NCERT Class 10 Science Solutions: Carbon and Its Compounds

Question:

The question is about determining the number of covalent bonds in a molecule of ethane (C2H6). To solve this, one needs to understand how to draw the Lewis structure of a molecule, which involves representing the sharing of electrons between atoms to form covalent bonds. Each covalent bond is formed by sharing one pair of electrons. Single bonds, double bonds, and triple bonds are all types of covalent bonds.


Ethane has the molecular formula C2H6. This means it contains two carbon atoms and six hydrogen atoms. In ethane, each carbon atom is bonded to the other carbon atom and to hydrogen atoms. To determine the number of covalent bonds, we draw the Lewis structure of ethane. Carbon has 4 valence electrons, and hydrogen has 1 valence electron.
In ethane, the two carbon atoms form a single covalent bond between themselves. Each carbon atom then forms single covalent bonds with three hydrogen atoms. So, the structure looks like this:
H H
| |
H – C – C – H
| |
H H
Let’s count the covalent bonds:
1. Carbon-Carbon single bond: 1 covalent bond
2. Carbon-Hydrogen single bonds: Each carbon atom is bonded to 3 hydrogen atoms, so there are 3 C-H bonds on the first carbon and 3 C-H bonds on the second carbon. This gives a total of 3 + 3 = 6 covalent bonds.
Total number of covalent bonds = 1 (C-C bond) + 6 (C-H bonds) = 7 covalent bonds.

Therefore, ethane has 7 covalent bonds.

The final answer is $\boxed{7}$.

Question:

Combustion is the process of burning a fuel to produce heat and light. Complete combustion of a fuel occurs when there is sufficient oxygen and the fuel burns with a clean, blue flame, producing primarily carbon dioxide and water. Incomplete combustion occurs when there is insufficient oxygen or other factors, resulting in the formation of soot (carbon particles) and carbon monoxide, in addition to carbon dioxide and water. Soot is the black residue that causes the blackening of the vessel.


When the bottom of a cooking vessel gets blackened on the outside, it indicates the deposition of soot. Soot is a byproduct of incomplete combustion of the fuel. Incomplete combustion happens when the fuel does not burn completely due to insufficient supply of oxygen. If the fuel were burning completely, it would produce a clean blue flame and little to no soot, thus not blackening the vessel. The food not being cooked completely or the fuel being wet are not direct causes of the blackening, although a wet fuel might contribute to incomplete combustion. The primary reason for the blackening is the incomplete burning of the fuel, which releases unburnt carbon particles (soot).

Therefore, the correct answer is that the fuel is not burning completely.

The final answer is $\boxed{B}$.

Question:

Understanding IUPAC nomenclature for organic compounds, specifically identifying functional groups based on the name and structure. The prefixes in organic names (e.g., but-) indicate the number of carbon atoms, and the suffix (e.g., -one) indicates the type of functional group.


The question asks to identify the functional group of butanone. Let’s break down the name “butanone”.
The prefix “but-” indicates that the compound has four carbon atoms.
The suffix “-one” is the characteristic ending for a ketone functional group. Ketones have a carbonyl group (C=O) bonded to two alkyl groups.

Let’s consider the options:
A. Carboxylic acid: These have the functional group -COOH and end with “-oic acid” in IUPAC nomenclature (e.g., butanoic acid).
B. Aldehyde: These have the functional group -CHO and end with “-al” in IUPAC nomenclature (e.g., butanal).
C. Ketone: These have the functional group R-CO-R’ and end with “-one” in IUPAC nomenclature. Butanone is a specific example of a ketone.
D. Alcohol: These have the functional group -OH and end with “-ol” in IUPAC nomenclature (e.g., butanol).

Therefore, butanone has a ketone functional group.

The final answer is $\boxed{C}$.

Question:

The question asks to name an organic compound based on its structural formula. The key concepts needed are:
1. Identification of functional groups.
2. Understanding of nomenclature rules for aldehydes.


The given structural formula is H | H−C=O.

First, let’s interpret the structure.
H |
H−C=O

This structure represents a carbon atom bonded to one hydrogen atom, a double bond with an oxygen atom, and another bond to a hydrogen atom.

Now, let’s identify the functional group present.
The presence of a carbon atom double-bonded to an oxygen atom (C=O) and also bonded to at least one hydrogen atom (-H) indicates the presence of an aldehyde functional group. The general formula for an aldehyde is R-CHO, where R is an alkyl group or a hydrogen atom.

In this specific case, R is a hydrogen atom (H). So, the compound is H-CHO.

Next, we apply the IUPAC nomenclature rules for aldehydes.
1. The parent hydrocarbon is determined by the longest carbon chain containing the aldehyde group. In H-CHO, there is only one carbon atom. A one-carbon alkane is methane.
2. The suffix for aldehydes is ‘-al’.
3. The ‘-e’ ending of the parent alkane is replaced by ‘-al’.

So, for methane, the name becomes methanal.

The common name for H-CHO is formaldehyde. However, the question asks “How would you name the following compound?”, implying the standard systematic (IUPAC) name is expected.

Therefore, the name of the compound is methanal.

Step-by-step derivation:
1. Identify the functional group: The C=O group bonded to a hydrogen atom is an aldehyde.
2. Determine the number of carbon atoms in the longest chain containing the functional group: There is 1 carbon atom.
3. Identify the parent alkane: A one-carbon alkane is methane.
4. Apply the aldehyde suffix: Replace the ‘e’ of methane with ‘al’.
5. Combine to get the IUPAC name: Methanal.

Question:

Nomenclature of Alkyne:
1. Identify the longest carbon chain containing the triple bond. This chain determines the parent alkane name.
2. Number the carbon chain such that the triple bond gets the lowest possible number.
3. The suffix “-yne” replaces the “-ane” suffix of the parent alkane.
4. Indicate the position of the triple bond by the number of the first carbon atom of the triple bond.
5. If there are substituents, name and number them according to IUPAC rules.


The given compound is a hydrocarbon with a triple bond.
First, let’s draw the complete structure for clarity:
H H H H
| | | |
H – C – C – C – C – C ≡ C – H
| | | |
H H H H

1. Identify the longest carbon chain containing the triple bond. In this molecule, the longest continuous chain of carbon atoms that includes the triple bond has 6 carbon atoms. Therefore, the parent alkane name is hexane.

2. Number the carbon chain to give the triple bond the lowest possible number. If we number from left to right, the triple bond starts at carbon 5. If we number from right to left, the triple bond starts at carbon 1. Therefore, we should number from right to left.
H – C – C – C – C – C ≡ C – H
6 5 4 3 2 1

3. Replace the “-ane” suffix of the parent alkane with “-yne” to indicate the presence of a triple bond. So, hexane becomes hexyne.

4. Indicate the position of the triple bond by the number of the first carbon atom of the triple bond. The triple bond starts at carbon 1. So, it is 1-hexyne.

5. Check for any substituents. In this molecule, there are no substituent groups attached to the main carbon chain. The carbons at positions 2, 3, 4, 5, and 6 are fully saturated with hydrogen atoms, forming methyl and methylene groups as part of the chain.

Therefore, the name of the compound is 1-hexyne.

Question:

Alkanes are saturated hydrocarbons with the general formula CnH2n+2. Alkanals are aldehydes derived from alkanes, characterized by the presence of a formyl group (-CHO) at the end of a carbon chain. The prefix “hex-” indicates a six-carbon chain.


The name “Hexanal” tells us two important things:
1. “Hex-” signifies a parent carbon chain containing six carbon atoms.
2. “-al” signifies that the functional group is an aldehyde. An aldehyde has a carbonyl group (C=O) bonded to at least one hydrogen atom, represented as -CHO. This -CHO group is always at the terminal position (the end) of the carbon chain.

To draw the structure of Hexanal, we follow these steps:
1. Draw a chain of six carbon atoms.
C – C – C – C – C – C
2. Identify the terminal carbon. In an aldehyde, the -CHO group is at one end. We can pick either end. Let’s pick the rightmost carbon.
3. Attach the aldehyde functional group (-CHO) to this terminal carbon. This means the terminal carbon is double-bonded to an oxygen atom and single-bonded to a hydrogen atom.
C – C – C – C – C – C(=O)H
4. Now, fill in the remaining bonds for the other carbon atoms with hydrogen atoms to satisfy the valency of each carbon (which is 4).
* The second-to-last carbon is bonded to two other carbons, so it needs two hydrogen atoms.
* The carbons in the middle of the chain are bonded to two other carbons, so they each need two hydrogen atoms.
* The first carbon (on the left) is bonded to only one other carbon, so it needs three hydrogen atoms.

Therefore, the structure of Hexanal is:
CH3 – CH2 – CH2 – CH2 – CH2 – CHO

Or, showing all the bonds explicitly:
H H H H H O
| | | | | //
H – C – C – C – C – C – C
| | | | | \
H H H H H H

Question:

Combustion, energy release, carbon compounds as fuels, properties of carbon.


Carbon and its compounds are extensively used as fuels for several key reasons, primarily related to their ability to undergo combustion and release significant amounts of energy.

Firstly, carbon compounds, especially hydrocarbons (compounds of carbon and hydrogen), are readily available and have been formed over geological time from the remains of ancient organisms. This natural abundance makes them economically viable sources of energy.

Secondly, carbon has a unique ability to form strong covalent bonds with itself and other elements like hydrogen, oxygen, and nitrogen. This allows for the formation of a vast array of complex and stable molecules. When these carbon compounds undergo combustion (a rapid reaction with oxygen), these strong bonds are broken, and new, more stable bonds are formed, releasing a considerable amount of energy in the form of heat and light. This energy release is the fundamental reason why they are effective fuels.

Thirdly, the combustion of many carbon compounds produces relatively safe byproducts. For example, the primary products of hydrocarbon combustion are carbon dioxide and water. While excessive carbon dioxide contributes to climate change, these products are generally less harmful and easier to manage compared to the byproducts of some other potential fuel sources.

Finally, the energy content of carbon fuels is high. This means that a small amount of fuel can produce a large amount of energy, making them efficient for powering vehicles, heating homes, and running industries. The controlled burning of these compounds allows for efficient energy extraction and utilization.

Question:

To draw electron dot structures (Lewis structures), we need to understand the valency of atoms, the concept of valence electrons, and the octet rule (or duet rule for hydrogen). The number of valence electrons determines how many bonds an atom can form and how many lone pairs it will have.


1. Identify the central atom: In H₂S, sulfur (S) is less electronegative than hydrogen (H), so sulfur is the central atom.
2. Count the total number of valence electrons:
* Sulfur (Group 16) has 6 valence electrons.
* Hydrogen (Group 1) has 1 valence electron each. Since there are two hydrogen atoms, they contribute 2 * 1 = 2 valence electrons.
* Total valence electrons = 6 (from S) + 2 (from 2H) = 8 valence electrons.
3. Connect the outer atoms to the central atom with single bonds: Place the two hydrogen atoms around the sulfur atom and connect them with single bonds. Each single bond uses 2 electrons.
* H – S – H
* Electrons used = 2 (for S-H bond) + 2 (for S-H bond) = 4 electrons.
4. Distribute the remaining electrons as lone pairs on the central atom:
* Remaining electrons = Total valence electrons – Electrons used in bonds = 8 – 4 = 4 electrons.
* Place these 4 electrons as lone pairs on the sulfur atom. Sulfur will have 2 lone pairs.
5. Check if the octet rule is satisfied for all atoms:
* Each hydrogen atom has 2 electrons (from the single bond), satisfying the duet rule.
* The sulfur atom has 4 electrons from the two single bonds and 4 electrons from the two lone pairs, totaling 8 electrons, satisfying the octet rule.

Electron Dot Structure:
. .
: S :
‘ ‘
/ \
H H

Question:

Understanding the definition of an alkane and alkyl halide. Knowing how to represent structural formulas of organic compounds. Recognizing the concept of structural isomerism, which involves compounds with the same molecular formula but different structural arrangements of atoms.


Bromopentane is an alkyl halide derived from pentane. Pentane has the molecular formula C5H12. When a bromine atom replaces one of the hydrogen atoms, it forms bromopentane, which has the molecular formula C5H11Br.

To draw the structure of bromopentane, we first draw the carbon chain of pentane and then attach a bromine atom to one of the carbon atoms. Pentane is a five-carbon alkane.

There are three possible positions for the bromine atom on the pentane chain, leading to different structural isomers.

Possibility 1: Bromine is attached to the first carbon atom.
This gives 1-bromopentane.
Structure: CH3-CH2-CH2-CH2-CH2-Br

Possibility 2: Bromine is attached to the second carbon atom.
This gives 2-bromopentane.
Structure: CH3-CHBr-CH2-CH2-CH3

Possibility 3: Bromine is attached to the third carbon atom.
This gives 3-bromopentane.
Structure: CH3-CH2-CHBr-CH2-CH3

Note that attaching the bromine to the fourth carbon would result in 4-bromopentane, which is the same as 2-bromopentane due to symmetry (counting from the other end of the chain gives 2-bromopentane). Similarly, attaching to the fifth carbon would be 1-bromopentane.

Therefore, structural isomers are possible for bromopentane. The possible structural isomers are 1-bromopentane, 2-bromopentane, and 3-bromopentane.

Question:

Oxidation is a chemical process that involves the gain of oxygen atoms, the loss of hydrogen atoms, or an increase in the oxidation state of an atom. In organic chemistry, the conversion of alcohols to carboxylic acids is a common example of oxidation.


Ethanol (an alcohol) has the chemical formula CH3CH2OH. Ethanoic acid (a carboxylic acid) has the chemical formula CH3COOH.

Let’s examine the changes in the molecule:
In ethanol, the carbon atom bonded to the hydroxyl group (-OH) is bonded to one other carbon atom and two hydrogen atoms.
In ethanoic acid, this same carbon atom is now bonded to the hydroxyl group, the other carbon atom, and two oxygen atoms (one double bond to oxygen and one single bond to the hydroxyl oxygen).

Comparing the two structures:
Ethanol: CH3-CH2-OH
Ethanoic acid: CH3-C(=O)-OH

We can see that during the conversion of ethanol to ethanoic acid:
1. An oxygen atom has been added to the carbon atom that was part of the ethyl group. Specifically, the -CH2-OH group becomes a -COOH group.
2. Hydrogen atoms have been removed. Two hydrogen atoms from the -CH2- group and the hydrogen atom from the -OH group are effectively removed and combined with the added oxygen to form water as a byproduct.

Since there is a gain of oxygen and a loss of hydrogen, this process is classified as an oxidation reaction. The carbon atom in the functional group changes its oxidation state from -1 in ethanol to +3 in ethanoic acid, further confirming it as an oxidation.

Question:

Isomers are molecules with the same molecular formula but different structural formulas. Structural isomers differ in the arrangement of atoms. For alkanes, structural isomerism arises from branching of the carbon chain.


The molecular formula for pentane is C5H12.
We need to find different ways to arrange these 5 carbon atoms and 12 hydrogen atoms.

Step 1: Draw the straight-chain isomer.
This is n-pentane, where all 5 carbon atoms are in a single, unbranched chain.
CH3-CH2-CH2-CH2-CH3

Step 2: Consider a chain of 4 carbon atoms with a methyl (CH3) group as a branch.
We can attach the methyl group to the second carbon atom of the 4-carbon chain. Attaching it to the first or last carbon would result in a straight chain of 5 carbons again, which we’ve already covered.
CH3
|
CH3-CH-CH2-CH3
This isomer is called isopentane (or 2-methylbutane).

Step 3: Consider a chain of 3 carbon atoms with two methyl groups as branches.
If we attach both methyl groups to the middle carbon of a 3-carbon chain, we get a highly branched structure.
CH3
|
CH3-C-CH3
|
CH3
This isomer is called neopentane (or 2,2-dimethylpropane).

Step 4: Check for other possibilities.
A chain of 2 carbon atoms would require 3 methyl groups to make 5 carbons total, but this arrangement is not possible to form a stable molecule with the correct valency. Similarly, a chain of 1 carbon atom is not possible.

Therefore, there are three structural isomers of pentane.

Answer: 3

Question:

Homologous series refers to a group of organic compounds that have the same general formula and similar chemical properties. They differ from each other by a repeating unit, typically a methylene (-CH2-) group.


A homologous series is a sequence of compounds with the same functional group and general formula, in which successive members differ by a CH2 group.

Key characteristics of a homologous series:
1. All members have the same functional group.
2. All members have the same general formula.
3. Successive members differ by a -CH2- unit.
4. There is a gradual change in physical properties (like boiling point, melting point, density) with increasing molecular mass.
5. Chemical properties are similar due to the presence of the same functional group.

Example: The Alkanes

The alkanes form a homologous series with the general formula CnH2n+2.

The first few members are:
Methane (CH4) – n=1
Ethane (C2H6) – n=2
Propane (C3H8) – n=3
Butane (C4H10) – n=4

Observation:
* All are hydrocarbons with only single bonds.
* Each successive member differs from the previous one by a -CH2- group.
* Ethane (C2H6) – Methane (CH4) = CH2
* Propane (C3H8) – Ethane (C2H6) = CH2
* Butane (C4H10) – Propane (C3H8) = CH2
* They all undergo similar chemical reactions, primarily combustion and substitution reactions.
* Their physical properties change gradually. For example, boiling points increase as the molecular size increases.

Question:

The question is about the unique properties of the element carbon that allow it to form a vast diversity of compounds. The key concepts are the ability of carbon atoms to bond with each other and with other elements. Specifically, you need to recall the types of covalent bonds carbon can form and the special nature of these bonds.


The huge number of carbon compounds is primarily due to two exceptional properties of carbon:

1. Catenation: This is the ability of an atom to form long chains or rings by bonding with atoms of the same element. Carbon exhibits a very strong tendency for catenation. Carbon atoms can bond with other carbon atoms to form single, double, or triple bonds, creating chains of varying lengths and structures, as well as closed rings.

2. Valency and Tetravalency: Carbon has a valency of 4, meaning it can form four covalent bonds. This tetravalency allows a carbon atom to bond with up to four other atoms, including other carbon atoms and atoms of different elements like hydrogen, oxygen, nitrogen, halogens, etc. This ability to form multiple bonds with diverse elements, coupled with catenation, results in an immense variety of molecular structures.

Together, these two properties—catenation and tetravalency—enable carbon to form an incredibly large and diverse array of organic compounds, which are the basis of life and many materials we encounter daily.

Question:

Combustion, fuels, oxidizing agents, flame temperature, efficiency of combustion.


When a fuel is burnt, it reacts with an oxidizing agent to produce heat and light. In welding, a very high temperature flame is required. Ethyne (C2H2) is a highly combustible fuel. Air contains approximately 21% oxygen, with the remaining being mostly nitrogen. Oxygen (O2) is a much more efficient oxidizing agent than air.

When ethyne is burnt with pure oxygen, the reaction is:
2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(g) + Heat

This reaction is highly exothermic and produces a very high flame temperature (around 3200°C) which is ideal for welding.

When ethyne is burnt with air, the reaction is much less efficient because of the presence of inert nitrogen. The combustion is incomplete, and a significant amount of heat is absorbed by the nitrogen in the air, which does not participate in the combustion.
C2H2(g) + 2.5O2(g) → 2CO2(g) + H2O(g) + Heat (from oxygen reacting with ethyne)
However, the large amount of nitrogen in the air absorbs heat and cools the flame. The flame temperature produced by burning ethyne with air is significantly lower (around 2300°C) than when burnt with pure oxygen. This lower temperature is insufficient for effective welding of most metals.

Therefore, a mixture of oxygen and ethyne is used for welding to achieve the high temperatures required for the process.

Question:

Surface tension, adhesion, cohesion, emulsification, mechanical agitation, force.


Agitation is necessary to get clean clothes because it helps to overcome the forces that hold dirt and grime to the fabric. Soap molecules have a dual nature: one end is attracted to water (hydrophilic) and the other end is attracted to oil and grease (hydrophobic). When soap is mixed with water, it reduces the surface tension of the water, allowing it to penetrate the fabric more easily. The hydrophobic ends of the soap molecules attach to the dirt and grease particles. Mechanical agitation, whether by beating, scrubbing, or a washing machine, provides the force needed to dislodge these dirt particles from the fabric. The agitation breaks up larger dirt particles into smaller ones and helps to lift them away from the fibers. The soap molecules then surround these lifted dirt particles, forming small structures called micelles, where the hydrophobic ends are inside, trapping the dirt, and the hydrophilic ends are outside, facing the water. This process is called emulsification. Without agitation, the soap would not be able to effectively detach the dirt from the clothes and suspend it in the water for rinsing away. Essentially, agitation provides the mechanical energy required to break the bonds between dirt and fabric and to facilitate the emulsification process by the soap.

Question:

Amphipathic nature of soap molecules, hydrophobic and hydrophilic interactions, role of solvent polarity, solubility.


Soap molecules are amphipathic, meaning they have a dual nature. They possess a long hydrocarbon tail, which is hydrophobic (water-repelling), and a polar head group, which is hydrophilic (water-attracting). When soap is added to water, a polar solvent, the hydrophobic tails try to escape the unfavorable contact with water. To minimize this contact, the soap molecules arrange themselves into spherical structures called micelles. In a micelle, the hydrophobic tails cluster together in the interior, shielded from the water, while the hydrophilic heads face outwards, interacting with the surrounding water molecules. This arrangement is energetically favorable in water.

In solvents like ethanol, which are less polar than water but still have some polar character, micelle formation is less likely to occur in the same way. Ethanol can solvate both the hydrophobic and hydrophilic parts of the soap molecule to some extent, reducing the driving force for the formation of distinct micellar structures. While some aggregation might occur depending on the concentration and specific soap, a well-defined micelle structure as seen in water is not typically formed in ethanol due to the different solubility characteristics and intermolecular interactions.

Question:

Hard water contains dissolved mineral salts, primarily calcium and magnesium ions. Soap is typically a sodium or potassium salt of a long-chain fatty acid. The reaction between these ions and soap molecules forms insoluble precipitates.


When hard water is treated with soap, the calcium (Ca²⁺) and magnesium (Mg²⁺) ions present in the hard water react with the soap molecules. Soap molecules are usually sodium or potassium salts of fatty acids, such as sodium stearate (C₁₇H₃₅COONa).

The reaction proceeds as follows:
1. The soap molecules dissociate in water to form fatty acid anions (e.g., stearate ions, C₁₇H₃₅COO⁻) and sodium ions (Na⁺).
C₁₇H₃₅COONa(aq) → C₁₇H₃₅COO⁻(aq) + Na⁺(aq)

2. The dissolved calcium and magnesium ions from the hard water then react with the fatty acid anions to form insoluble calcium stearate and magnesium stearate.
2 C₁₇H₃₅COO⁻(aq) + Ca²⁺(aq) → (C₁₇H₃₅COO)₂Ca(s) (Calcium Stearate – insoluble)
2 C₁₇H₃₅COO⁻(aq) + Mg²⁺(aq) → (C₁₇H₃₅COO)₂Mg(s) (Magnesium Stearate – insoluble)

These insoluble precipitates are what we observe as scum. The formation of this scum means that the soap is being consumed in forming these precipitates rather than in lathering and cleaning. This is why hard water reduces the effectiveness of soap.

Question:

Hydrogenation is a chemical reaction where hydrogen is added to a molecule. This typically involves an unsaturated compound, meaning it has double or triple bonds, and a catalyst. The addition of hydrogen saturates the molecule, breaking the double or triple bonds and forming single bonds.


Hydrogenation is a chemical process that involves the addition of hydrogen (H₂) to a molecule. It is commonly used to convert unsaturated organic compounds, such as alkenes and alkynes (which contain carbon-carbon double or triple bonds), into saturated organic compounds, such as alkanes (which contain only carbon-carbon single bonds). This reaction usually requires the presence of a catalyst, such as nickel (Ni), platinum (Pt), or palladium (Pd), to facilitate the addition of hydrogen. The catalyst helps to weaken the bonds in the hydrogen molecule and the unsaturated molecule, allowing for the formation of new single bonds. For example, an alkene with a C=C double bond can be hydrogenated to form an alkane with a C-C single bond, with the hydrogen atoms adding across the double bond. This process is widely used in various industries, including the food industry (e.g., hardening of vegetable oils to produce margarine) and the petrochemical industry.

Question:

Oxidation and Reduction: Oxidation is the loss of electrons, gain of oxygen, or loss of hydrogen. Reduction is the gain of electrons, loss of oxygen, or gain of hydrogen.
Redox Reactions: Reactions where both oxidation and reduction occur simultaneously.
Oxidising Agent: A substance that causes oxidation in another substance and gets reduced itself.


An oxidising agent is a chemical species that has the ability to oxidise another substance. This means it causes another substance to lose electrons, gain oxygen, or lose hydrogen. In the process of causing oxidation, the oxidising agent itself undergoes reduction, meaning it gains electrons, loses oxygen, or gains hydrogen. Common examples of oxidising agents include oxygen ($O_2$), halogens like chlorine ($Cl_2$) and bromine ($Br_2$), and strong acids like nitric acid ($HNO_3$) and sulfuric acid ($H_2SO_4$). For instance, in the reaction between magnesium and oxygen ($2Mg + O_2 \rightarrow 2MgO$), oxygen is the oxidising agent because it causes magnesium to be oxidised (lose electrons to form $Mg^{2+}$ ions) while oxygen itself is reduced (gains electrons to form $O^{2-}$ ions).

Question:

Nomenclature of haloalkanes: Identify the parent alkane chain, locate and name the halogen substituent, and assign numbers to indicate the position of the halogen.


The given compound is $CH3−CH2−Br$.
1. Identify the parent alkane chain: The longest carbon chain contains two carbon atoms. A two-carbon alkane is called ethane.
2. Identify the substituent: There is a bromine atom attached to the carbon chain. Bromine, when acting as a substituent, is named “bromo”.
3. Determine the position of the substituent: We need to number the carbon chain. If we number from left to right, the bromine is on carbon 1. If we number from right to left, the bromine is also on carbon 1. Therefore, the position of the bromine is 1.
4. Combine the parts to name the compound: The name is formed by the position of the substituent, the name of the substituent, and the parent alkane name. So, it is 1-bromoethane.

Final Answer: The final answer is $\boxed{\text{1-bromoethane}}$.

Question:

Micelles, hydrophobic tails, hydrophilic heads, grease and oil solubility, water solubility


Soaps are salts of long-chain fatty acids. They have a unique molecular structure with two distinct parts: a long hydrocarbon chain (hydrophobic tail) and a carboxylate group (hydrophilic head). When soap is added to water containing grease or oil (which are non-polar and insoluble in water), the hydrophobic tails of the soap molecules dissolve in the grease, surrounding it. The hydrophilic heads, on the other hand, remain on the outside, in contact with the water. This arrangement forms spherical structures called micelles. In a micelle, the grease is trapped inside, shielded by the hydrophobic tails, while the outer surface is hydrophilic, allowing the entire micelle to be suspended and dispersed in water. When the water is agitated (e.g., by washing), these micelles are easily washed away, taking the dissolved grease with them, thus cleansing the surface.

Question:

Hard water contains dissolved minerals, primarily calcium and magnesium ions. Detergents react with these ions, consuming them and reducing their lathering ability. Soft water lacks these ions, allowing detergents to lather freely.


Yes, you can check if water is hard by using a detergent. When you add soap or detergent to water, it usually produces lather or foam. In hard water, the dissolved minerals like calcium and magnesium ions react with the soap or detergent molecules. This reaction forms an insoluble precipitate (scum) and consumes the soap/detergent, thus reducing its ability to form lather. In soft water, there are fewer or no such dissolved minerals, so the soap/detergent can readily form lather. Therefore, if you add a small amount of detergent to a sample of water and it produces abundant lather, the water is likely soft. If it produces very little lather, or no lather at all, the water is likely hard.

Question:

Acids turn blue litmus red. Bases turn red litmus blue. Litmus paper is an indicator. Soaps are generally alkaline.


When you test soap with red litmus paper, you will observe that the red litmus paper turns blue. When you test soap with blue litmus paper, there will be no change; the blue litmus paper will remain blue. This observation indicates that soap is alkaline in nature because alkaline substances turn red litmus paper blue.