Explore topic-wise InterviewSolutions in .

This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.

6001.

Explain the reactions of metals such as potassium (K), sodium (Na), magnesium (Mg), aluminium (Al), zinc (Zn), lead (Pb), iron (Fe), copper (Cu), silver (Ag) and gold (Au) with oxygen.

Answer»

Solution :Here, given different metals show different reactivity towards oxygen. Hence, they react with oxygen in different MANNER. For example, metals such as potassium and SODIUM are highly reactive. Hence, they catch fire when kept in an open air. Therefore, sodium and potassium metals are STORED in kerosene oil.At ordinary temperature, metals such as magnesium, aluminium, zinc and lead reacts with oxygen to form their oxides, which cover the metal surface as a protective thin layer. This protective OXIDE layer prevents the further oxidation of metal.Iron does not react with oxygen of air at ordinary temperature. Iron does not burn on HEATING but iron filings burn vigorously when sprinkled in the flame of burner. Copper reacts with oxygen of air on heating to form a black substance copper (II) oxide, which covers the metal surface.Silver and gold does not react with oxygen even at high temperature. Sodium is the most reactive metal amongst the given samples of metals. Magnesium is less reactive metal, which indicates that magnesium is less reactive than sodium.
Discussion
6002.

Explain the process of transportation of substances in phloem.

Answer»

Solution :Translocation, i.e., transportation of food in plants takes place through pholem. Sieve tubes with the help of ADJACENT companion cells in the phloem move the soluble food in the form of sucrose, aminoacids etc in both upward and downward directions. Live cells of phloem actively take up material like sucrose using energy from ATP. This increases the osmotic PRESSURE of the tissue causing water to move into it. This pressure moves the material in the phloem to tissues which have less pressure. According to the needs of the plants food from leaves to storage organs of roots, fruits and SEEDS and the GROWING regions or from stored parts such as roots or stem to the buds (in SPRING) which needs energy to grow is transported.
Discussion
6003.

Explain the process of translocation of food materials in plants.

Answer»

SOLUTION :The transport of soluble product of photosynthesis is CALLED translocation.
It OCCURS in the phloem.
The products of photosynthesis are transported from leaves to all parts of the PLANT body.
Translocation takes place in the sieve rubes with the help of companion cells.
Discussion
6004.

Describe the process of nutrition in Amoeba with the help of diagram.

Answer»

SOLUTION :Amoeba is an important protozoa found in fresh water. If feeds on microscopic plants and animals present in water. The mode of nutrition in amoeba is holozoic and the process of obtaining food by amoeba is called phagocytosis. The different processes involved in the nutrition of amoeba are :
i) Ingestion :
Ingestion is the process of taking food in the body. Amoeba is a unicellular animal, so it doesn.t have a mouth for ingestion of food. Amoeba ingests the food by encircling it by forming pseudopodia, when the food is completely encircled the food is engulfed in the form of a bag called food vacuole.
ii) Digestion : Digestion is the process of breaking the large and insoluble molecules in to SMALL and water soluble molecules. In amoeba several digestive enzymes react on the food present in the food vacuoles and break it down into simple and soluble molecular.
iii) Absorption :
The food digested by digestive enzyme is then obsorbed in the cytoplasm by the process of diffusion. While the undigested food remains in the food vacuole. If a large amount of food is obsorbed by amoeba, the exess is stored in the cytoplasm in the form of glycogen and lipids.
iv) ASSIMILATION :
During this step the food obsorbed by the cytoplasm is used to obtain ENERGY, growth and repair. This process of utilizing obsorbed food for obtaining energy, repair and growth is called assimilation.
v) Egestion :
When, a sufficient amount of undigested food gets collected in the food vacuole it is THROWN out of the body by rupturing cell membranes. The process of removal of undigested food from the body is called egestion.
Discussion
6005.

Explain the process of digestion in the small intestine of man. Digestion of food in small intestine :

Answer»

Solution :Digestion of food in small INTESTINE :
Small intestine is the site of complete digestion of proteins, carbohydrates and fats.
GLANDS present in the walls of small intestine SECRETE intestinal juice.
Enzymes in the intestinal juice convert proteins into amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.
Digested food is ABSORBED by the VILLI present in the walls of intestine.
Discussion
6006.

Explain the principle involved in the purification of red bauxite by Bayer's process.

Answer»

Solution :(i) Nature of IMPURITY present in red BAUXITE.
(II) Chemical COMPOSITION of the red bauxite and the impurison present in it.
(iii) Comparison of chemical behaviour of red bauxite and the impurity with acids and bases.
(iv) Separation technique that can be ADOPTED for removing the impurity based on the above chemical behavioure.
Discussion
6007.

Explain the pattern of Mendeleev's periodic table.

Answer»

Solution :After the rejection of Newlands. law of octaves, ATTEMPTS were made to SEARCH for a pattern that correlated the properties of elements with their atomic masses.
The main credit for classifying elements goes to Dmitri Ivanovich Mendeleev, a Russian chemist.
Mendeleev arranged the elements on the basis of their fundamental property like the atomic mass and also on the similarity in chemical properties.
When Mendeleev started his work on classification of elements, only 63 elements were known.
Mendeleev examined the relationship between the atomic masses of the elements and their physical and chemical properties.
Mendeleev concentrated on the compounds formed by the elements with hydrogen and oxygen, as hydrogen and oxygen were very reactive and formed compounds with most of the elements.
The formulae of the hydrides and oxides of the various elements were treated as one of the basic properties of an element for its classification.
Thereafter, Mendeleev took 63 cards and on ach card, he wrote down the properties of each element. He sorted out the elements with similar properties and pinned the cards together on a wall one after the other in a VERTICAL column.
Mendeleev observed that most of the elements accommodated in a periodic table and elements were arranged in the order of their increasing atomic masses.
Mendeleev also observed that there occurs RECURRENCE of elements with similar physical and chemical properties after certain regular intervals. On the basis of these similarities, Mendeleev proposed his periodic law.
Mendeleev.s periodic law : "The properties of elements are the periodic function of their atomic masses."
Mendeleev.s periodic table consists of vertical columns CALLED .groups. andhorizontal rows called .periods..
Discussion
6008.

Explain the outline of the modern periodic table.

Answer»

SOLUTION :In the modern periodic table, the elements are ARRANGED in the increasing order of atomic NUMBERS.
The atomic number of any element is equal to the number of protons in the nucleus. The number of protons in the nucleus is equal to the total number of electrons in the atom.
In the modern periodic table, elements having same number of valence electrons are placed in vertical columns called groups.
The vertical columns of elements in a periodic table are called groups.
The horizontal rows of elements in a periodic table are called periods.
The modern periodic table consists of 18 groups and 7 periods.
Electronic configuration of elements in a period : Period number indicate the value of .n or shell (orbit) number .n. is the number of the given shell starting from the nucleus.
The maximum number of electrons that can be accommodated in any shell is `2n^(2)`, where .n. is the number of the given shell.

Electronic configuration of elements in a group :
All the elements in any group of the periodic table have IDENTICAL outershell electronic configuration.
All the elements in a group have same number of electrons in their valence shell as well as they have similar properties.
The valence shell electronic configuration of ALKALI metals is ns which is shown below:
Discussion
6009.

Explain the nature of the following salts: (a) NaH_(2)PO_(2) (b) Na_(2)HPO_(3) (c) Na_(2)HPO_(4)

Answer»

Solution :(i) identification of parent acid from which the respective salts are FORMED
(ii) structures of the given salts
(iii) number of hydroxyl radical present in the respective acid
(IV) number of replaceable hydrogen in the respective acid
(v) identification of the negative radical(s) that can be formed from the given ACIDS
(vi) DETERMINATION of the number of replaceable hydrogen(s) present in the given salts based on the composition of the above negative radicals
(vii) relation between the number of replaceable hydrogen (s) present in the SALT and its nature
Discussion
6010.

Explain the Newlands' law of octaves.

Answer»

Solution :The attempts of Dobereiner encouraged other chemists to correlate the properties of elements with their ATOMIC masses.
In 1866, John Newlands, an English scientist, arranged the then known elements in the ORDER of increasing atomic masses.
He started with hydrogen, the element having the lowest atomic mass and ended at thorium which was the 56TH element.
Newlands found that EVERY eighth element had properties similar to the properties of the first element.
Newlands observe this analogy with the octaves found in musical scale and proposed the law of octaves which is given as below:
Law of octaves : "When elements are arranged in order of their increasing atomic masses, then the properties of every eighth element are similar to the properties of the first element."
A part of the original form of Newlands. octaves is given below in Table 2.

In Newlands. octaves, the propeties of lithium and sodium are same. Sodium is the eighth element after lithium. Similarly. beryllium and magnesium possess similar properties.
Discussion
6011.

Explain the nature of the covalent found using the bond formation in CH_(3)Cl.

Answer»

Solution :The atomic numbers of carbon, hydrogen and chlorine are 6, 1 and 17 respectively. Hence, their electronic configuration may be written as follows :

This indicates that, carbon REQUIRES 4 electrons to COMPLETE its octet, hydrogen requires 1 electron to complete its DUPLET and chlorine requires 1 electron to complete its octet.
Therefore, carbon shares its four electrons, one electron each with three hydrogen atoms and one electron with chlorine atom to form four covalent BONDS completing its octet.

Thus, carbon attains the stable electronic configuration of nearest NOBLE gas neon, hydrogen attains the electronic configuration of noble gas helium, while chlorine acquires the electronic configuration of noble gas argon.
In short, chloromethane forms three `C-H` and one C - Cl covalent bonds.
Discussion
6012.

Explain the nature of the covalent bond using the bond formation in CH_(3)Cl.

Answer»

Solution :`CH_(3)Cl` is chloromethane. It is made up of one carbon atom, three hydrogen atoms and one CHLORINE atom. Carbon atom has 4 outermost electrons, each hydrogen atom has 1 electron and chlorine has 7 outermost electrons. Carbon shares its FOUR outermost electrons with three hydrogen atoms and one chlorine atom to form `CH_(3)Cl` as FOLLOWS:

Each atom in `CH_(3)Cl` has a noble gas electron arrangement. Carbon attains the nearest noble gas CONFIGURATION of neaon, hydrogen acquires the configuration of HELIUM while chlorine achieves the configuration of argon. Chloromethane contains three C-H and one C-Cl covalent bonds.
Discussion
6013.

Explain the nature of resultant solution when 20 mL of 0.05 M NaOH is mixed with 10 mL of 0.1 N HCl solution at 25^(@)C. When 10 mL of this solution is diluted 100 times what is the change in pH ?

Answer»

Solution :(i) calculation of net `H^(+)` ions concentration in themixture
(ii) calculate of the DIFFERENCE of number of `H^(+) and OH^(-)` ions GENERATED from the given amount RESPECTIVE acid and base
(III) determination of the pH of the given mixture at `25^(@)C`
(iv) relation between the pH of the solution and its NATURE
(v) relation between the nature of the solution and the effect of dilution
Discussion
6014.

Explain the nature of the covalent bond using the bond formation in CH_2Cl

Answer»

SOLUTION :
The carbon ATOM will share 4 electrons and hydrogen of chlorine share one each to BECOME stable. In this WAY, C forms three covalent bonds with hydrogen atoms and one covalent BOND with chlorine atom.
Discussion
6015.

Explain the methods of i) Oxygen supply to the cells ii) Release of carbondioxide to the atmopshere from the cells during the process of transportation in humans.

Answer»

Solution : i) 97% of oxygen is taken in the form of oxyhaemoglobin by HEMOGLOBIN pigment present in RBC of the BLOOD from lungs to various PARTS and 3% of oxygen is transported in dissolved form in blood plasma. ii) As carbondioxide is more SOLUBLE in water than oxygen, it is mostly transported in the dissolved form in blood plasma.
Discussion
6016.

Explain the method of making alloys

Answer»

Solution : (a) By fusing the METALS together .E.g. BRASS is made by , melting zinc and copper .
(b)By compressing finely divided metals.E.g.Wood metal: an ALLOY of LEAD, tin, BISMUTH and cadmium powder is a fusible alloy
Discussion
6017.

How can ethanol be converted into ethanoic acid?

Answer»

Solution :OXIDATION of ethanol USING acidified potassium DICHROMATE gives ethanal in first step which on further oxidation by same OXIDISING agents gives ethanoic acid.
Discussion
6018.

Explain the metallurgy of iron.

Answer»

Solution : Iron is chiefly extracted from haematite ore `(Fe_(2)O_(3))`
(i) Concentration by Gravity Separation: The powdered ore is washed with a steam of water.As a result, the lighter sand particles and other impurities are washed away and the heavier ore particles settle down (II) Roasting and Calcination: The concentrated ore is strongly heated in a limited supply of air in a reverberatory furnace.As a result, moisture is driven out and SULPHUR, arsenic and phosphorus impurities are oxidized off
(iii) Smelting (in a Blast Furnace): The charge consisting of roasted ore, coke and limestone in the ratio 8: 4: is smelted in a blast furnace by introducing it through the cup arrangement at the top.There are three important areas in the furnace
a.The Lower Regions (combustion Zone) :
The temerature is at `15006(@)C` . In this regoins coke burns with oxygen to FORM `CO_(2)` when the charge comes in contact with a hot blast of air .
`C+ O_(2)underset(Delta)overset(1500^(@)C) to Co_(2) + ("heat")`
It is exothermic reaction since heata is liberated .

b.The Middle Regions ( Fusion Zone ) :
The temperature prevails at `100^(@)C` in this regions `Co_(2)` is reduced to Co .
`CO_(2)+ C underset(Delta) overset(1000^(@))to2CO-"Heat"`
Limestone decomposes to calcium oxide and `CO_(2)`
`CaCO_(3) underset(Delta)to CO_(2) - "Heat"`
These two reactions are endothermic due to absorption of heat . Calcium oxide combines with silica to form calcium silicate slag.
`CaO + SiO_(2)rightarrowCasiS_(3)`
c.The Upper Regions ( Reduction Zone ) : The temperature prevails at `400^(@)C`. Inthis regions carbon monoxide reduces ferric oxide to form a fairly pure spongy iron .
`Fe_(2)O_(3) + 3CO overset(400^(2)C)to 2Fe+ 3CO_(2)`
. THe molten iron is collected at the bottom of the furnance after removing the slag .
The iron this formed is called pig iron . It is remelted and cast into different moulds . This iorn is called cast iron .
Discussion
6019.

Explain the mechanism of the cleansing action of soaps and detergents.

Answer»

Solution :The cleansing action of soaps and detergents follows the same principle : Soaps and detergents consist of a large hydrocarbon TAILS with a negatively charged heads. The hydrocarbon tail is hydrophobic and negatively charged head is hydrophilic. In solution, water molecules (being POLAR) aqueous, SURROUND the ions and not the organic part of the molecule.
When a soap or detergent is dissolved in water, the molecules AGGREGATE together as clusters, called micelles. The tails stick inwards and the heads outwards.

Mechanism of cleansing action : The hydrocarbon tail attaches itself to oily dirt. When water is agitated,the oily dirt tends to loosen from the dirty surface and dissociates into fragments and other tails to stick to oil. The solution now contains small globules of oil surrounded by soap or detergent molecules. The negatively charged heads present in water prevent the small globules from coming togetherforming aggregates. Thus, the oily dirt is removed from the object.
Discussion
6020.

Explain the mechanism of rusting?

Answer»

Solution : Rust is chemically known as HYDRATED ferric oxide (it is formulated as `Fe_(2)O_(3), XH_(2) O`).Rusting results in the FORMATION of scaling reddish brown hydrated ferric oxide on the SURFACE of iron and iron containing MATERIALS.
Discussion
6021.

Explain the mechanism of electrolysis of molten sodium hyroxide

Answer»

Solution :Molten SODIUM hydroxide dissociates to give `NA^(+) and OH^(-)` ions. `Na^(+)` ions go towards cathode while `OH^(-)` ions go towards anode.
REACTION at anode : `4OH^(-) rarr 2H_(2)O + O_(2) + 4E^(-)`
Reaction at cathode : `4Na^(+) + 4e^(-) rarr 4Na`
Discussion
6022.

Explain the mechanism of cleansing action of soap.

Answer»

Solution :A soap molecule contains two chemically DISTINCT parts that interact differently with water. It has one polar end, which is a short head with a carboxylate group `(-COONa)` and one non-polar end having the long tail made of the hydrocarbon chain.
The polar end is hydrophilic (Water loving) is nature and this end is attracted towards water. The non-polar end is hydrophobic (Water HATING) in nature and it is attracted towards dirt or oil on the cloth, but not attracted towards water. Thus, the hydrophobic part of the soap molecule traps the dirt and the hydrophilic part makes the entire molecule SOLUBLE in water.
When a soap or detergent is dissolved in water, the molecules JOIN together as clusters called .miscelles.. Their long hydrocarbon chains attach themselves to the oil and dirt. The dirt is thus surrounded by the non-polar end of the soap molecules. The charged carboxylate end of the soap molecules makes the micelles soluble in water. Thus, the dirt is WASHED away with the soap.
Discussion
6023.

Explain the mechanism of cleaning action of soap.

Answer»

Solution :The cleaning action is characterized by a soap micelle. The ionic end of soap micelle dissolves in water and the other end dissolved in oily scum. Thus micelles are ABLE to clean because oily scums gather in the centre of micelles. This forms an emulsion in the water. The micelles stay in solution as a colloid and do not come TOGETHER to PRECIPITATE becuase of ion-ion repulsion. Thus, the dirt SUSPENDED in the micelles is also EASILY removed away and our clothes are cleaned.
Discussion
6024.

Explain the manufacture of soap.

Answer»

Solution :Manufacture of soap: Kettle Process
This is the oldest method. But, it is still widely USED in the SMALL scale preparation of soap.
There are mainly, two STEPS to be followed in this process.
i. SAPONIFICATION of oil: The oil, which is used in this process, is taken in an iron tank (kettle). The alkaline solution (10%) is added into the kettle, a little in excess. the mixture is boiled by passing steam through it. The oil gets hydrolysed after several hours of boiling. This process is called Saponification
ii. Salting out of soap: Common salt is then added to the boiling mixture. Soap is finally precipitated in the tank. After several hours the soap rises to the top of the liquid as a .curdy mass.. The neat soap is taken off from the top. It is then ALLOWED to cool down.
Discussion
6025.

Explain the meaning of malleable and ductile.

Answer»

SOLUTION :MALLEABLE. A substance is SAID to be malleable if it can be beaten into sheets. E.g. metals are malleable.
Ductile. A substance is said to be ductile if it can be DRAWN into WIRES e.g. the metals are ductile.
Discussion
6026.

Explain the irregularities (anomalies) of Mendeleev's periodic table.

Answer»

Solution :In Mendeleev.s periodic table, the elements are arranged in the increasing ORDER of atomic masses. But there are few instances where Mendeleev had to place an ELEMENT with a slightly higher atomic mass before an element with a slightly lower atomic mass. Hence, the sequence was inverted so that elements with similar properties could be grouped together. For example, cobalt (Co) (atomic mass 58.9 u) placed before nickel (Ni) (atomic mass 58.7 u). Similarly, tellurium (Te) with higher atomic mass has been placed before iodine (I) with lower atomic mass.
Mendeleev left some gaps in his periodic table for those elements which were not discovered at that time.
Instead of considering gaps as defects, Mendeleev boldly PREDICTED the existence of some elements which would be discovered in due course of time and would fill the gaps.
Mendeleev named these elements by prefixing a SANSKRIT word eka (one) to the name of preceding element in the same group For example.

The properties of eka-aluminium predicted by Mendeleev and the element gallium which was discovered LATER are listed in Table 4.
Discussion
6027.

Explain the given reactions with examples: (a) Combustion reaction (b) Oxidation reaction (c ) Substitution reaction

Answer»

Solution :(a) Combustion reaction: Carbon compounds burns in oxygen to PRODUCE carbon dioxide alongwith release of large AMOUNT of heat and light.
`CH_(4)+2O_(2) to CO_(2)+2H_(2)O+` Heat and light
(b) Oxidation reaction: Ethanol is oxidised to ethanoic acid in the presence of alkaline `KMnO_(4)` (OXIDISING agent) on heating.
`CH_(3)CH_(2)OH underset("Heat") overset("Alk. "KMnO_(4))to CH_(3)COOH`
(c ) Substitution reaction: In the presence of sunlight, chlorine replaces the hydrogen ATOM of hydrocarbons.
`CH_(4)+Cl_(2) overset(hv) to CH_(3)Cl+HCl`
Discussion
6028.

Explain the formation of sodium chloride (NaCl).

Answer»

Solution :The compounds formed by the transfer of electrons from a metal to a non-metal are known as ionic compounds or electrovalent compounds. Atomic number of sodium is 11. Sodium atom has one electron in its outermost SHELL (M-shell). Sodium atom loses the electron from its M-shell and forms sodium cation `(Na^+)`and acquires stable complete octet structure of noble GAS neon (NE).
`underset(2,8,1)(Na) to underset(2,8)(Na^+) + e^-`
Similarly, atomic number of chlorine is 17. Chlorine atom has seven electrons in its outermost shell (M-shell). Chlorine atom gains one e which is lost by sodium atom and forms chloride anion `(Cl^-)`and acquires stable complete octet structure of noble gas argon (Ar).
`underset(2,8,7)(Cl)+ e^(-) to underset(2,8,8)(Cl^-)`
Sodium cation `(Na^+) `and chloride anion `(Cl^-)`being oppositely charged attract each other and are held by strong electrostatic forces of attraction and exists as sodium chloride (NaCl).
Sodium chloride exists as a group of oppositely charged IONS.
Discussion
6029.

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

Answer»

SOLUTION :Soap does not give foam EASILY with hard water. Hard water contains calcium and MAGNESIUM salts. Soap first reacts with the calcium ions and magnesium ions to form insoluble precipitates of calcium and magnesium salts of fatty ACID.
`underset(("soap"))("Sodium strearate")+"Hard water" to underset(("scum"))("Calcium stearate")+"Magnesium stearate"`
Discussion
6030.

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

Answer»

Solution :When soap is ADDED in hard water, the calcium and magnesium ions CAUSE PRECIPITATION of soap and the precipitate formed is called SCUM.
Discussion
6031.

(i) Explain the formation of ionic compound CaO with electron dot structure. Atomic number of calcium and oxygen are 20 and 8 respectively. (ii) Name the constituent metals of bronze.

Answer»

SOLUTION :`CA to Ca^(2+)+2E^(-)`
`2,8,8,2,""2,8,8 `
`O+2e^(-)toO^(2-)`
`2.6""2.8`
`(Ca^(2+))
Discussion
6032.

Explain the formation of hydrogen molecule (H_(2)) by covalent bond.

Answer»

Solution :The ATOMIC NUMBER of hydrogen is 1, hence its electronic configuration is `{:(K),(1):}`.
Thus, hydrogen has one electron in its K shell.
It requires one more electron to fill the K shell.
So, two hydrogen atoms share their electrons to form a molecule of hydrogen, `H_(2)`.
As a result, each hydrogen atom to attain the electronic configuration of the nearest noble gas helium, which has two electrons in its K shell.
Here, these two valence electrons are DEPICTED by dots or crosses is shown as follows:

The SHARED pair of electrons forms a single covalent bond between the two hydrogen atoms. A single covalent bond is also represented by a short line between the two atoms, is shown as follows :
>
Discussion
6033.

Explain the formation of covalent bonds iu oxygen molecule (O_(2)).

Answer»

Solution :The atomic number of oxygen is 8, so its electronic configuration is `{:(K,L),(2,6):}`
Thus, oxygen has SIX electrons in its L SHELL.
Therefore, it needs two more electrons to fill the L shell.
HENCE, two atoms of oxygen share two electrons of L shell to form a molecule of oxygen `(O_(2))`.
As a result, each ATOM of oxygen attains the electronic configuration of their nearest noble gas neon (Ne), which has eight electrons in their L shell.
These four valence electrons are depicted by dots or crosses is shown as follows :
Discussion
6034.

Explain the formation of covalent bonds in water molecule (H_(2)O).

Answer»

Solution :Oxygen is a central atom in the molecule of water. The atomic number of oxygen is 8, so its electronic CONFIGURATION is `{:(K,L),(2,6):}`.
Thus, oxygen has six electrons in its L SHELL.
Therefore, it needs two more electrons to fill the L shell.
Oxygen shares two of its valence electrons with one electron each of K shell of two hydrogen atoms to form a molecule of water `(H_(2)O)`.
As a RESULT, oxygen atom of water attains the electronic configuration of its nearest noble gas neon (Ne), which has EIGHT electrons in its L shell, while hydrogen atom attains the electronic configuration of its nearest noble gas helium (He), which has two electrons in its K shell.
Here, these valence electrons are depicted by dots or CROSSES is shown as follows:
Discussion
6035.

Explain the formation of covalent bonds in nitrogen molecule (N_(2)).

Answer»

SOLUTION :The atomic NUMBER of nitrogen is 7, so its electronic configuration is `{:(K,L),(2,5):}`.
Thus, nitrogen has five electrons in its L shell.
Therefore, it needs three more electrons to fill the L shell.
Two ATOMS of nitrogen share three electrons of L shell to form a MOLECULE of nitrogen `(N_(2))`.
As a RESULT, each atom of nitrogen attains the electronic configuration of their nearest noble gas neon (Ne), which has eight electrons in their L shell
These six valence electrons are depicted by dots or crosses is shown as follows:
Discussion
6036.

Explain the formation of covalent bonds in methane molecule (CH_(4)).

Answer»

Solution :Carbon is a central atom in the molecule of methane. The ATOMIC number of carbon is 6, so its electronic CONFIGURATION is `{:(K,L),(2,4):}`.
Thus, carbon has four electrons in its L shell.
Therefore, it needs four more electrons to fill the L shell.
Carbon shares its four VALENCE electrons with one electron each of K shell of four hydrogen atoms to form a molecule of methane `(CH_(4))`.
As a result, carbon atom of methane ATTAINS the electronic configuration of its nearest noble gas neon (Ne), which has EIGHT electrons in its L shell, while hydrogen atom attains the electronic configuration of its nearest noble gas helium (He), which has two electrons in its K shell.
Here, these valence electrons are depicted by dots or crosses is shown as follows :
Discussion
6037.

Explain the formation of covalent bonds in ammonia molecule (NH_(3)).

Answer»

SOLUTION :Nitrogen is a central atom in the molecule of ammonia. The atomic number of nitrogen is 7, so its electronic configuration is `{:(K,L),(2,5):}`
Thus, nitrogen has five electrons in its L shell.
THEREFORE, it needs three more electrons to fill the L shell.
Nitrogen shares three of its valence electrons with one electron each of K shell of three hydrogen atoms to form a molecule of ammonia `(NH_(3))`.
As a result, nitrogen atom of ammonia attains the electronic configuration of its NEAREST noble gas NEON (Ne), which has eight electrons in its L shell, while hydrogen atom attains the electronic configuration of its nearest noble gas helium (He), which has two electrons in its K shell.
Here, these valence electrons are depicted by DOTS or crosses is shown as follows:
Discussion
6038.

Explain the formation of covalent bond in hydrogen molecule (H_(2)).

Answer»

Solution :The atomic number of hydrogen is 1, hence its electronic configuration is `{:(K),(1):}`.
Thus, hydrogen has one electron in its K shell.
It requires one more electron to fill the K shell.
So, TWO hydrogen atoms share their ELECTRONS to form a molecule of hydrogen, `H_(2)`.
As a result, each hydrogen atom to attain the electronic configuration of the NEAREST noble gas helium, which has two electrons in its K shell.
Here, these two valence electrons are depicted by dots or crosses is shown as follows:

The shared pair of electrons FORMS a single covalent bond between the two hydrogen atoms. A single covalent bond is also represented by a short LINE between the two atoms, is shown as follows :
Discussion
6039.

Explain the formation of covalent bond in chiorine molcule (Cl_(2)).

Answer»

Solution :The atomic number of CHLORINE is 17, hence its electronic configuration is represented as,
`{:(K,L,M),(2,8,7):}`
Thus, chlorine has seven electrons in its valence M SHELL.
It requires one more electron to fill the M shell.
So, TWO chlorine atoms share their one electron each of M shell to form a molecule of chlorine `(Cl_(2))`.
As a result, each chlorine atom attains the electronic configuration of the nearest noble GAS argon, which has eight electrons in its M shell.
These two valence electrons are depicted by dots or crosses is shown as follows :
Discussion
6040.

Explain the following terms with one example each : Rancidity

Answer»

Solution :Rancidity : Oil and FAT containing articles when KEPT for some time in the open, start giving bad smell and taste. We SAY that these articles have gone rancid. This phenomenon of reaction of atmospheric oxygen with oils and FATS is called rancidity. Rancidity can be prevented by FLUSHING oil and fat containing articles with nitrogen. As a simple measure, oils and fats, and foods containing oils and fats are kept in aritight containers.
Discussion
6041.

Explain the following terms with one example each : Corrosion

Answer»

SOLUTION :CORROSION : Metals are attacked by atmospheric oxygen, carbon dioxide and moisture and are converted into metal oxides and carbonates. This phenomenon is called corrosion. In the case of iron, corrosion is called rusting.
Green coating on copper and black coating on silver are examples of corrosion. Corrosion ruduces the strength of the metal. Thus, it causes damage to BODIES, bridges, RAILINGS, ships, ETC. Corrosion can be prevented by applying paints on metal articles.
Discussion
6042.

Explain the following terms with one example each. rancidity.

Answer»

SOLUTION :Rancidity - the slow OXIDATION of OILS and FATS resulting in emission of a FOUL smell.
Discussion
6043.

Explain the following terms with one example each. (a) Corrosion (b) Rancidity

Answer»

Solution :(a) CORROSION: It is a process of SLOW and gradual conversion of a metal into its undesirable compounds (sulphides, carbonates, oxides, etc.) by the ATTACK of air and moisture (water) present in the atmosphere.
For example, reddish brown coating on iron, black coating on silver and green coating on copper are some examples of corrosion of iron, silver and copper respectively. Corrosion of iron is known as rusting.
(b) Rancidity: When the food items are kept for a long period, the fats and oils present in them get oxidised and their smell and taste change. They become rancid and so the process is called rancidity.
For example, rancid (DECAYING) flavour or smell in OLD cooking oil.
Discussion
6044.

Explain the following terms with one example each . (a) Corrosion (b) Rancidity

Answer»

Solution :(a) Corrosion: The SLOW eating up of metals by the REACTION of some atmospheric gases like oxygen,carbon-dioxide or water vapour is known as corrosion .
E.g: The copper articles get coated with green colour which is due to the formation of basic copper carbonate .
(b) Rancidity : Rancidity may be DEFINED as the naturaloxidation of the oils andfats, which are present in food items , giving bad SMELL and taste .
E.g.: Food items, containing fats and oils, give bad smellwhen they exposed to AIR for a long time .
Discussion
6045.

Explain the following terms with one example each. corrosion.

Answer»

Solution :Corrosion is DEFINED as a process where materials, usually metals, deteriorate as a RESULT of a chemical reaction with air. moisture, chemicals, etc.
For example, IRON, in the presence of moisture, reacts with oxygen to form hydrated iron oxide.
`4Fe+3O_2+nH_2Oto2Fe_2O_3.H_2O`
Discussion
6046.

Explain the following terms with one example each. (a) Corrosion (b) Rancidity

Answer»

Solution :Corrosion is defined as a process where materials, usually metals, deterioate as a result of a chemical reaction with AIR, moisture, chemicals, etc
For example, iron, in the presence of moisture, reacts with oxygen to form hydrated iron oxide
`4Fe +3O_(2)+nH_(2)O rarr 2Fe_(2)O_(3). nH_(2)O`
Rancidity is the process of OXIDATION of fats oils that can be easily noticed by the change in taste and smell is known as rancidity
For EXAMPL, the taste and smell of butter changes when KEPT for long.
Discussion
6047.

Explain the following properties of carbon compounds with example : (a) Oxidation reaction (b) Addition reaction (c ) Substitution.

Answer»

Solution :(a) Oxidation reaction. All the carbon compounds on complete oxidation give carbondioxide. On controlled or incomplete oxidation we get different products (depending upon starting compounds).
`CH_(3)CH_(2)OH underset(K_(2)Cr_(2)O_(7))OVERSET("ACIDIFIED")rarr CH_(3)COOH`
(B) Addition reaction. Compounds of carbon, having double or triple bond show addition reactions.
`CH_(2) = CH_(2) + HCl rarr CH_(3) - CH_(2) - Cl`
`CH -= CH + 2HCl rarr CH_(3) - CHCl_(2)`
(c ) SUBSTITUTION reaction. Carbon compounds having single covalent bonds show substitutions reactions.
Discussion
6048.

Explain the following processess with the help of chemical reactions : (a) Esterification (b) Saponification (c ) Hydrogenation.

Answer»

Solution :(a) Esterification. It is the process in which a carboxylic acid reacts with an alcohol in the presence of some mineral acid to give ESTER and water.
Example : `underset("Ethanol")(CH_(3)CH_(2)OH) + underset("Ethanoic acid")(CH_(3)COOH) overset("Acid")rarr underset("Ethyl ethanoate")(CH_(3)CH_(2)OOC CH_(3)) + H_(2)O`
(b) saponification. It is the process used for forming soap. In this process an ester is heated with alkali (NaOH or KOH) to give sodium salt of carboxylic acid and alcohol. For example when ethyl\ ethanoate is boiled with a solution of sodium hydroxide, sodium ethanoate and ethanol are produced.
`underset("Ethylethanoate")(CH_(3)COOC_(2)H_(5)) + NaOH overset("Boiled")rarr underset("Sod.ethanoate")(CH_(3)COONa) + underset("Ethanol")(C_(2)H_(5)OH)`
(c ) Hydrogenation. it is a process involving addition of hydrogen. it changes unsaturated compounds to saturated compounds. It also CAUSES REDUCTION of many organic compounds.
`underset("Ethene")(CH_(2)) = CH_(2) + H_(2) overset(Ni)rarr underset("Ethane")(CH_(3) - CH_(3))`
`underset("Ethene")(CH) -= CH + 2H_(2) overset(Ni)rarr underset("Ethane")(CH_(3) - CH_(3))`
`underset("Ethanoic acid")(CH_(3)COOH) + H_(2) + H_(2) overset(Ni)rarr underset("Ethanol")(CH_(3)CH_(2))`
Discussion
6049.

Explain the following in terms of gain or loss of oxygen with two examples each : Reduction

Answer»

Solution :Reduction : ADDITION of HYDROGEN or REMOVAL of OXYGEN in a reaction is called reduction
Examples :
(i) `CuO+H_(2)toCu+H_(2)O`
Oxygen has been removed from CuO in the above reaction.
(ii) `H_(2)S+Cl_(2)to2HCl+S`
Hydrogen has been added to `Cl_(2)` in the above reaction.
Discussion
6050.

Explain the following in terms of gain or loss of oxygen with two examples each. reduction.

Answer»

SOLUTION :Reduction reaction-
It is defined as the addition of hydrogen or REMOVAL of oxygen.
1) `Cl_2+H_2overset("HEAT")toHCl`
In the above reaction (1), Hydrogen is added to chlorine to FORM hydrogen chloride. Thus, chlorine gas is getting reduced to form hydrochloric acid
2) `H_2S+Cl_2overset("Heat")to2HCl+S`
In example,(2) Hydrogen is added to chlorine by hydrogen sulphide, thereby reducing chlorine
Discussion