Question 1

Q1: Ethane, with the molecular formula $\mathrm{C}_{2} \mathrm{H}_{6}$ has (a) 6 covalent bonds. (b) 7 covalent bonds. (c) 8 covalent bonds. (d) 9 covalen...

Accepted Answer

The correct answer is (b) 7 covalent bonds. Explanation: The structure of ethane ($\mathrm{C}_{2} \mathrm{H}_{6}$) is: CC To determine the number of covalent bonds, we count all the single bonds between the atoms: - There is one single covalent bond between the two carbon atoms (C-C). - There are si...

Question 2

Q10: Explain the formation of scum when hard water is treated with soap.

Accepted Answer

Hard water contains dissolved salts of calcium ($\mathrm{Ca}^{2+}$) and magnesium ($\mathrm{Mg}^{2+}$) ions. Soap consists of sodium or potassium salts of long-chain carboxylic acids (fatty acids). For example, sodium stearate ($\mathrm{C}_{17} \mathrm{H}_{35} \mathrm{COONa}$). When soap is added to...

Question 3

Q11: What change will you observe if you test soap with litmus paper (red and blue)?

Accepted Answer

Soaps are salts of a strong base (like NaOH or KOH) and a weak acid (a long-chain carboxylic acid). When soap is dissolved in water, it undergoes hydrolysis, which produces a small amount of hydroxide ions ($\mathrm{OH}^{-}$), making the solution slightly alkaline or basic. Because the soap solution...

Question 4

Q12: What is hydrogenation? What is its industrial application?

Accepted Answer

Hydrogenation: Hydrogenation is a chemical reaction that involves the addition of hydrogen ($\mathrm{H}_{2}$) across a double or triple bond in an unsaturated organic compound. This reaction is typically carried out in the presence of a metal catalyst, such as nickel (Ni), palladium (Pd), or platinu...

Question 5

Q13: Which of the following hydrocarbons undergo addition reactions: $\mathrm{C}_{2} \mathrm{H}_{6}, \mathrm{C}_{3} \mathrm{H}_{8}, \mathrm{C}_{3} \mathrm{...

Accepted Answer

Addition reactions are characteristic of unsaturated hydrocarbons, which are compounds containing double or triple bonds between carbon atoms (alkenes and alkynes). Let us analyze the given hydrocarbons: -   $\mathrm{C}_{2} \mathrm{H}_{6}$ (Ethane): Follows the general formula $\mathrm{C}_{n} \mathr...

Question 6

Q14: Give a test that can be used to differentiate between saturated and unsaturated hydrocarbons.

Accepted Answer

A common test to differentiate between saturated and unsaturated hydrocarbons is the Bromine Water Test. Procedure: 1.  Take two test tubes, one containing the saturated hydrocarbon (e.g., hexane) and the other containing the unsaturated hydrocarbon (e.g., hexene). 2.  Add a few drops of bromine wat...

Question 7

Q15: Explain the mechanism of the cleaning action of soaps.

Accepted Answer

The cleaning action of soap is based on the unique structure of its molecules, which allows them to act as an emulsifying agent between oil and water. 1.  Structure of a Soap Molecule: A soap molecule has two parts:        A hydrophobic tail: A long hydrocarbon chain that is repelled by water but at...

Question 8

Q2: Butanone is a four-carbon compound with the functional group (a) carboxylic acid. (b) aldehyde. (c) ketone. (d) alcohol.

Accepted Answer

The correct answer is (c) ketone. Explanation: - The prefix "but-" indicates that the compound has a chain of four carbon atoms. - The suffix "-one" is used to denote the presence of a ketone functional group ($>C=O$). Therefore, butanone is a four-carbon compound containing a ketone functional grou...

Question 9

Q3: While cooking, if the bottom of the vessel is getting blackened on the outside, it means that (a) the food is not cooked completely. (b) the fuel is n...

Accepted Answer

The correct answer is (b) the fuel is not burning completely. Explanation: When a fuel burns in an insufficient supply of oxygen (air), it undergoes incomplete combustion. This process produces soot, which is essentially unburnt carbon. This black soot gets deposited on the bottom of the cooking ves...

Question 10

Q4: Explain the nature of the covalent bond using the bond formation in $\mathrm{CH}_{3} \mathrm{Cl}$.

Accepted Answer

A covalent bond is a chemical bond formed by the mutual sharing of electrons between atoms to achieve a stable electron configuration, similar to that of a noble gas. In the formation of chloromethane ($\mathrm{CH}_{3} \mathrm{Cl}$): 1.  Valence Electrons:        Carbon (C) has 4 valence electrons....

Question 11

Q5: Draw the electron dot structures for (a) ethanoic acid. (b) $\mathrm{H}_{2} \mathrm{S}$. (c) propanone. (d) $\mathrm{F}_{2}$.

Accepted Answer

(a) Ethanoic acid ($\mathrm{CH}_{3} \mathrm{COOH}$): CC(=O)O Electron Dot Structure:  (b) Hydrogen Sulphide ($\mathrm{H}_{2} \mathrm{S}$): S Electron Dot Structure:  (c) Propanone ($\mathrm{CH}_{3} \mathrm{COCH}_{3}$): CC(C)=O Electron Dot Structure:  (d) Fluorine molecule ($\mathrm{F}_{2}$): FF Ele...

Question 12

Q6: What is an homologous series? Explain with an example.

Accepted Answer

A homologous series is a series of organic compounds that have the same functional group and similar chemical properties. The successive members of the series differ from each other by a $-\mathrm{CH}_{2}$ group. Characteristics of a homologous series: 1.  All members can be represented by the same...

Question 13

Q7: How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?

Accepted Answer

Ethanol and ethanoic acid can be differentiated based on the following properties: Physical Properties: | Property | Ethanol ($\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$) | Ethanoic Acid ($\mathrm{CH}_{3} \mathrm{COOH}$) | | :--- | :--- | :--- | | Smell | Pleasant, characteristic alcoholic smell. |...

Question 14

Q8: Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?

Accepted Answer

Micelle Formation in Water: Micelle formation occurs when soap is dissolved in water due to the unique structure of soap molecules. A soap molecule has two distinct parts: 1.  A long hydrocarbon chain: This part is hydrophobic (water-repelling) and lipophilic (oil-attracting). 2.  An ionic end (e.g....

Question 15

Q9: Why are carbon and its compounds used as fuels for most applications?

Accepted Answer

Carbon and its compounds are widely used as fuels for several reasons: 1.  High Calorific Value: Most carbon compounds, especially hydrocarbons like those in LPG, petrol, and diesel, release a large amount of heat energy per unit of mass when they undergo combustion. This makes them efficient source...

NCERT Solutions