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Q1. Functional groups determine:
A functional group is an atom or group of atoms that gives a carbon compound its characteristic chemical properties. For example, -OH (alcohol) makes compounds like ethanol behave similarly (soluble in water, reaction with sodium). -COOH (carboxylic acid) makes compounds acidic. The functional group determines the chemical nature, not atomic mass, density (which depends on chain length), or shape (which depends on bonding).
Q2. Prefix or suffix in nomenclature indicates:
In IUPAC nomenclature, the prefix or suffix indicates the functional group present. For example, suffix ‘-ol’ indicates alcohol (e.g., ethanol), ‘-al’ indicates aldehyde (e.g., methanal), ‘-one’ indicates ketone (e.g., propanone). Prefix ‘chloro-‘ indicates chlorine atom. Number of atoms is shown by word root (meth-, eth-, prop-). Type of bond is shown by ‘-ane’, ‘-ene’, ‘-yne’. Physical state is not indicated in the name.
Q3. When a suffix is added, the final ‘e’ of alkane name is:
When naming organic compounds, the final letter ‘e’ of the alkane name (e.g., propane, butane) is deleted before adding a suffix that starts with a vowel. For example: Propane + -ol = Propanol (not Propaneol). Ethane + -al = Ethanal (not Ethaneal). Butane + -one = Butanone (not Butaneone). If the suffix starts with a consonant, the ‘e’ is often retained.
Q4. Ethane and propane differ in:
Ethane (C₂H₆) and propane (C₃H₈) are both alkanes with the same functional group (no functional group, just single bonds) and same type of bonds (all single bonds). Carbon valency is 4 in both. They differ by one –CH₂ unit (methylene group). Ethane has 2 carbons, propane has 3 carbons. This is the characteristic of a homologous series.
Q5. Increase in melting and boiling points is due to increase in:
In a homologous series, as the molecular mass increases (more carbon and hydrogen atoms), the intermolecular forces (van der Waals forces) become stronger. This requires more heat energy to overcome, so melting and boiling points increase. Functional group remains the same. Polarity may remain similar. Reactivity generally does not change much. So molecular mass is the key factor.
Q6. Difference between propane and butane is:
Propane (C₃H₈) and butane (C₄H₁₀) are consecutive members of the alkane homologous series. They differ by one –CH₂ unit (methylene group). Propane has 3 carbons, butane has 4 carbons. –C₂H₄ is two –CH₂ units, –CH is not correct (that would change valency), –H₂ is just two hydrogen atoms without carbon.
Q7. Suffix ‘yne’ indicates presence of:
In IUPAC nomenclature, the suffix ‘-yne’ is used for alkynes, which contain a carbon-carbon triple bond (C≡C). For example, ethyne (C₂H₂), propyne (C₃H₄). ‘-ane’ indicates single bonds (alkanes). ‘-ene’ indicates double bonds (alkenes). Hydrogen bonds are intermolecular attractions, not indicated by suffix.
Q8. Suffix ‘ene’ indicates presence of:
The suffix ‘-ene’ is used for alkenes, which contain a carbon-carbon double bond (C=C). For example, ethene (C₂H₄), propene (C₃H₆). ‘-ane’ is for single bonds (alkanes). ‘-yne’ is for triple bonds (alkynes). Ionic bonds are not found in typical organic compounds.
Q9. Difference between CH₄ and C₂H₆ is:
Methane (CH₄) and ethane (C₂H₆) are consecutive members of the alkane series. Methane has 1 carbon, ethane has 2 carbons. They differ by one –CH₂ unit (methylene group). –C₂H₂ would add 2 carbons and 2 hydrogens (but needs 2 hydrogens more for alkane). –CH would add 1 carbon and 1 hydrogen (incomplete valency). –H₂ would add only 2 hydrogens.
Q10. First member of alkene homologous series is:
The alkene homologous series (with double bond) starts with ethene (C₂H₄). There is no “methene” because methane has only one carbon and cannot form a double bond (needs at least 2 carbons). Propene (C₃H₆) is the second member, butene (C₄H₈) is the third. So the first member is ethene.
Q11. An element or group that replaces hydrogen in a carbon compound is called:
In organic chemistry, any atom other than carbon or hydrogen that replaces a hydrogen atom in a hydrocarbon chain is called a heteroatom. Examples: oxygen (in alcohols), nitrogen (in amines), chlorine (in chloroform), etc. Heteroatoms give specific properties to compounds. Radical is a reactive species with unpaired electron. Catalyst speeds up reactions. Isomer is a compound with same formula but different structure.
Q12. ‘One’ is the suffix used for:
In IUPAC nomenclature, the suffix ‘-one’ indicates a ketone functional group (C=O group attached to two carbon atoms). For example, propanone (CH₃COCH₃), butanone. Alcohols use ‘-ol’, aldehydes use ‘-al’, carboxylic acids use ‘-oic acid’. So ‘one’ is for ketones.
Q13. Family of alcohols arranged in increasing carbon atoms forms:
A homologous series is a family of organic compounds having the same functional group (e.g., -OH for alcohols) and similar chemical properties, where each successive member differs by a –CH₂ unit. Methanol (CH₃OH), ethanol (C₂H₅OH), propanol (C₃H₇OH), etc., form the alcohol homologous series. Allotropes are for elements, polymers are large molecules, isomers have same formula but different structure.
Q14. Functional groups replace:
In a hydrocarbon chain, functional groups are introduced by replacing one or more hydrogen atoms. For example, in methane (CH₄), replacing one H with -OH gives methanol (CH₃OH). Replacing one H with -Cl gives chloromethane (CH₃Cl). The carbon skeleton remains the same. Functional groups do not replace oxygen, nitrogen, or carbon atoms in the main chain.
Q15. A homologous series is a series of compounds having:
The defining characteristic of a homologous series is that all members have the same functional group (e.g., -OH for alcohols, -CHO for aldehydes). Physical states vary (methanol is liquid, higher alcohols are solids). Molecular mass increases. Colour is generally not relevant. So same functional group is correct.
Q16. Members of a homologous series show:
In a homologous series, physical properties (melting point, boiling point, density, solubility) show a gradual change (gradation) as molecular mass increases. For example, boiling points of alkanes increase steadily: methane -161°C, ethane -89°C, propane -42°C, butane -0.5°C. There is no sudden change or random behaviour. Chemical properties remain similar.
Q17. General formula of alkanes is:
Alkanes are saturated hydrocarbons with only single bonds. Their general formula is CₙH₂ₙ₊₂, where n = number of carbon atoms. For n=1: CH₄, n=2: C₂H₆, n=3: C₃H₈. CₙH₂ₙ is for cycloalkanes (rings) and alkenes (double bond). CₙH₂ₙ–2 is for alkynes (triple bond) and dienes. CₙHₙ is for benzene-like aromatic compounds.
Q18. Physical properties that change gradually in a homologous series include:
In a homologous series, melting and boiling points increase gradually as molecular mass increases due to stronger van der Waals forces. Functional group remains the same (does not change). Colour generally does not change (most are colourless). Reactivity usually remains similar, not a gradual change. So melting and boiling points show gradation.
Q19. Molecular formula of propene is:
Propene is an alkene (double bond) with 3 carbon atoms. The general formula for alkenes is CₙH₂ₙ. For n=3, C₃H₆. The structure is CH₃–CH=CH₂. C₃H₈ is propane (alkane), C₂H₆ is ethane, C₃H₄ is propyne (alkyne with triple bond). So propene is C₃H₆.
Q20. Successive members of a homologous series differ by:
In a homologous series, each successive member differs from the previous one by one methylene group (–CH₂). This adds one carbon and two hydrogen atoms to the molecular formula. For example, CH₄ (methane) → C₂H₆ (ethane) → C₃H₈ (propane). The difference between any two consecutive members is exactly –CH₂, not –CH₃, –CH, or –C₂H₄.
Q21. Which of the following does not change within a homologous series?
Within a homologous series, all members have the same functional group. For example, all alcohols have -OH, all aldehydes have -CHO. Melting point and boiling point increase with molecular mass (they do change). Molecular mass increases (it changes). So the functional group is the only thing that remains constant.
Q22. Heteroatoms give specific properties to carbon compounds and are therefore called:
A heteroatom (like O, N, S, Cl) or a group containing a heteroatom (like -OH, -CHO, -COOH) that replaces hydrogen in a hydrocarbon and gives specific chemical properties is called a functional group. For example, the -OH group (contains oxygen heteroatom) gives alcohol properties. Homologues are members of a series, radicals are reactive species, isomers have same formula but different structure.
Q23. Carbon atoms can form chains of:
Due to catenation (self-linking property), carbon atoms can form chains of varying lengths — from 1 carbon atom (methane) to thousands of carbon atoms (polymers like polyethylene). Chains are not fixed in length, not limited to two atoms or three atoms. This variation in chain length is what creates the vast diversity of organic compounds.
Q24. Members of alkene homologous series differ by:
In the alkene homologous series (ethene C₂H₄, propene C₃H₆, butene C₄H₈, etc.), each successive member differs by one –CH₂ unit (methylene group). This is true for all homologous series (alkanes, alkenes, alkynes, alcohols, etc.). The difference is always –CH₂, regardless of the functional group.
Q25. Atomic mass of carbon is:
The atomic mass (more accurately, atomic weight) of carbon is 12 u (unified atomic mass units). This is based on the carbon-12 isotope as the standard (exactly 12 u). Carbon-12 has 6 protons and 6 neutrons. 14 u is nitrogen, 6 u would be too low (lithium has 6.94 u), 10 u is boron. So carbon is 12 u.
Q26. Unsaturated carbon chains replace ‘ane’ by:
Unsaturated hydrocarbons are named by replacing the suffix ‘-ane’ (for alkanes) with ‘-ene’ for alkenes (double bond) or ‘-yne’ for alkynes (triple bond). For example: ethane → ethene (C₂H₄) or ethyne (C₂H₂). ‘-one’ is for ketones, ‘-ol’ is for alcohols, ‘-al’ is for aldehydes — these are functional groups, not indicators of unsaturation.
Q27. Naming of carbon compounds is based on:
In IUPAC nomenclature, the first step is to identify the longest continuous carbon chain (the basic carbon chain or parent chain). The name of the compound is derived from this chain (meth-, eth-, prop-, but-). Then the functional group and substituents are added as prefixes or suffixes. Molecular mass and colour are not used. Functional group alone is not enough — the chain length matters.
Q28. Difference between C₂H₆ and C₃H₈ is:
C₂H₆ is ethane, C₃H₈ is propane. They are consecutive alkanes. The difference is one –CH₂ unit (methylene group). C₃H₈ can be written as C₂H₆ + CH₂. –C₂H₄ would add 2 carbons and 4 hydrogens (too many), –CH₃ would add 1 carbon and 3 hydrogens (but that would be CH₃ added to CH₃? Not correct), –H₂ would add only 2 hydrogens. So –CH₂ is correct.
Q29. Methanol belongs to which functional group?
Methanol (CH₃OH) contains the –OH (hydroxyl) group attached to a carbon atom. This is the characteristic functional group of alcohols. Methanol is the simplest alcohol. It is not an acid (though it is weakly acidic), not a ketone (no C=O between two carbons), and not an aldehyde (no -CHO group). So alcohol is correct.
Q30. Ethanol has how many carbon atoms?
Ethanol has the molecular formula C₂H₅OH or C₂H₆O. The prefix ‘eth-‘ indicates 2 carbon atoms. It is the second member of the alcohol homologous series after methanol (CH₃OH, 1 carbon). So ethanol has two carbon atoms. Three carbons is propanol, four is butanol, one is methanol.
Q31. Presence of a functional group makes compounds:
Compounds having the same functional group show similar chemical properties, even if they have different carbon chain lengths. For example, all alcohols (-OH) react with sodium to release hydrogen, all aldehydes (-CHO) undergo oxidation to acids. They are not identical (different chain lengths give different physical properties), but they are chemically similar. They are not inactive — functional groups make them reactive.
Q32. A homologous series shows similarity in:
In a homologous series, all members have the same functional group, so their chemical properties are similar (e.g., all alcohols react with sodium). However, physical properties like melting point, boiling point, density, and solubility show gradation (gradual change) and are not similar. So the similarity is in chemical properties only, not physical properties.
Q33. Molecular formula of butene is:
Butene is an alkene (double bond) with 4 carbon atoms. The general formula for alkenes is CₙH₂ₙ. For n=4, C₄H₈. C₄H₁₀ is butane (alkane), C₄H₆ is butyne (alkyne), C₅H₁₀ is pentene. Butene exists as isomers like 1-butene and 2-butene.
Q34. A compound with three carbon atoms has the base name:
The base names (word roots) for carbon chains are: 1 carbon = meth-, 2 carbons = eth-, 3 carbons = prop-, 4 carbons = but-, 5 carbons = pent-, etc. So a compound with three carbon atoms has the base name propane (if saturated) or propene/propyne (if unsaturated). Methane has 1 carbon, ethane has 2, butane has 4. So propane is correct.
Q35. Solubility in a homologous series depends mainly on:
Solubility of an organic compound depends on the functional group, which determines whether the compound is polar or non-polar. For example, all alcohols (-OH) are soluble in water (due to hydrogen bonding) but solubility decreases as chain length increases. The functional group is the main factor; chain length (molecular mass) affects the degree but not the basic property. Number of atoms alone doesn’t determine solubility.
Q36. Molecular formula of ethene is:
Ethene (also called ethylene) is an alkene with a double bond between two carbon atoms. Its molecular formula is C₂H₄, with structure H₂C=CH₂. CH₄ is methane (alkane), C₂H₂ is ethyne (alkyne), C₂H₆ is ethane (alkane). So C₂H₄ is correct.
Q37. Propane with a ketone group is named:
A ketone functional group is C=O attached to two carbon atoms. Propane (3 carbons) with a ketone group gives the compound CH₃–CO–CH₃ (acetone). Its IUPAC name is propanone. Propanal is an aldehyde (CH₃CH₂CHO), propanol is an alcohol (CH₃CH₂CH₂OH), propanoic acid is a carboxylic acid (CH₃CH₂COOH). So propanone is correct.
Q38. Carbon compounds with same functional group but different chain length are:
Homologues are members of a homologous series — compounds with the same functional group but different carbon chain lengths (differing by –CH₂). For example, methanol (CH₃OH) and ethanol (C₂H₅OH) are homologues. Isomers have the same molecular formula but different structures. Ions are charged species. Allotropes are different forms of the same element.
Q39. The formula of propanol is:
Propanol is an alcohol with 3 carbon atoms. The general formula for alcohols is CₙH₂ₙ₊₁OH. For n=3, C₃H₇OH. This can be written as C₃H₈O. C₂H₅OH is ethanol (2 carbons), CH₃OH is methanol (1 carbon), C₄H₉OH is butanol (4 carbons). So C₃H₇OH is propanol.
Q40. Difference between molecular masses of successive homologues is:
Successive homologues differ by one –CH₂ unit. The atomic mass of carbon is 12 u, and hydrogen is 1 u. So –CH₂ has mass = 12 + (2 × 1) = 14 u. For example, methane (CH₄ = 16 u) and ethane (C₂H₆ = 30 u) differ by 14 u. Ethanol (46 u) and propanol (60 u) also differ by 14 u. So the difference is always 14 u.
Q41. CH₃OH, C₂H₅OH, C₃H₇OH and C₄H₉OH belong to the same:
These are all alcohols with the same functional group (-OH) and differ by –CH₂ units. They form the alcohol homologous series. They are not allotropes (allotropes are for elements like diamond and graphite), not a reaction series (that’s not a standard term), and not isomers (isomers have same molecular formula, but these have different formulas). So homologous series is correct.
Q42. Atomic mass of hydrogen is:
The atomic mass of hydrogen is approximately 1 u (unified atomic mass units). Hydrogen-1 (protium) has 1 proton and 0 neutrons, so its mass is about 1.0078 u, rounded to 1 u. 2 u is deuterium (an isotope, not the standard atomic mass), 4 u is helium, 0.5 u is not possible. So hydrogen is 1 u.
Q43. Homologous series helps in understanding:
A homologous series shows the relationship among organic compounds with the same functional group. It helps predict properties of unknown members based on known members. For example, if you know the boiling point of methane and ethane, you can estimate propane. It does not directly help with the periodic table, nuclear reactions, or atomic structure — those are different areas of chemistry.
Q44. Chemical properties of members of a homologous series are:
All members of a homologous series have the same functional group, so they undergo the same types of chemical reactions under similar conditions. For example, all alkenes undergo addition reactions with bromine, all alcohols react with sodium to release hydrogen. They are not opposite, unrelated, or completely different — they are very similar.
Q45. In nomenclature, ‘propane – e’ gives:
In IUPAC nomenclature, when adding a suffix that starts with a vowel, the final ‘e’ of the alkane name is deleted. ‘Propane’ minus the final ‘e’ gives ‘propan’. Then you add the suffix (like -ol gives propanol, -al gives propanal, -one gives propanone). ‘Propane – e’ itself does not give propene (that would be a different suffix), propone (not a standard name), or propyl (which is an alkyl group). So ‘propan’ is the stem.
Q46. The properties of a carbon compound mainly depend on its:
The chemical properties of a carbon compound are primarily determined by its functional group. For example, all aldehydes (-CHO) give a silver mirror test, all carboxylic acids (-COOH) turn blue litmus red. Chain length affects physical properties (melting point, boiling point) but not chemical properties. Physical state and molecular mass are less important than the functional group.
Q47. Which functional group is present in CH₃OH?
CH₃OH is methanol. It contains the –OH (hydroxyl) group attached to a carbon atom. This is the functional group of alcohols. Aldehydes have –CHO, ketones have C=O between two carbons, acids have –COOH. So the correct functional group is alcohol.
Q48. Butanol contains:
The prefix ‘but-‘ indicates 4 carbon atoms. Butanol is an alcohol with the formula C₄H₉OH (or C₄H₁₀O). So butanol contains four carbon atoms. Two carbons is ethanol, one carbon is methanol, three carbons is propanol. So four is correct.
Q49. Functional groups are attached to the carbon chain by:
In organic chemistry, functional groups replace hydrogen atoms from the carbon chain. The carbon atom that gets the functional group has a free valency (an available bonding site) after removing hydrogen. The functional group attaches to the carbon chain through a covalent bond using this free valency. Metallic and ionic bonds are not involved. Double bonds are a type of bond, not the mechanism of attachment.
Q50. Naming system of carbon compounds helps in:
The IUPAC naming system (nomenclature) gives each organic compound a unique name that reflects its structure — the carbon chain length, the presence and position of functional groups, and any branches. From the name, you can draw the structure. The naming system does not provide density, mass (you need molecular formula for that), or colour (which is not predictable from name alone). So identifying structure is correct.