Carbon exists in the atmosphere in the form of
carbon monoxide only
carbon monoxide in traces and carbon dioxide
carbon dioxide only
coal
Which of the following statements are usually correct for carbon compounds?
(i) are good conductors of electricity
(ii) are poor conductors of electricity
(iii) have strong forces of attraction between their molecules
(iv) do not have strong forces of attraction between their molecules
(i) and (iii)
(ii) and (iii)
(i) and (iv)
(ii) and (iv)
A molecule of ammonia (NH₃) has
only single bonds
only double bonds
only triple bonds
two double bonds and one single bond
Buckminsterfullerene is an allotropic form of
phosphorus
sulphur
carbon
tin
Which of the following are correct structural isomers of butane?
(i) and (iii)
(ii) and (iv)
(i) and (ii)
(iii) and (iv)
In the reaction CH₃–CH₂–OH → CH₃–COOH (Alkaline KMnO₄ + Heat), alkaline KMnO₄ acts as
reducing agent
oxidising agent
catalyst
dehydrating agent
Oils treated with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of
Addition reaction
Substitution reaction
Displacement reaction
Oxidation reaction
In which of the following compounds, —OH is the functional group?
Butanone
Butanol
Butanoic acid
Butanal
The soap molecule has
a hydrophilic head and a hydrophobic tail
a hydrophobic head and a hydrophilic tail
a hydrophobic head and a hydrophobic tail
a hydrophilic head and a hydrophilic tail
Which of the following is the correct representation of electron dot structure of nitrogen?
N : N
:N : N:
N : : N
:N ≡ N:
Structural formula of ethyne is
H–C≡C–H
H₃–C≡C–H
C=C
H–C=C–H
Identify the unsaturated compounds from the following:
(i) Propane
(ii) Propene
(iii) Propyne
(iv) Chloropropane
(i) and (ii)
(ii) and (iv)
(iii) and (iv)
(ii) and (iii)
Chlorine reacts with saturated hydrocarbons at room temperature in the
absence of sunlight
presence of sunlight
presence of water
presence of hydrochloric acid
In the soap micelles
the ionic end of soap is on the surface of the cluster, carbon chain in interior
ionic end is in interior, carbon chain out
both ionic end and carbon chain are in the interior
both ionic end and carbon chain are on the exterior
Pentas has molecular formula C₅H₁₂. It has
5 covalent bonds
12 covalent bonds
16 covalent bonds
17 covalent bonds
Structural formula of benzene is
structure a
structure b
structure c
structure d
Ethanol reacts with sodium and forms two products. These are
sodium ethanoate and hydrogen
sodium ethanoate and oxygen
sodium ethoxide and hydrogen
sodium ethoxide and oxygen
The correct structural formula of butanoic acid is
structure a
structure b
structure c
structure d
Vinegar is a solution of
50%–60% acetic acid in alcohol
5%–8% acetic acid in alcohol
5%–8% acetic acid in water
50%–60% acetic acid in water
Mineral acids are stronger acids than carboxylic acids because
(i) mineral acids are completely ionised
(ii) carboxylic acids are completely ionised
(iii) mineral acids are partially ionised
(iv) carboxylic acids are partially ionised
(i) and (iv)
(ii) and (iii)
(i) and (ii)
(iii) and (iv)
Carbon forms four covalent bonds by sharing electrons with four univalent atoms. After these four bonds, carbon attains the electronic configuration of
helium
neon
argon
krypton
The correct electron dot structure of a water molecule is
H·Ö·H
H:Ö:H
H:Ö:H
H·O·H
Which of the following is not a straight-chain hydrocarbon?
structure a
structure b
structure c
structure d
Which among the following are unsaturated hydrocarbons?
(i) H₃C—CH₂—CH₂—CH₃
(ii) H₃C—C≡C—CH₃
(iii) H₃C—CH—CH₃
(iv) H₃C—C≡CH
(i) and (ii)
(ii) and (iii)
(ii) and (iv)
(iii) and (iv)
Which of the following does not belong to the same homologous series?
CH₄
C₂H₆
C₃H₈
C₄H₈
The name of the compound CH₃—CH₂—CHO is
Propanal
Propanone
Ethanol
Ethanal
The heteroatoms present in CH₃—CH₂—O—CH₂—CH₂Cl are
(i) oxygen
(ii) carbon
(iii) hydrogen
(iv) chlorine
(i) and (ii)
(ii) and (iii)
(iii) and (iv)
(i) and (iv)
Which of the following represents saponification reaction?
reaction a
reaction b
reaction c
reaction d
The first member of alkyne homologous series is
ethyne
ethene
propyne
methane
Draw the electron dot structure of ethyne and also draw its structural formula.
Electron dot structure of ethyne (\(C_2H_2\)):
H : C ≡ C : H
Structural formula:
H — C ≡ C — H
Write the names of the given compounds.
(a) Pentanoic acid
(b) Butyne
(c) Heptanal
(d) Pentanol
Identify and name the functional groups present in the following compounds.
(a) —OH → Hydroxyl/Alcohol
(b) —C(=O)OH → Carboxylic acid
(c) —C(=O)— → Ketone
(d) —C=C— → Alkene
A compound X is formed by the reaction of a carboxylic acid and an alcohol in the presence of a few drops of \(H_2SO_4\). The alcohol on oxidation gives the same carboxylic acid used in this reaction. Give the names and structures of the carboxylic acid, the alcohol, and the compound X. Also write the reaction.
Carboxylic acid: Ethanoic acid (\(CH_3COOH\))
Alcohol: Ethanol (\(C_2H_5OH\))
Compound X: Ethyl ethanoate (\(CH_3COOC_2H_5\))
Reaction:
\(CH_3COOH + C_2H_5OH \xrightarrow{H_2SO_4} CH_3COOC_2H_5 + H_2O\)
Why are detergents better cleansing agents than soaps?
Detergents work as cleansing agents in both soft and hard water. Their charged ends do not form insoluble precipitates with calcium and magnesium ions present in hard water.
Name the functional groups present in the following compounds.
(a) Ketone
(b) Carboxylic acid
(c) Aldehyde
(d) Alcohol
How is ethene prepared from ethanol? Give the reaction involved.
Ethene is prepared by the dehydration of ethanol using hot concentrated sulphuric acid at 443 K.
Reaction:
\(CH_3CH_2OH \xrightarrow[443K]{conc.\ H_2SO_4} CH_2 = CH_2 + H_2O\)
Intake of small quantity of methanol can be lethal. Comment.
Methanol is oxidised to methanal in the liver. Methanal reacts rapidly with cell components, causing the protoplasm to coagulate. It affects the optic nerve and may cause blindness or death.
A gas is evolved when ethanol reacts with sodium. Name the gas evolved and write the balanced chemical equation.
Gas evolved: Hydrogen
Equation:
\(2CH_3CH_2OH + 2Na → 2CH_3CH_2O^-Na^+ + H_2\)
Ethene is formed when ethanol is heated at 443 K with excess of concentrated sulphuric acid. What is the role of sulphuric acid in this reaction? Write the balanced equation.
Role: Sulphuric acid acts as a dehydrating agent.
Equation:
\(CH_3CH_2OH \xrightarrow[443K]{conc.\ H_2SO_4} CH_2 = CH_2 + H_2O\)
Write an example of a compound formed with chlorine (Group 17) and one formed with oxygen (Group 16).
(a) With chlorine: Carbon tetrachloride (\(CCl_4\))
(b) With oxygen: Carbon dioxide (\(CO_2\))
In electron dot structure, valence electrons are represented by dots or crosses.
(a) The atomic number of chlorine is 17. Write its electronic configuration.
(b) Draw the electron dot structure of a chlorine molecule.
(a) Electronic configuration: 2, 8, 7
(b) Electron dot structure: :Cl⋯Cl:
Compare the ability of catenation of carbon with silicon. Give reasons.
Carbon shows greater catenation ability than silicon because carbon–carbon bonds are stronger due to the smaller atomic size of carbon. Silicon atoms are larger, making Si–Si bonds weaker.
Unsaturated hydrocarbons contain multiple bonds and show addition reactions. Give the test to distinguish ethane from ethene.
Burning test: Unsaturated hydrocarbons (like ethene) burn with a yellow smoky flame, while saturated hydrocarbons (like ethane) burn with a clear blue flame.
Match the reactions in Column (A) with the names in Column (B).
(a) → (iv)
(b) → (i)
(c) → (ii)
(d) → (iii)
Write the structural formulae of all the isomers of hexane.
(a) n-Hexane
(b) 2-Methylpentane
(c) 3-Methylpentane
(d) 2,3-Dimethylbutane
(e) 2,2-Dimethylbutane
What is the role of the metal or reagents written on the arrows in the chemical reactions?
(a) Ni acts as a catalyst.
(b) Concentrated \(H_2SO_4\) acts as a catalyst.
(c) Alkaline \(KMnO_4\) acts as an oxidising agent.
A salt X is formed and a gas is evolved when ethanoic acid reacts with sodium hydrogencarbonate. Name the salt X and the gas evolved. Describe an activity and draw the diagram of the apparatus to prove that the evolved gas is the one which you have named. Also, write the chemical equation of the reaction involved.
Salt formed: Sodium ethanoate (\(CH_3COONa\))
Gas evolved: Carbon dioxide (\(CO_2\))
Activity:
Take a test tube and add a small amount of sodium hydrogencarbonate.
Add ethanoic acid (acetic acid) to it through a thistle funnel.
A brisk effervescence appears due to evolution of \(CO_2\).
Pass the gas produced through lime water using a delivery tube.
The lime water turns milky, confirming the presence of \(CO_2\).
Chemical equation:
\[ CH_3COOH + NaHCO_3 \rightarrow CH_3COONa + H_2O + CO_2 \]
(a) What are hydrocarbons? Give examples.
(b) Give the structural differences between saturated and unsaturated hydrocarbons with two examples each.
(c) What is a functional group? Give examples of four different functional groups.
(a) Hydrocarbons: Compounds made up of carbon and hydrogen atoms only. Examples: methane (\(CH_4\)), ethane (\(C_2H_6\)).
(b) Structural differences:
Saturated hydrocarbons: Contain only single bonds between carbon atoms.
Examples:
Methane: \(CH_4\)
Ethane: \(CH_3-CH_3\)
Unsaturated hydrocarbons: Contain at least one double or triple bond.
Examples:
Ethene: \(CH_2=CH_2\)
Ethyne: \(CH\equiv CH\)
(c) Functional group: An atom or group of atoms that gives characteristic chemical properties to a compound.
Examples:
Hydroxyl group (−OH)
Carboxyl group (−COOH)
Aldehyde group (−CHO)
Ketone group (\(C=O\))
Name the reaction which is commonly used in the conversion of vegetable oils to fats. Explain the reaction involved in detail.
Reaction name: Hydrogenation reaction
Explanation:
Vegetable oils contain unsaturated hydrocarbons (double bonds). When hydrogen gas is passed through the oil in the presence of a nickel catalyst and moderate heat, the double bonds are converted into single bonds. This forms saturated fats, which are solid at room temperature.
Chemical representation:
\[ R−C = C−R + H_2 \xrightarrow{Ni} R−CH−CH−R \]
This process converts liquid oils into semi-solid or solid fats such as vanaspati ghee.
(a) Write the formula and draw the electron dot structure of carbon tetrachloride.
(b) What is saponification? Write the reaction involved in this process.
(a) Carbon tetrachloride:
Formula: \(CCl_4\)
Electron dot structure:
C is surrounded by four Cl atoms with shared electron pairs as single covalent bonds (represented diagrammatically).
(b) Saponification:
Saponification is the process in which an ester reacts with a base to form a salt of a carboxylic acid (soap) and alcohol.
Reaction:
\[ CH_3COOC_2H_5 + NaOH \rightarrow CH_3COONa + C_2H_5OH \]
Esters are sweet-smelling substances and are used in making perfumes. Suggest some activity and the reaction involved for the preparation of an ester with a well-labeled diagram.
Activity to prepare an ester:
Take 1 mL ethanol and 1 mL glacial acetic acid in a test tube.
Add a few drops of concentrated sulphuric acid.
Warm the mixture in a water bath for 10–15 minutes.
Pour into a beaker containing water and smell the sweet fruity ester formed.
Reaction:
\[ CH_3COOH + C_2H_5OH \xrightarrow{Conc.\ H_2SO_4} CH_3COOC_2H_5 + H_2O \]
Diagram: (The setup includes a test tube containing reactants, placed in a water bath and heated gently.)
A compound C (molecular formula \(C_2H_4O_2\)) reacts with Na-metal to form a compound R and evolves a gas which burns with a pop sound. Compound C on treatment with an alcohol \(A\) in the presence of an acid forms a sweet-smelling compound S (molecular formula \(C_3H_6O_2\)). On addition of NaOH to C, it also gives R and water. S on treatment with NaOH solution gives back R and A. Identify C, R, A, S and write the reactions involved.
Identification:
C = Ethanoic acid (\(CH_3COOH\))
R = Sodium ethanoate (\(CH_3COONa\))
A = Methanol (\(CH_3OH\))
S = Methyl ethanoate (\(CH_3COOCH_3\))
Reactions involved:
1. Reaction of C with Na:
\[ 2CH_3COOH + 2Na \rightarrow 2CH_3COONa + H_2 \]
2. Esterification reaction:
\[ CH_3COOH + CH_3OH \xrightarrow{Conc.\ H_2SO_4} CH_3COOCH_3 + H_2O \]
3. Reaction of C with NaOH:
\[ CH_3COOH + NaOH \rightarrow CH_3COONa + H_2O \]
4. Saponification of ester S:
\[ CH_3COOCH_3 + NaOH \rightarrow CH_3COONa + CH_3OH \]
Look at Figure 4.1 and answer the following questions:
(a) What change would you observe in the calcium hydroxide solution taken in tube B?
(b) Write the reaction involved in test tubes A and B respectively.
(c) If ethanol is given instead of ethanoic acid, would you expect the same change?
(d) How can a solution of lime water be prepared in the laboratory?
(a) The calcium hydroxide solution (lime water) in tube B will turn milky.
(b) Reactions involved:
In test tube A:
\[ 2CH_3COOH + Na_2CO_3 \rightarrow 2CH_3COONa + H_2O + CO_2 \]
In test tube B:
\[ Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O \]
With excess CO₂, milkiness disappears:
\[ CaCO_3 + H_2O + CO_2 \rightarrow Ca(HCO_3)_2 \]
(c) No. Ethanol does not react with sodium carbonate, so no CO₂ is produced and no milky appearance is observed.
(d) Lime water is prepared by dissolving calcium oxide in water and decanting the clear supernatant liquid.
How would you bring about the following conversions? Name the process and write the reaction involved.
(a) Ethanol to ethene
(b) Propanol to propanoic acid
(a) Ethanol to ethene — Dehydration
Ethanol is heated with concentrated sulphuric acid at 443 K to form ethene.
\[ CH_3CH_2OH \xrightarrow[443K]{Hot\ conc.\ H_2SO_4} CH_2 = CH_2 + H_2O \]
(b) Propanol to propanoic acid — Oxidation
Propanol is oxidised using alkaline potassium permanganate (KMnO₄).
\[ CH_3CH_2CH_2OH \xrightarrow{Alk.\ KMnO_4,\ Heat} CH_3CH_2COOH \]
Draw the possible isomers of the compound with molecular formula \(C_3H_6O\) and also give their electron dot structures.
The possible isomers of \(C_3H_6O\) are:
(1) Propanone
Structure: \(CH_3−CO−CH_3\)
Electron dot structure includes a carbonyl group with each carbon bonded appropriately (diagrammatic representation).
(2) Propanal
Structure: \(CH_3−CH_2−CHO\)
Electron dot structure shows the aldehyde group with proper valence electrons around O and C.
Explain the given reactions with examples:
(a) Hydrogenation reaction
(b) Oxidation reaction
(c) Substitution reaction
(d) Saponification reaction
(e) Combustion reaction
(a) Hydrogenation reaction:
Unsaturated hydrocarbons add hydrogen in the presence of nickel catalyst.
\[ RC = CR + H_2 \xrightarrow{Ni} RCH−CHR \]
(b) Oxidation reaction:
Ethanol is oxidised to ethanoic acid by alkaline KMnO₄.
\[ CH_3CH_2OH \xrightarrow{Alk.\ KMnO_4,\ Heat} CH_3COOH \]
(c) Substitution reaction:
Chlorine replaces hydrogen in methane in presence of sunlight.
\[ CH_4 + Cl_2 \xrightarrow{h u} CH_3Cl + HCl \]
(d) Saponification reaction:
Esters react with alkali to form soap and alcohol.
\[ CH_3COOC_2H_5 + NaOH \rightarrow CH_3COONa + C_2H_5OH \]
(e) Combustion reaction:
Carbon compounds burn in oxygen to produce \(CO_2\), \(H_2O\), heat and light.
\[ CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O + \text{Heat} \]
An organic compound A on heating with concentrated \(H_2SO_4\) forms a compound B which on addition of one mole of hydrogen in the presence of Ni forms a compound C. One mole of compound C on combustion forms two moles of \(CO_2\) and three moles of \(H_2O\). Identify the compounds A, B and C and write the chemical equations of the reactions involved.
Identification of compounds:
The combustion products indicate that compound C is \(C_2H_6\) (ethane).
Since C is formed by hydrogenation of B, B must be \(C_2H_4\) (ethene).
Compound A forms B on dehydration, so A is \(C_2H_5OH\) (ethanol).
Reactions involved:
1. Dehydration of ethanol:
\[ C_2H_5OH \xrightarrow{Hot\ conc.\ H_2SO_4} C_2H_4 + H_2O \]
2. Hydrogenation of ethene:
\[ C_2H_4 + H_2 \xrightarrow{Ni} C_2H_6 \]
3. Combustion of ethane:
\[ 2C_2H_6 + 7O_2 \rightarrow 4CO_2 + 6H_2O + \text{Heat} \]