Mix Examples - Carbon and its Compounds Questions in English

(N/A) Saturated hydrocarbons contain only carbon-carbon single bonds $(C-C)$.
Unsaturated hydrocarbons contain at least one carbon-carbon double $(C=C)$ or triple $(C\equiv C)$ bond.
Examples of Saturated hydrocarbons:
$1$. Methane $(CH_4)$: $H-C(H)(H)-H$
$2$. Ethane $(C_2H_6)$: $H_3C-CH_3$
Examples of Unsaturated hydrocarbons:
$1$. Ethene $(C_2H_4)$: $H_2C=CH_2$
$2$. Ethyne $(C_2H_2)$: $HC\equiv CH$

(N/A) functional group is an atom or a group of atoms joined in a specific manner that is responsible for the characteristic chemical properties of organic compounds.
Examples of four different functional groups are:
$1$. Hydroxyl group: $-OH$
$2$. Aldehyde group: $-CHO$
$3$. Carboxylic acid group: $-COOH$
$4$. Ketone group: $>C=O$

(N/A) The reaction used for the conversion of vegetable oils to fats is known as $Hydrogenation$.
$Hydrogenation$ is a chemical reaction in which hydrogen gas is added to unsaturated hydrocarbons (like vegetable oils containing double bonds) in the presence of a catalyst,such as $Nickel$ $(Ni)$,$Palladium$ $(Pd)$,or $Platinum$ $(Pt)$,to form saturated hydrocarbons (fats).
General reaction:
$R_2C=CR_2 + H_2 \xrightarrow{Ni \text{ catalyst}} R_2CH-CHR_2$
In this process,the $C=C$ double bond in the unsaturated oil molecule breaks,and two hydrogen atoms are added across the carbons,converting the liquid oil into a solid or semi-solid fat.

(N/A) The chemical formula of carbon tetrachloride is $CCl_4$.
In this molecule,one carbon atom shares its $4$ valence electrons with $4$ chlorine atoms,each contributing one electron to form $4$ covalent bonds.
Each chlorine atom completes its octet by sharing one electron with carbon,and the carbon atom completes its octet by sharing its $4$ electrons with the $4$ chlorine atoms.
The electron dot structure is as follows:
(The central Carbon atom is surrounded by four Chlorine atoms,with one shared pair of electrons between the Carbon and each Chlorine atom.)

(N/A) Saponification is the chemical process of converting an ester into a soap (a salt of a carboxylic acid) and an alcohol by treating it with an alkali like sodium hydroxide $(NaOH)$.
The general reaction is:
$CH_3COOC_2H_5 + NaOH \rightarrow CH_3COONa + C_2H_5OH$
(Ethyl acetate + Sodium hydroxide $\rightarrow$ Sodium acetate + Ethanol)

(N/A) Activity:
$1$. Take $1 \, mL$ of ethanol (absolute alcohol) and $1 \, mL$ of glacial acetic acid in a test tube.
$2$. Add a few drops of concentrated sulphuric acid to the mixture.
$3$. Warm the mixture in a water-bath at about $60 \, ^\circ C$ for at least $15 \, \text{min}$ as shown in the diagram. (Note: It should not be heated directly on a flame because ethanol is highly flammable).
$4$. Pour the contents into a beaker containing $20-50 \, mL$ of water and smell the resulting mixture. $A$ sweet,fruity smell indicates the formation of an ester.
Reaction:
$CH_3COOH + CH_3CH_2OH \xrightarrow{Conc. H_2SO_4} CH_3COOCH_2CH_3 + H_2O$
(Ethanoic acid + Ethanol $\rightarrow$ Ethyl ethanoate + Water)

(A) is Ethanoic acid $(CH_3COOH)$.
$R$ is Sodium acetate $(CH_3COONa)$ and the gas evolved is Hydrogen $(H_2)$.
$A$ is Methanol $(CH_3OH)$.
$S$ is Methyl acetate $(CH_3COOCH_3)$.
$(a)$ Reaction with $Na$ metal:
$2CH_3COOH + 2Na \to 2CH_3COONa + H_2 \uparrow$
$(b)$ Esterification reaction:
$CH_3COOH + CH_3OH \xrightarrow{Conc. H_2SO_4} CH_3COOCH_3 + H_2O$
$(c)$ Reaction with $NaOH$ (Neutralization):
$CH_3COOH + NaOH \to CH_3COONa + H_2O$
$(d)$ Saponification reaction:
$CH_3COOCH_3 + NaOH \to CH_3COONa + CH_3OH$

(N/A) The calcium hydroxide solution will turn milky due to the formation of calcium carbonate.
$(b)$ The chemical reactions are as follows:
In test tube $A$: Ethanoic acid reacts with sodium carbonate to produce carbon dioxide gas.
$2CH_{3}COOH + Na_{2}CO_{3} \rightarrow 2CH_{3}COONa + H_{2}O + CO_{2}$
In test tube $B$: Carbon dioxide gas reacts with calcium hydroxide (lime water) to form calcium carbonate,which makes the solution milky.
$Ca(OH)_{2} + CO_{2} \rightarrow CaCO_{3} + H_{2}O$
Note: If excess $CO_{2}$ is passed through the solution,the milkiness disappears due to the formation of soluble calcium bicarbonate.
$CaCO_{3} + H_{2}O + CO_{2} \rightarrow Ca(HCO_{3})_{2}$

(N/A) As $C_2H_5OH$ (ethanol) and $Na_2CO_3$ (sodium carbonate) do not react with each other,a similar change (effervescence due to $CO_2$ evolution) is not expected.
$C_2H_5OH + Na_2CO_3 \rightarrow$ No reaction
$(b)$ Lime water (calcium hydroxide solution) is prepared in the laboratory by dissolving a small amount of calcium oxide $(CaO)$ in water. The mixture is stirred and then allowed to settle. The clear supernatant liquid is then decanted or filtered to obtain the lime water solution.

(N/A) This conversion is achieved by the dehydration of ethanol using hot concentrated $H_2SO_4$,which acts as a dehydrating agent.
Reaction: $CH_3CH_2OH \xrightarrow[conc. H_2SO_4]{Hot} CH_2=CH_2 + H_2O$
$(b)$ This conversion is achieved by the oxidation of propanol using an oxidizing agent such as alkaline $KMnO_4$ or acidified $K_2Cr_2O_7$.
Reaction: $CH_3CH_2CH_2OH \xrightarrow[Heat]{Alk. KMnO_4} CH_3CH_2COOH$

(N/A) The molecular formula $C_3H_6O$ corresponds to two functional isomers:
$1$. Propanone $(CH_3COCH_3)$: $A$ ketone.
$2$. Propanal $(CH_3CH_2CHO)$: An aldehyde.
The electron dot structures are as follows:
- For Propanone: The central carbon atom is double-bonded to an oxygen atom and single-bonded to two methyl groups.
- For Propanal: The terminal carbon atom is double-bonded to an oxygen atom and single-bonded to a hydrogen atom and an ethyl group.

(N/A) Hydrogenation reaction: Unsaturated hydrocarbons add hydrogen in the presence of a nickel $(Ni)$ catalyst to form saturated hydrocarbons. Example: Ethene to Ethane.
$CH_2=CH_2 + H_2 \xrightarrow{Ni} CH_3-CH_3$
$(b)$ Oxidation reaction: Alcohols can be oxidized to carboxylic acids in the presence of oxidizing agents like alkaline potassium permanganate $(KMnO_4)$ or acidified potassium dichromate $(K_2Cr_2O_7)$ upon heating. Example: Ethanol to Ethanoic acid.
$CH_3CH_2OH \xrightarrow[Heat]{Alk. KMnO_4} CH_3COOH$
$(c)$ Substitution reaction: Saturated hydrocarbons are largely unreactive,but in the presence of sunlight $(hv)$,chlorine can replace hydrogen atoms one by one. Example: Methane to Chloromethane.
$CH_4 + Cl_2 \xrightarrow{hv} CH_3Cl + HCl$

(N/A) Saponification: It is the process of making soap by the alkaline hydrolysis of an ester. When an ester like ethyl acetate reacts with sodium hydroxide, it produces sodium acetate and ethanol.
$CH_{3}COOC_{2}H_{5} + NaOH \rightarrow CH_{3}COONa + C_{2}H_{5}OH$
$(b)$ Combustion: It is the process of burning a carbon compound in the presence of oxygen to release energy in the form of heat and light. For example, the combustion of methane:
$CH_{4} + 2O_{2} \rightarrow CO_{2} + 2H_{2}O + \text{Heat and Light}$

(A) Since one mole of compound $C$ gives $2$ moles of $CO_2$ and $3$ moles of $H_2O$, its molecular formula is $C_2H_6$ (Ethane).
Compound $C$ is obtained by the hydrogenation of compound $B$, so $B$ must be $C_2H_4$ (Ethene).
Compound $B$ is formed by the dehydration of compound $A$ using concentrated $H_2SO_4$, which indicates $A$ is an alcohol, specifically $C_2H_5OH$ (Ethanol).
Reaction $1$: $C_2H_5OH \xrightarrow{\text{Hot conc. } H_2SO_4} C_2H_4 + H_2O$
Reaction $2$: $C_2H_4 + H_2 \xrightarrow{Ni} C_2H_6$
Reaction $3$: $2C_2H_6 + 7O_2 \to 4CO_2 + 6H_2O + \text{Heat and light}$

(B) The chemical formula $C_{3}H_{6}$ corresponds to the general formula $C_{n}H_{2n}$,which is characteristic of alkenes.
Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond.
Bromine water is a standard test for unsaturation; it turns from reddish-brown to colourless in the presence of alkenes or alkynes.
Since the compound is an alkene with $3$ carbon atoms,its name is propene $\left(H_{3}C-CH=CH_{2}\right)$.

(N/A) The aldehyde with four carbon atoms is known as Butanal.
Its structural formula is $CH_{3}-CH_{2}-CH_{2}-CHO$.

(N/A) Methanoic acid is the simplest carboxylic acid with the chemical formula $HCOOH$.
Its structural formula consists of a carbon atom double-bonded to an oxygen atom,single-bonded to a hydroxyl group $(-OH)$,and single-bonded to a hydrogen atom.
The structure is represented as:
$H - C(=O) - OH$

(C) The nitrogen atom in an ammonia molecule $(NH_{3})$ has an atomic number of $7$,with an electronic configuration of $2, 5$. To achieve a stable octet,nitrogen requires $3$ more electrons. It shares these $3$ electrons with $3$ hydrogen atoms,forming $3$ covalent bonds. Therefore,there are $3$ bonds present around the nitrogen atom.

(C) The chemical formula of ethane is $C_2H_6$.
In an ethane molecule,there is one $C-C$ single covalent bond.
There are six $C-H$ single covalent bonds (three for each carbon atom).
Therefore,the total number of covalent bonds in ethane is $1 + 6 = 7$.

(B) Unsaturated hydrocarbons (like alkenes and alkynes) have a higher percentage of carbon compared to saturated hydrocarbons.
When they burn in air,the oxygen available is often insufficient for complete combustion.
Due to the high carbon content,the carbon atoms do not get fully oxidized to $CO_2$,leading to the formation of unburnt carbon particles (soot).
These incandescent carbon particles glow with a yellow flame and are released as black smoke.

(N/A) Butane has the chemical formula $C_{4}H_{10}$.
When one hydrogen atom is replaced by a hydroxyl group $(-OH)$,it forms an alcohol.
The molecular formula for butanol is $C_{4}H_{9}OH$ or $CH_{3}CH_{2}CH_{2}CH_{2}OH$.

(C) Carbon has an atomic number of $6$ and an electronic configuration of $(2, 4)$.
It has $4$ electrons in its outermost shell.
To attain a stable noble gas configuration (octet),it requires $4$ more electrons.
Since it is difficult to lose or gain $4$ electrons due to energy constraints,carbon achieves stability by sharing its $4$ valence electrons with other atoms to form covalent bonds.

(N/A) The functional group $-COOH$ present in citric acid is known as the Carboxylic acid group. It is a characteristic functional group found in organic acids,where a carbon atom is double-bonded to an oxygen atom and single-bonded to a hydroxyl group $(-OH)$.

(N/A) The general formula for an alkane is $C_{n}H_{2n+2}$,where $n$ is the number of carbon atoms.
Given that the molecule contains $n = 4$ carbon atoms.
Substituting $n = 4$ into the formula: $C_{4}H_{2(4)+2} = C_{4}H_{8+2} = C_{4}H_{10}$.
The alkane with four carbon atoms is named Butane.

(N/A) $(i)$ The compound $CH_{3}-CH_{2}-CH_{2}-COOH$ contains the $-COOH$ group,which is a Carboxylic acid functional group.
$(ii)$ The compound $CH_{3}-CO-CH_{2}-CH_{3}$ contains the $C=O$ group bonded to two carbon atoms,which is a Ketone functional group.

(4) $(i)$ In an alkane,each carbon atom is bonded to four other atoms through single covalent bonds,so its valency is $4$.
$(ii)$ In an alkyne,each carbon atom involved in the triple bond is bonded to two other atoms,maintaining a total valency of $4$.

(N/A) $(i)$ The molecular formula of benzene is $C_{6}H_{6}$.
$(ii)$ It contains three double bonds in its structure.

(N/A) The two characteristic features of carbon that lead to the formation of a vast number of carbon compounds are:
$(i)$ Catenation: The unique ability of carbon atoms to form bonds with other carbon atoms,giving rise to large molecules (chains,branched chains,or rings).
$(ii)$ Tetravalency: Carbon has a valency of $4$,which allows it to bond with four other atoms of carbon or atoms of other monovalent elements like hydrogen,oxygen,nitrogen,sulfur,chlorine,etc.

(A) For $A$ $(C_{10}H_{18})$: The general formula for an alkyne is $C_nH_{2n-2}$. Here,$n = 10$,so $2n - 2 = 2(10) - 2 = 18$. Thus,$A$ belongs to the alkyne homologous series.
For $B$ $(C_{18}H_{36})$: The general formula for an alkene is $C_nH_{2n}$. Here,$n = 18$,so $2n = 2(18) = 36$. Thus,$B$ belongs to the alkene homologous series.

(N/A) homologous series is a group of organic compounds having the same functional group and similar chemical properties,where each successive member differs by a $CH_{2}$ unit.
$1$. For $CH_{3}CH_{2}OH$ (Ethanol),the next homologue is obtained by adding a $CH_{2}$ group,which results in $CH_{3}CH_{2}CH_{2}OH$ (Propan$-1-$ol).
$2$. For $HCOOH$ (Methanoic acid),the next homologue is obtained by adding a $CH_{2}$ group,which results in $CH_{3}COOH$ (Ethanoic acid).
Therefore,the next homologues are Propanol and Ethanoic acid respectively.

(A-D) $(i)$ The compound $CH_{3}-CH_{2}-CH=CH_{2}$ has four carbon atoms and a double bond,so it is named But-$1$-ene.
$(ii)$ The compound $CH_{3}-CH_{2}-CH_{2}-C(CH_{3})_{2}-CH_{3}$ has a five-carbon chain with two methyl groups at the second position from the end,so it is named $2,2$-Dimethylpentane.
$(iii)$ The compound $CH_{3}-CH_{2}-CHO$ has three carbon atoms and an aldehyde functional group,so it is named Propanal.
$(iv)$ The compound $CH_{3}-CH(OH)-CH_{3}$ has three carbon atoms and an alcohol functional group at the second carbon,so it is named Propan-$2$-ol.

(B) Micelle formation will not take place when soap is dissolved in an organic solvent.
Soap molecules consist of a hydrophobic hydrocarbon tail and a hydrophilic ionic head.
In an aqueous solution,the hydrophobic tails aggregate to avoid water,while the hydrophilic heads interact with water,leading to micelle formation.
In an organic solvent,the hydrophobic tails are soluble,so there is no driving force for the molecules to aggregate into a micelle structure.

(N/A) Hard water contains dissolved salts of calcium $(Ca^{2+})$ and magnesium $(Mg^{2+})$ ions. When soap is added to hard water,these ions react with the soap molecules to form an insoluble precipitate known as scum. Because the soap is consumed in forming this scum,it is unable to form a lather with the water,which is necessary for cleaning clothes. Consequently,a large amount of soap is wasted,and the cleaning process becomes ineffective.

(A) When a small piece of sodium metal is added to ethanol,it reacts to produce sodium ethoxide and hydrogen gas. The hydrogen gas is released as bubbles.
$2Na + 2C_{2}H_{5}OH \to 2C_{2}H_{5}ONa + H_{2} \uparrow$

(N/A) The simplest ketone is acetone,also known as propanone. Its chemical formula is $CH_3COCH_3$. The structure consists of a central carbonyl group $(C=O)$ bonded to two methyl groups $(CH_3)$.
Structure:
$CH_3 - C(=O) - CH_3$

(N/A) When $5\%$ alkaline $KMnO_4$ solution is added drop by drop to warm ethanol,the initial pink colour of the potassium permanganate solution disappears. This happens because the alkaline $KMnO_4$ acts as an oxidising agent and oxidises ethanol to ethanoic acid. The chemical reaction is: $CH_3CH_2OH + [O] \xrightarrow{\text{alkaline } KMnO_4} CH_3COOH + H_2O$. The name of the compound formed is Ethanoic acid.

(N/A) Saturated hydrocarbons contain a lower percentage of carbon and have a higher hydrogen-to-carbon ratio, which allows for complete combustion in the presence of sufficient oxygen, resulting in a clean blue flame.
In contrast, unsaturated hydrocarbons have a higher percentage of carbon and a lower hydrogen-to-carbon ratio.
Due to this, they do not undergo complete combustion even in the presence of sufficient oxygen, leading to the formation of unburnt carbon particles.
These unburnt carbon particles glow and make the flame sooty or yellow.

(B) When soap reacts with hard water,the minerals present in the water,specifically calcium and magnesium ions,react with the soap molecules.
This reaction results in the formation of an insoluble white curdy precipitate known as scum.
Because the soap is consumed in forming this scum,it significantly reduces the cleaning efficiency of the soap.

(N/A) To draw the electron dot structure of ethane $(C_{2}H_{6})$:
$1$. Ethane consists of two carbon atoms bonded together by a single covalent bond.
$2$. Each carbon atom is further bonded to three hydrogen atoms.
$3$. Carbon has $4$ valence electrons and hydrogen has $1$ valence electron.
$4$. Each carbon atom shares one electron with the other carbon atom and one electron with each of the three hydrogen atoms to complete its octet.
$5$. The structure is represented as:
$H \quad H$
$| \quad |$
$H-C-C-H$
$| \quad |$
$H \quad H$
The electron dot structure is:
$H \quad H$
$.. \quad ..$
$H : C : C : H$
$.. \quad ..$
$H \quad H$

(N/A) Carbon compounds are generally covalent in nature,meaning they are formed by the sharing of electrons between atoms. Because they do not dissociate into ions or charged particles when dissolved in water or in a molten state,they lack the free charge carriers necessary to conduct electricity.

(B) homologous series is a group of organic compounds having the same functional group and similar chemical properties,where each successive member differs by a $CH_{2}$ unit.
$1$. $C_{2}H_{6}O$ can represent ethanol $(C_{2}H_{5}OH)$.
$2$. $CH_{4}O$ represents methanol $(CH_{3}OH)$.
Both compounds contain the same functional group,which is the hydroxyl group $(-OH)$.
Since they belong to the alcohol homologous series,$C_{2}H_{6}O$ and $CH_{4}O$ are the correct pair.

(B) The melting point of pure ethanoic acid is $290 \,K$ $(17 \,^{\circ}C)$.
Because this temperature is close to room temperature in cold climates,it often freezes during winter.
When it freezes,it forms solid,ice-like flakes or crystals,which is why it is commonly referred to as glacial acetic acid.

(N/A) In a homologous series of alkanes,each successive member differs from the previous one by a $-CH_2-$ group.
$(i)$ The difference in molecular mass is calculated as: $(1 \times 12) + (2 \times 1) = 14 \ u$.
$(ii)$ The difference in the number of atoms is one carbon atom and two hydrogen atoms,represented by the group $-CH_2-$.

(N/A) $(i)$ Covalent compounds are bad conductors of electricity because the bonding in these compounds does not give rise to any charged ions.
$(ii)$ Covalently bonded molecules have strong covalent bonds within the molecule,but the intermolecular forces of attraction between the molecules are very weak,which results in low melting and boiling points.

(N/A) $(i)$ $A$ homologous series is a group of organic compounds having the same functional group and similar chemical properties,in which all successive members differ by a $-CH_{2}$ unit.
$(ii)$ The melting and boiling points of $C_{5}H_{10}$ are higher than those of $C_{4}H_{8}$ because the molecular mass of $C_{5}H_{10}$ is greater than that of $C_{4}H_{8}$. As molecular mass increases,the intermolecular forces of attraction increase,requiring more energy to overcome them.
$(iii)$ The order of increasing boiling points is: $C_{3}H_{6} < C_{4}H_{8} < C_{5}H_{10}$.

(C) $(i)$ Compounds $A, B$ and $C$ are unsaturated hydrocarbons containing a carbon-carbon double bond.
$(ii)$ The boiling point of members of a homologous series increases with an increase in molecular mass (i.e.,an increase in the number of carbon atoms). Since compound $C$ has the lowest boiling point,it must have the minimum number of carbon atoms.
$(iii)$ The general formula $C_{n}H_{2n}$ represents the homologous series of alkenes.

(N/A) $(i)$ Covalent compounds have low melting and boiling points.
$(ii)$ Covalent compounds do not conduct electricity.

(N/A) $(i)$ Silicon is the element that exhibits the property of catenation up to seven or eight atoms.
$(ii)$ No,these compounds are not stable because they are highly reactive,especially in the presence of oxygen or moisture,due to the weak $Si-Si$ bond compared to the $C-C$ bond.

(A) Alkenes follow the general formula $C_{n}H_{2n}$.
$C_{2}H_{4}$ $(n=2)$ and $C_{4}H_{8}$ $(n=4)$ fit this formula,so they are alkenes.
Alkynes follow the general formula $C_{n}H_{2n-2}$.
$C_{3}H_{4}$ $(n=3)$ and $C_{2}H_{2}$ $(n=2)$ fit this formula,so they are alkynes.

(N/A) $(i)$ When ethanol is burnt in air,it undergoes combustion to produce carbon dioxide,water,and energy.
$CH_{3}CH_{2}OH + 3O_{2} \longrightarrow 2CO_{2} + 3H_{2}O + \text{Energy}$
$(ii)$ When ethanol is oxidized using oxidizing agents like alkaline $KMnO_{4}$ or acidified $K_{2}Cr_{2}O_{7}$,it is converted into ethanoic acid.
$CH_{3}CH_{2}OH \xrightarrow[\text{Acidified } K_{2}Cr_{2}O_{7}]{\text{Alkaline } KMnO_{4}} CH_{3}COOH$