text{CO}}_3⟶2{\text{CH}}_3\text{COONa}+{\text{H}}_2\text{O}+{\text{CO}}_2$; the salt produced is sodium ethanoate (sodium acetate).

    Step-by-step solution →
13. Q153 CBSE 2025
    Write the chemical ​name and the formula of a carbon compound having ​two carbon atoms ​in its molecule and belongs to a family of functional group – OH. ​What happens ​when this compound reacts with the following ? (Give chemical equation and the name of main product formed in each case)

    1. (i)Excess conc. sulphuric acid ​(${\text{H}}_2{\text{SO}}_4$) at 443 K
    2. (ii)​Ethanoic acid in the presence of an acid
    3. (iii)Acidified potassium dichromate
    4. (iv)Sodium metal
    Show answer

    Ethanol, ${\text{C}}_2{\text{H}}_5\text{OH}$, gives ethene with hot conc. sulphuric acid, ethyl ethanoate with ethanoic acid, ethanoic acid with dichromate and sodium ethoxide with sodium.

    The compound is **ethanol**, ${\text{CH}}_3-{\text{CH}}_2-\text{OH}$ (that is, ${\text{C}}_2{\text{H}}_5\text{OH}$; molecular formula ${\text{C}}_2{\text{H}}_6\text{O}$). (i) With excess conc. ${\text{H}}_2{\text{SO}}_4$ at $443$ K it is dehydrated: ${\text{CH}}_3{\text{CH}}_2\text{OH}\underset{443\text{K}}{\overset{{\text{conc. H}}_2{\text{SO}}_4}{\to }}{\text{CH}}_2={\text{CH}}_2+{\text{H}}_2\text{O}$ — main product **ethene**. (ii) With ethanoic acid and an acid catalyst it is esterified: ${\text{CH}}_3\text{COOH}+{\text{C}}_2{\text{H}}_5\text{OH}\stackrel{{\text{conc. H}}_2{\text{SO}}_4}{\to }{\text{CH}}_3{\text{COOC}}_2{\text{H}}_5+{\text{H}}_2\text{O}$ — main product **ethyl ethanoate**, a sweet-smelling ester. (iii) With acidified potassium dichromate it is oxidised: ${\text{CH}}_3{\text{CH}}_2\text{OH}+2[\text{O}]\to {\text{CH}}_3\text{COOH}+{\text{H}}_2\text{O}$ — main product **ethanoic acid**, the orange dichromate turning green. (iv) With sodium metal the hydrogen of the –OH group is replaced: $2{\text{CH}}_3{\text{CH}}_2\text{OH}+2\text{Na}\to 2{\text{CH}}_3{\text{CH}}_2\text{ONa}+{\text{H}}_2\uparrow$ — main product **sodium ethoxide**, with hydrogen gas evolved.

    Step-by-step solution →
14. Q154 CBSE 2025
    A carbon compound 'A' on heating with excess conc. ${\text{H}}_2{\text{SO}}_4$ forms a compound 'B', ​which on addition of one ​mole of ​hydrogen gas in the presence of nickel catalyst forms a compound 'C'. 'C' on ​combustion in air forms 2 moles of carbon dioxide and 3 moles of water. Identify 'A', 'B' and 'C' and write their structures. ​Give chemical equations of the ​reactions involved. Also ​state the role of concentrated sulphuric acid in the formation of ​'B' from 'A'.
    Show answer

    A is ethanol, B ethene, C ethane; conc. sulphuric acid acts as a dehydrating agent, removing water from ethanol.

    'A' is ethanol, ${\text{CH}}_3-{\text{CH}}_2-\text{OH}$; 'B' is ethene, ${\text{CH}}_2={\text{CH}}_2$; and 'C' is ethane, ${\text{CH}}_3-{\text{CH}}_3$. Structures: ethanol has two carbons joined by a single bond with an $-\text{OH}$ on the end carbon and hydrogen filling every other valency; ethene has the two carbons joined by a double bond with two hydrogens on each; ethane has them joined by a single bond with three hydrogens on each. Equations: ${\text{CH}}_3{\text{CH}}_2\text{OH}\underset{443\text{K}}{\overset{\text{excess conc. }{\text{H}}_2{\text{SO}}_4}{\to }}{\text{CH}}_2={\text{CH}}_2+{\text{H}}_2\text{O}$; ${\text{CH}}_2={\text{CH}}_2+{\text{H}}_2\stackrel{\text{Ni},\Delta }{\to }{\text{CH}}_3-{\text{CH}}_3$; $2{\text{C}}_2{\text{H}}_6+7{\text{O}}_2⟶4{\text{CO}}_2+6{\text{H}}_2\text{O}$. Role of concentrated sulphuric acid: it acts as a dehydrating agent, removing a molecule of water from ethanol to give the unsaturated compound ethene.

    Step-by-step solution →
15. Q155 CBSE 2025
    1. (a)What ​is meant by the term homologous series of carbon compounds ? Write molecular formula of any two consecutive ​members of homologous series of ketones.
    2. (b)Write chemical equation of the reactions ​of ethanoic acid with (i) Sodium hydroxide ​and (ii) Ethanol ​(in the presence of ​an acid); giving the name of the products in each case. (c) Draw the ​structure of the molecule of benzene.
    Show answer

    A homologous series has one functional group and members differing by $-{\text{CH}}_2-$; ethanoic acid gives sodium ethanoate with NaOH and ethyl ethanoate with ethanol.

    (a) A homologous series is a family of carbon compounds having the **same** functional group, in which each member differs from the next by a $-{\text{CH}}_2-$ unit (a mass difference of $14$ u). All members fit one general formula, they have similar chemical properties, and their physical properties change gradually along the series. Two consecutive members of the ketone series (${\text{C}}_n{\text{H}}_{2n}\text{O}$): propanone ${\text{C}}_3{\text{H}}_6\text{O}$ and butanone ${\text{C}}_4{\text{H}}_8\text{O}$. (b) (i) ${\text{CH}}_3\text{COOH}+\text{NaOH}\to {\text{CH}}_3\text{COONa}+{\text{H}}_2\text{O}$; the products are sodium ethanoate (sodium acetate) and water. (ii) ${\text{CH}}_3\text{COOH}+{\text{C}}_2{\text{H}}_5\text{OH}\stackrel{{\text{conc. H}}_2{\text{SO}}_4}{\to }{\text{CH}}_3{\text{COOC}}_2{\text{H}}_5+{\text{H}}_2\text{O}$; the products are ethyl ethanoate (an ester) and water. (c) Benzene, ${\text{C}}_6{\text{H}}_6$, is a ring of six carbon atoms with alternate single and double bonds and one hydrogen atom on each carbon, as drawn in the figure.

    Step-by-step solution →
16. Q156 CBSE 2025
    Name ​an alcohol and a carboxylic acid having two carbon atoms in their ​structures. Draw their structures and state how ​this alcohol can be converted into a ​carboxylic ​acid. What happens when these two compounds react in ​the ​presence of an acid ? Write chemical equations for the reactions involved in the two cases mentioned above.
    Show answer

    Ethanol, ${\text{CH}}_3{\text{CH}}_2\text{OH}$, is oxidised to ethanoic acid, ${\text{CH}}_3\text{COOH}$; the two react with an acid catalyst to form the ester ethyl ethanoate and water.

    The alcohol is ethanol, ${\text{CH}}_3-{\text{CH}}_2-\text{OH}$, and the carboxylic acid is ethanoic acid, ${\text{CH}}_3-\text{COOH}$, in which the second carbon is doubly bonded to one oxygen and singly bonded to an $-\text{OH}$ group. Ethanol is converted into ethanoic acid by oxidation, on warming with alkaline potassium permanganate (or acidified potassium dichromate): ${\text{CH}}_3{\text{CH}}_2\text{OH}+2[\text{O}]⟶{\text{CH}}_3\text{COOH}+{\text{H}}_2\text{O}$. When the two compounds are warmed together in the presence of a little concentrated sulphuric acid they undergo esterification, forming ethyl ethanoate, an ester with a sweet fruity smell, and water: ${\text{CH}}_3\text{COOH}+{\text{C}}_2{\text{H}}_5\text{OH}⟶{\text{CH}}_3{\text{COOC}}_2{\text{H}}_5+{\text{H}}_2\text{O}$.

    Step-by-step solution →
17. Q157 CBSE 2025
    1. (i)Give reason ​why ​carbon can neither form ${\text{C}}^{4+}$ cations nor ${\text{C}}^{4-}$ anions but forms covalent compounds.
    2. (ii)What is a homologous series ​of carbon compounds ? Write the molecular formula ​of any two consecutive members of a homologous series of aldehydes.
    3. (iii)Write the number of ​(1) ​single covalent bonds ​and (2) double ​covalent bonds in a molecule of benzene.
    Show answer

    Carbon shares electrons; methanal ${\text{CH}}_2\text{O}$ and ethanal ${\text{C}}_2{\text{H}}_4\text{O}$ are consecutive aldehydes; benzene has 9 single and 3 double bonds.

    (i) Carbon has the configuration $2,4$, so it has four valence electrons. Losing four electrons to give ${\text{C}}^{4+}$ would need a very large amount of energy, and gaining four to give ${\text{C}}^{4-}$ would leave ten electrons to be held by only six protons, which is not stable. Carbon therefore completes its octet by sharing its four valence electrons, forming four covalent bonds. (ii) A homologous series is a series of carbon compounds with the same functional group in which successive members differ by one ${\text{CH}}_2$ unit, share one general formula and similar chemical properties, and show a gradation in physical properties. Two consecutive aldehydes are methanal ${\text{CH}}_2\text{O}$ and ethanal ${\text{C}}_2{\text{H}}_4\text{O}$. (iii) Benzene has $9$ single covalent bonds, namely six C to H and three C to C, and $3$ double covalent bonds.

    Step-by-step solution →
18. Q158 CBSE 2025
    1. (i)What are structural isomers ? Draw structural isomers of butane (${\text{C}}_4{\text{H}}_{10}$). Give reason ​why propane has no structural ​isomers ?
    2. (ii)What happens when butane is burnt in air ? ​Write ​chemical ​equation for the reaction. Differentiate between the flames obtained when butane and butyne both ​are burnt in air in ​the ​similar conditions.
    Show answer

    Butane has two structural isomers, n-butane and iso-butane; propane has none; butane burns with a blue flame, butyne with a sooty yellow one.

    (i) Structural isomers are compounds that have the same molecular formula but different structures. Butane, ${\text{C}}_4{\text{H}}_{10}$, has two: n-butane, ${\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_2-{\text{CH}}_3$, a straight chain, and iso-butane (2-methylpropane), ${\text{CH}}_3-\text{CH}({\text{CH}}_3)-{\text{CH}}_3$, a branched chain; their full structures are drawn in the figure. Propane, ${\text{C}}_3{\text{H}}_8$, has no structural isomers because its three carbon atoms can be joined in only one way, as a chain of three; a branched chain needs at least four carbon atoms. (ii) Butane burns in air to form carbon dioxide and water, giving out a large amount of heat and light: $2{\text{C}}_4{\text{H}}_{10}+13{\text{O}}_2\to 8{\text{CO}}_2+10{\text{H}}_2\text{O}$. Butane, a saturated hydrocarbon, burns with a clean blue flame, while butyne, an unsaturated hydrocarbon, burns with a yellow, sooty flame giving black smoke.

    Step-by-step solution →
19. Q159 CBSE 2025
    (a) Define the term ​“Functional ​group ​of a carbon compound”. Write ​the formula of functional group present in

    1. (i)propanol and
    2. (ii)propanone. (b) Name the process of conversion of (i) ethanol to ​ethene and (ii) ethanol to ethanoic ​acid. Write the reaction equation stating the conditions required for each of the reactions ​to ​occur.
    Show answer

    Functional group gives characteristic properties; propanol has $-\text{OH}$, propanone $>\text{C}=\text{O}$; ethanol to ethene is dehydration, ethanol to ethanoic acid is oxidation.

    (a) A functional group is an atom or a group of atoms, such as $-\text{OH}$, $-\text{CHO}$ or $-\text{COOH}$, that replaces hydrogen in a hydrocarbon chain and gives the compound its characteristic chemical properties, whatever the length and nature of the carbon chain. (i) Propanol, ${\text{CH}}_3{\text{CH}}_2{\text{CH}}_2\text{OH}$: the alcohol group, $-\text{OH}$. (ii) Propanone, ${\text{CH}}_3{\text{COCH}}_3$: the ketone group, $>\text{C}=\text{O}$ (written $-\text{CO}-$ in a condensed formula). (b) (i) Ethanol to ethene is dehydration: when ethanol is heated at 443 K with excess concentrated sulphuric acid, the acid removes a molecule of water from each molecule of ethanol. ${\text{CH}}_3{\text{CH}}_2\text{OH}\underset{443\text{K}}{\overset{{\text{hot conc. H}}_2{\text{SO}}_4}{\to }}{\text{CH}}_2={\text{CH}}_2+{\text{H}}_2\text{O}$ (ii) Ethanol to ethanoic acid is oxidation: ethanol is heated with alkaline potassium permanganate (or acidified potassium dichromate), which adds oxygen to it. ${\text{CH}}_3{\text{CH}}_2\text{OH}+2[\text{O}]\underset{\text{heat}}{\overset{{\text{alkaline KMnO}}_4}{\to }}{\text{CH}}_3\text{COOH}+{\text{H}}_2\text{O}$

    Step-by-step solution →
20. Q160 CBSE 2025
    1. (i)A carbon compound X is a good solvent. On reaction with sodium, X forms two ​products ​Y and Z. Z is used ​to convert vegetable oil ​into vegetable ghee. ​Identify and name X, Y and Z. Also write the equation of reaction of X with sodium to justify your answer.
    2. (ii)Write ​chemical equation to show what happens when ethanol ​: (I) burns in oxygen/air. (II) is heated at 443 K in excess conc. ${\text{H}}_2{\text{SO}}_4$. (III) reacts with acidified potassium ​dichromate.
    Show answer

    X is ethanol, Y sodium ethoxide, Z hydrogen; ethanol burns to carbon dioxide and water, dehydrates to ethene, and is oxidised to ethanoic acid.

    (i) $X$ is ethanol, ${\text{C}}_2{\text{H}}_5\text{OH}$; $Y$ is sodium ethoxide, ${\text{C}}_2{\text{H}}_5\text{ONa}$; and $Z$ is hydrogen gas, ${\text{H}}_2$, which hardens vegetable oil into vegetable ghee by hydrogenation over a nickel catalyst. The justifying equation is $2{\text{C}}_2{\text{H}}_5\text{OH}+2\text{Na}\to 2{\text{C}}_2{\text{H}}_5\text{ONa}+{\text{H}}_2\uparrow$. (ii) (I) ${\text{C}}_2{\text{H}}_5\text{OH}+3{\text{O}}_2\to 2{\text{CO}}_2+3{\text{H}}_2\text{O}+\text{heat and light}$. (II) ${\text{C}}_2{\text{H}}_5\text{OH}\to {\text{CH}}_2={\text{CH}}_2+{\text{H}}_2\text{O}$, with excess concentrated ${\text{H}}_2{\text{SO}}_4$ at $443$ K acting as the dehydrating agent. (III) ${\text{CH}}_3{\text{CH}}_2\text{OH}+2[\text{O}]\to {\text{CH}}_3\text{COOH}+{\text{H}}_2\text{O}$ with warm acidified ${\text{K}}_2{\text{Cr}}_2{\text{O}}_7$, so ethanol is oxidised to ethanoic acid.

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