Class 10 Science · Original EZT practice
Carbon and its Compounds (Class 10 Chapter 4): original worked practice
Carbon is chemistry's great networker: four bonds per atom, chains, branches and rings, and a naming system that turns structure into words. Chapter 4 runs in three moves - how carbon bonds, how to read and name its compounds, and what those compounds do (burning, oxidising, adding, substituting), ending with ethanol, ethanoic acid and why soap cleans. All examples are original EZT tutor practice, ordered to match the chapter's own section flow. Attempt each before opening the steps.
11 original worked examples, 11 fresh self-check questions and 4 mixed questions, with explained answers. These are not copied textbook exercises, an official chapter index or a full answer key. No affiliation with NCERT is claimed.
Official sources for topic and edition context, checked 18 October 2026:
1. Covalent bonding in carbon
Carbon has 4 electrons in its outermost shell. Gaining or losing 4 is impractical, so carbon shares electrons instead - this sharing is a covalent bond. Methane (CH4) forms four shared pairs; ethene shares two pairs between the carbons (a double bond); ethyne shares three (a triple bond).
2. Saturated and unsaturated; chains, branches and rings
Saturated compounds have only single bonds (alkanes, general formula CnH2n+2). Unsaturated compounds have at least one double bond (alkenes, CnH2n) or triple bond (alkynes, CnH2n-2). Carbon chains can be straight, branched, or closed into rings.
3. Homologous series and nomenclature
A homologous series is a family with the same functional group and the same general formula; successive members differ by a -CH2- unit, i.e. 14 u in molecular mass, and show similar chemical properties. Name the longest chain first, then replace the ending by the functional-group suffix.
4. Chemical properties: the four reaction types
Combustion burns a compound in air to carbon dioxide and water. Oxidation adds oxygen, addition fills a double or triple bond, and substitution swaps one atom for another. Recognising the pattern comes before balancing the equation.
5. Ethanol and ethanoic acid; soaps and detergents
Ethanol is the common alcohol and ethanoic acid is the acid in vinegar. Their reactions lead to esters, hydrogen and carbon dioxide tests. Soap molecules have a water-loving ionic head and an oil-loving carbon tail, so they gather into micelles that lift dirt from cloth.
Choose, solve, check, then try a fresh question.
Before calculating, read the method prompt and name the condition that makes it useful. Write your own attempt. Open the steps only when you need them, and use the check to catch a wrong sign, unit or interpretation. Finish with the fresh question before reading its answer.
Explain why carbon does not form C4+ or C4- ions
Choose the method: Compare the energy and stability cost of gaining, losing or sharing four electrons.
EZT practice question
Why does carbon not form C4+ or C4- ions?
Show the worked solution
- Removing 4 electrons to form C4+ would need too much energy.
- Holding 4 extra electrons as C4- would crowd them into a small shell and create strong repulsion.
- Sharing electrons costs far less energy.
Answer: Carbon forms covalent compounds because gaining or losing four electrons is energetically unfavourable; sharing is much more stable.
Check: Carbon's usual compounds are molecules held together by shared pairs, not simple C4+ or C4- ions.
Watch for this: Do not say carbon has no charge because it is unreactive; the reason is the high cost of a 4+ or 4- ion.
Now try it yourself
Why do covalent compounds generally have low melting and boiling points?
Check your answer
The forces between separate molecules are weak, even though the bonds inside each molecule are strong.
Melting separates molecules; it does not usually break the strong covalent bonds inside them.
Classify hydrocarbons from their formulas
Choose the method: Compare the hydrogen count with CnH2n+2, CnH2n and CnH2n-2.
EZT practice question
Classify as saturated or unsaturated: (i) C3H8 (ii) C4H8 (iii) C5H8.
Show the worked solution
- C3H8 fits CnH2n+2 with n=3, so it is propane.
- C4H8 fits CnH2n with n=4, so it is an alkene.
- C5H8 fits CnH2n-2 with n=5, so it is an alkyne.
Answer: C3H8 is saturated; C4H8 and C5H8 are unsaturated.
Check: The three formulas give three different hydrogen patterns, so they cannot all belong to the same series.
Watch for this: Do not classify by carbon count alone; compare the full formula with the general formula.
Now try it yourself
Write the formula of the alkene with 5 carbon atoms.
Check your answer
C5H10.
An alkene follows CnH2n, so n=5 gives 10 hydrogens.
Test whether C6H14 is saturated
Choose the method: Substitute n=6 into the alkane formula before naming the compound.
EZT practice question
An unknown hydrocarbon has formula C6H14. Is it saturated?
Show the worked solution
- For n=6, CnH2n+2 gives 2(6)+2=14 hydrogens.
- The observed formula C6H14 matches the alkane formula.
- A six-carbon alkane is hexane.
Answer: Yes. C6H14 is saturated, and its name is hexane.
Check: Six carbons and fourteen hydrogens fit exactly CnH2n+2.
Watch for this: Do not call it unsaturated just because the molecule is long; chain length does not decide saturation.
Now try it yourself
Is C2H2 saturated or unsaturated, and what is its common name?
Check your answer
Unsaturated; acetylene (ethyne).
For n=2, CnH2n-2 gives C2H2, the alkyne pattern.
Predict masses in a homologous series
Choose the method: Move one step in the series by adding one CH2 unit, or 14 u.
EZT practice question
Methane CH4 has molecular mass 16 u. Predict the masses of ethane and propane in the alkane series.
Show the worked solution
- Ethane is one CH2 unit after methane: 16+14=30 u.
- Propane is another CH2 unit after ethane: 30+14=44 u.
- Directly, C2H6 is 2(12)+6(1)=30 u and C3H8 is 3(12)+8(1)=44 u.
Answer: Ethane is 30 u and propane is 44 u.
Check: Both predictions match direct atomic-mass calculations.
Watch for this: Do not add 12 u only; the CH2 step adds one carbon and two hydrogens, or 14 u.
Now try it yourself
What is the next member after C4H8 in the alkene series, and by how much does its mass rise?
Check your answer
C5H10, by 14 u.
Successive homologues differ by CH2.
Name compounds from functional groups
Choose the method: Count the longest chain and use -ol, -al or -one for the functional group.
EZT practice question
Name these compounds: (i) CH3CH2CH2OH (ii) CH3CH2CHO (iii) CH3COCH3.
Show the worked solution
- CH3CH2CH2OH has three carbons and an alcohol group, so it is propanol.
- CH3CH2CHO has three carbons and an aldehyde group, so it is propanal.
- CH3COCH3 has three carbons and a ketone group inside the chain, so it is propanone.
Answer: (i) propanol, (ii) propanal, (iii) propanone.
Check: Each name keeps the three-carbon prefix prop- and changes only the suffix.
Watch for this: Do not name only the chain and ignore the functional group.
Now try it yourself
Name CH3CH2CH2CH2OH.
Check your answer
Butanol.
It has four carbons and an -OH alcohol group.
Balance the complete combustion of propane
Choose the method: Balance carbon first, then hydrogen, then oxygen.
EZT practice question
Balance the combustion of propane: C3H8 + O2 -> CO2 + H2O.
Show the worked solution
- Three carbons on the left need 3CO2.
- Eight hydrogens need 4H2O.
- The products contain 6+4=10 oxygen atoms, so use 5O2.
Answer: C3H8 + 5O2 -> 3CO2 + 4H2O.
Check: Left and right both have C3, H8 and O10.
Watch for this: Do not balance oxygen before fixing carbon and hydrogen.
Now try it yourself
Balance: CH4 + O2 -> CO2 + H2O.
Check your answer
CH4 + 2O2 -> CO2 + 2H2O.
One carbon needs one CO2, and four hydrogens need two H2O.
Burn and oxidise ethanol
Choose the method: Use complete combustion for burning and oxygen addition for the permanganate reaction.
EZT practice question
Write the equation for the complete combustion of ethanol, then name the product when ethanol is warmed with alkaline potassium permanganate.
Show the worked solution
- C2H5OH burns completely to 2CO2 and 3H2O.
- That requires 3O2, giving C2H5OH + 3O2 -> 2CO2 + 3H2O.
- Alkaline potassium permanganate oxidises ethanol to ethanoic acid.
Answer: Combustion: C2H5OH + 3O2 -> 2CO2 + 3H2O. Oxidation product: ethanoic acid.
Check: The combustion equation has C2, H6 and O7 on both sides.
Watch for this: Do not call the permanganate reaction combustion; it is controlled oxidation.
Now try it yourself
Which catalyst is used in the hydrogenation of vegetable oils?
Check your answer
Nickel.
Hydrogen adds across the unsaturated bonds in the presence of nickel.
Balance sodium reacting with ethanol
Choose the method: Track sodium atoms and hydrogen molecules carefully.
EZT practice question
Write and balance the reaction of sodium with ethanol.
Show the worked solution
- Ethanol forms sodium ethoxide and hydrogen gas.
- Two ethanol molecules supply the two H atoms needed for one H2 molecule.
- That also balances the two sodium atoms.
Answer: 2Na + 2CH3CH2OH -> 2CH3CH2ONa + H2.
Check: Both sides have Na2, C4, H12 and O2.
Watch for this: Do not write H instead of H2; hydrogen gas is diatomic.
Now try it yourself
Which gas is evolved in this reaction?
Check your answer
Hydrogen.
It gives the familiar pop test with a burning splint.
Use the carbon dioxide test for ethanoic acid
Choose the method: Complete the acid-carbonate reaction, then count atoms on both sides.
EZT practice question
Complete and balance: CH3COOH + NaHCO3 -> ?
Show the worked solution
- A carboxylic acid reacts with sodium hydrogencarbonate to form a salt, water and carbon dioxide.
- The salt is sodium ethanoate, CH3COONa.
- The equation is already balanced with one formula unit of each reactant.
Answer: CH3COOH + NaHCO3 -> CH3COONa + H2O + CO2.
Check: Both sides contain C3, H5, O5 and Na1.
Watch for this: Do not omit water; acid-carbonate reactions give salt, water and carbon dioxide.
Now try it yourself
What observation identifies this reaction?
Check your answer
Brisk effervescence of carbon dioxide.
The gas is released as the acid reacts with the hydrogencarbonate.
Explain how soap lifts oily dirt
Choose the method: Follow the two ends of a soap molecule: ionic head towards water, carbon tail towards oil.
EZT practice question
Why can soap remove an oily patch from cloth, and why does it struggle in hard water?
Show the worked solution
- The long carbon tail mixes with the oil, while the ionic head stays in water.
- Many soap molecules surround the oily dirt as a micelle and lift it off the cloth.
- In hard water, calcium and magnesium salts react with soap to form insoluble scum instead of lather.
Answer: Soap cleans because its two-ended molecules form micelles around oily dirt. Hard water reduces lather because soap is wasted forming scum.
Check: The explanation uses both ends of the soap molecule and the hardness ions.
Watch for this: Do not say soap dissolves oil in water directly; micelles carry the oily dirt into the water.
Now try it yourself
What is esterification, and which acid catalyst does the textbook method use?
Check your answer
An acid plus an alcohol gives an ester and water; concentrated sulphuric acid is used.
Ethanoic acid and ethanol form a sweet-smelling ester under acidic conditions.
Try a mixed set
Choose a method or explanation before opening each answer.
1. What is the general formula of alkanes?
Show answer and reason
CnH2n+2.
Alkanes are saturated hydrocarbons with only single bonds.
2. By what unit do neighbouring homologues differ?
Show answer and reason
CH2, or 14 u.
Each step adds one carbon and two hydrogen atoms.
3. Which reaction adds hydrogen across a double bond in vegetable oil?
Show answer and reason
Hydrogenation, an addition reaction.
A nickel catalyst helps hydrogen add across unsaturated bonds.
4. Which gas confirms ethanoic acid with sodium hydrogencarbonate?
Show answer and reason
Carbon dioxide.
It appears as brisk effervescence.
Try it yourself
Work these on paper before checking any notes. Answers are deliberately not shown here.
- Classify C4H10, C4H8 and C4H6 as alkane, alkene or alkyne.
- Balance the complete combustion of methane.
- Name CH3CH2OH and CH3COOH.
- Why does detergent work better than soap in hard water?
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Questions about this practice page
- What is a functional group?
- An atom or group of atoms, such as -OH, -CHO, >CO or -COOH, attached to a carbon chain that decides the compound's chemical properties, whatever the chain length.
- How do I quickly tell saturated from unsaturated?
- Compare the formula with CnH2n+2. Exactly 2n+2 hydrogens means a saturated alkane; 2n means an alkene with one double bond; 2n-2 means an alkyne with one triple bond.
- Why do alkanes burn with a cleaner flame than vegetable oils?
- Saturated compounds generally burn with a clean blue flame in sufficient air. Unsaturated compounds burn with a yellow, sooty flame because incomplete combustion leaves unburnt carbon particles.
- What is the difference between addition and substitution?
- Addition fills a double or triple bond with new atoms and nothing leaves the molecule. Substitution swaps one atom, often hydrogen, for another, and the replaced atom leaves.
- Are these the NCERT exercise questions for Carbon and its Compounds?
- No. EZT pages are original practice on this chapter - use them to prepare for the textbook exercises, not as a substitute for your book.