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6051.

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

Answer»

Solution :Oxidation : ADDITION of oxygen or removal of HYDROGEN in a reaction is called oxidation.
Examples :
(i) `2Cu+O_(2)to2CuO`
(II) `4Al+3O_(2)to2Al_(2)O_(3)`
Discussion
6052.

Explain the following in terms of gain or loss of oxygen with two examples each: (a ) Oxidation (b) Reduction

Answer»

SOLUTION :Oxidation : It is a REACTION in which atom or molecule GAINS oxygen or loses HYDROGEN
For example,
`C+O_(2)to CO_(2)`
`2Cu+O_(2) to 2CuO`
In above reactions, .C. and .Cu. undergo Oxidation.
Reduction : It is a reaction in which atom or molecule loses oxygen or gains hydrogen.
For example,
`CUO+H_(2) to Cu+H_(2)O`
`CO_(2)+H_(2) to CO+H_(2)O`
In above reactions, .CuO. and `CO_(2)` undergo reduction.
Discussion
6053.

Explain the following in terms of gain or loss of oxygen with two examples each: (a) Oxidation (b) Reduction.

Answer»

Solution :(a) Oxidation: It is defined as a process which involves gain of oxygen. For EXAMPLE,
(i) `underset("Megnesium")(2Mg(s))+underset("Oxygen")(O_(2)(g))rarrunderset("Magnesium oxide")(2MgO(s))`
Here, Mg has gained oxygen to FORM MgO. Hence, Mg has been oxidised to MgO.
(ii) `underset("Copper")(2CU(s))+underset("Oxygen")(O_(2)(g))overset("Heat")rarrunderset("Copper oxide")(2CuO(s))`
In this REACTION, CU has gained oxygen to form CuO. Thus, Cu is oxidised to copper oxide (CuO).
(b) Reduction: It is defined as the process which involves loss of oxygen. For example,
(i) `underset("Copper oxide")(CuO)+underset("Hydrogen")(H_(2))overset("Heat")rarrunderset("Copper")(Cu)+underset("Water")(H_(2)O)`
In this reaction, copper oxide is losing oxygen. So, it is being reduced to copper.
(ii) `underset("Zinc oxide")(ZnO)+underset("Carbon")(C)overset("Heat")rarrunderset("Zinc")(Zn)+underset("Carbon monoxide")(CO)`
In this reaction, zinc oxide is losing oxygen. So it is being reduced to zinc.
Discussion
6054.

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

Answer»

Solution :Oxidation reaction-
It is a chemical reaction in which GAIN of oxygen or LOSS of hydrogen takes place.(1) `2MG(s)+O_2(g)OVERSET("Heat")to2MgO(s)`
Here Magnesium is oxidised to BECOME Magnesium Oxide.
(2) `2Cu(s)+O_2(g)overset("Heat")to2CuO(s)`
Discussion
6055.

Explain the following in terms of gain or loss of oxygen with two examples each . (a) Oxidation (b) Reduction

Answer»

Solution :Oxidation REACTION : It is a chemical reaction in which gain of oxygen or loss of hydrogen takes place ,br> (1) `2Mg(s)+O_(2)(g) OVERSET("heat") to 2MgO(s)`
Here, MAGNESIUM is oxidised to become Magnesium OXIDE.
(2) `2Cu(s)+O_(2)(g) overset("heat") to 2CuO(s)`
Here, copper is oxidised to become copper oxide.
Reduction reaction : It is chemical reaction in which loss of oxygen or gain of hydrogen takes place.
(1) `CuO+H_(2) overset("Heat") to Cu+H_(2)O`
here, copper oxide is reduced to become copper.
`ZnO+C overset("Heat") to Zn +CO`, here zinc oxide is reduced to become Zinc.
Discussion
6056.

Explain the following : (i) Most metal oxides are insoluble in water but some of these dissolve in water, what are these oxides and their solutions in water called? (ii) At ordinary temperature, the surface of metals such as magnesium, aluminiumand zinc etc, is covered with a thin layer. What is the composition of this layer? State its importance. (iii) Some alkali metals can be cut with a knife.

Answer»

Solution :(i) These OXIDES are called basic oxides and their solutions in water are called ALKALIS.
(ii) This layer formed is protective oxide layer which PREVENTS the metals from further oxidation.
(iii) Some alkali can be CUT with a knife because they are very soft and have LOW densities.
Discussion
6057.

Explain the following: (i) CH_(3)COOH is a weak acid (ii) Propene undergoes addition reaction (iii) The gas stoves have inlets for air.

Answer»

Solution :(i) DUE to the incomplete ionization of acetic `(CH_(3)COOH)` acid
(ii) `CH_(3) - CH = CH_(2)` UNDERGOES addition REACTION because of double bond.
(iii) Sufficient supply of `O_(2)` for complete combustion.
Discussion
6058.

Explain the flow of energy and harmful chemicals in an ecosystem.

Answer»

Solution :FLOW of energy is unidirectional. The energy that is CAPTURED by the AUTOTROPHS does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs. As it moves progressively through the various trophic levels it is no longer available to the previous level. The energy available at each trophic level gets diminished progressively due to loss of energy at each level. In the same way the harmful chemicals ENTER our bodies through the food chain. As there chemicals are not degradable they get accumulated progressively at each trophic level. As human beings occupy the TOP level in any food chain the maximum concentration of these chemicals get accumulated in our bodies. this phenomenon is known as biological magnification
Discussion
6059.

Explain the factors influencing the rate of a reaction.

Answer»

Solution :The factor influencing the RATE of a reation are,
(i)Nature of the reactions:The reaction of sodium with hydrochloric acid is faster than that with acetic acid .Do you know why?Hydrochloric acid is a stronger acid than acetic acid and thus more reactive.So,the nature of the reactants influence the reaction rate.
`2Na_((s))+2HCl_((aq))+H_(2(g))(FAST)`
`2Na_((s))+2CH_(3)COOH_((aq))to2CH_(3)COONA_((aq))+H_(2(g))(slow)`
(ii)Concentration of the reactants:Changing the amount of the reactants also increases the reaction rate.the amount of the substance present in a certain volume of the solution is called.concentration..More the concentration ,more particles per volume exist in it and hence faster the reaction.Granulated zinc reacts faster with 2M hydrochloric acid than 1M hydrochloric acid.
(iii)Temperaure:Most of the reactions go faster at higher temprature.Because adding heat to the reactants provides energy to break more bonds and thus speed up the reaction.Calcium carbonatereacts slowly with hydrochloric acid at room temprature.When the reaction mixture is heated the reaction rate increases.
(iv)Pressure:If the reactants are gases ,increasing their pressure increases the reaction rate.This is because ,on increasing the pressure the reacting particles COME closer and collide frequently .
(v) Catalyst:A catalyst is a substance WHIC increases the reactions rate without being cosumed in the reaction.In certain reactions adding a substancce as catalyst speeds up the reaction.For example,on hearting potassium chlorate,it decomposes into potassium chloride and oxygen gas ,but at a slower rate.If manganese dioxide is added ,it increase the reaction rate.
(vi)Surface area of the reactants:When solid reactants are involve in a reaction,their POWDERED form reacts more readily.For example,powedered calcium carbonate reacts more readily with surface are and more energy is availble on collision of the reactant particles thus,the reactions rate is increased you will study more about reaction rate in you higher classes.
Discussion
6060.

Explainthe factorsinflucencingthe rateof areaction

Answer»

Solution :Importantfactorsthataffectrateof a reactionarefollows :
(ii )The reactionof sodiumwithhydrochloricacidis fasterthanwith aceticacid.
(iii )Hydrochloricacidis strongerthan aceticacidand morereactive. sothenatureof THEREACTANTS influencereaction rate .
`2Na_((s))+2HCl_((AQ)) toH_(2(g))` Fast
`2Na_((s))+2CH_(3)COOH_((aq)) to2 CH_(3)COONa_((aq))+ H_(2(g))("slow")`
Concentrationof thereactants:
changingtheamountof thereactantsalsoincreases thereactionrate. Theamountof the substance presentin acertainvolumeof thesolutionis called'concentration '.Morethe concentration, moreparticlesreaction , Granulatedzincreactsfasterwith2M hydrochloricacidthan1Mhydrochloricacid .
Temperature:
Increaseintemperatureprovidesenergytobreakmorebondsandthusspeedup thereaction, E.g`CaCO^3`reacts slowlywithup thereact slowlywith HCIat roomtemperature. WHenthe reactionmixutreisheatedthe reactionrateincreases.
PRessure :
(i)ifthereactantsare gases ,increasingtheirpressure, increasesthereactionrate .
sinceonincreasingpressurethe reactingparticlescomecloserandcollidefrequently .
Catalyst:
(i)A catalystincreasereactionratewithoutbeingconsumed in thereaction.
(ii )in certainreactions , adding a substanceascatalystspeedsup thereaction.
Surface areaof thereactants :
Powdering of thereactants, increasingthesurfaceareaand moreenergyis availableon collisionof reactant particles, thusthereaction rateis increased.
Discussion
6061.

Explain the extraction of reactive metals.

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SOLUTION :Highly reactive metals cannot be extracted from their compounds by heating with carbon as it does not reduce the oxides of sodium, magnesium, CALCIUM, aluminium, ETC. to the RESPECTIVE metals. These metals are OBTAINED by the electrolysis of their molten chloride. The metals are depoited at the cathode and chloride is liberated at the anode.
At cathode : `Na^(+)+e^(-)toNa`
At anode : `2Cl^(-)toCl_(2)+2e^(-)`
Discussion
6062.

Explain the extraction of metals towards the top of the activity series.

Answer»

Solution :The metals like sodium, potassium, magnesium, CALCIUM etc. are placed high up in the reactivity series cannot be reduced by heating with carbon. These metals have more affinity for oxygen so these can be obtained by electrolysis of their molten chlorides. The metals GET deposited on the cathode and the chlorine is liberated at the anode.
At Cathode : `NA^(+)+e^(-)toNa`
At anode : `2Cl^(-)toCl_(2)+2e^(-)`
Aluminium can be obtained by the electrolysis of aluminium OXIDE.
Discussion
6063.

Explain the extraction of metals remain at the top of the reactivity series.

Answer»

Solution :The metals at the top of the reactivity series are HIGHLY reactive. They cannot be obtained from their compounds by heating with carbon, because these metals have more affinity for oxygen than carbon. Hence, for the extraction of such metals electrolytic reduction method is used.For example, sodium, MAGNESIUM and calcium are obtained by the electrolysis of their molten chlorides. During electrolysis, the metals are deposited at the cathode (the NEGATIVELY charged electrode). while chlorine is liberated at the anode (the positively charged electrode) in the electrolytic CELL. For example, At cathode (-): `Na^(+) + e^(-) to Na(s)`
At anode (+) : `2Cl^(-) to Cl_2(g) + 2e^(-)`
Similarly, aluminium is obtained by the electrolytic reduction of aluminium OXIDE.
Discussion
6064.

Explain the extraction of metals low in the reactivity series.

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SOLUTION :Metals low in the reactivity SERIES are very UNREACTIVE. The oxides of these metals can be reduced to metals by heating alone.For example, Cinnabar (HgS) is an ore of mercury. When it is heated in air, it is first converted into mercuric oxide (HgO) then, mercuric oxide is reduced to mercury (HG) on further heating.
`2HgS(s) + 3O_2(g) overset("HEAT")(to) 2HgO(s) + 2SO_2 (g)`
`2HgO(s) overset("heat")(to) 2Hg(l) + O_2(g)`
Thus, mercury is separated.
Similarly, copper which is found as `Cu_2S`in nature can be obtained from its ore by heating in air. Here, `Cu_2S`is reduced to Cu.
`2Cu_2S(s) + 3O_2(g) overset("heat")(to) 2Cu_2O(s) + 2SO_2(g)`
`2Cu_2O(s) + Cu_2S(s) overset("heat")(to) 6Cu(s) + SO_2(g)`
Discussion
6065.

Explain the extraction of metals low in activity series.

Answer»

Solution :Metals placed low in the activity series are not very active. The oxides of these metals can be EASILY reduced to metals by heating only. When the sulphide ores of these metals are heated in air, these GET converted into oxides. On further heating metal oxides can be reduced to metals.
(a) MERCURY (Hg)
`2HgS+3O_(2)(G)overset("Heat")to2HgO(s)+2SO_(2)(g)`
`2HgO(s)overset("Heat")to2Hg(1)+O_(2)(g)`
(b) COPPER (Cu)
`2Cu_(2)S+3O_(2)(g)overset("Heat")to2Cu_(2)O(s)+2SO_(2)(g)`
`2Cu_(2)O+Cu_(2)Soverset("Heat")to6Cu(s)+SO_(2)(g)`
Discussion
6066.

Explain the extraction of metals in the middle of activity series.

Answer»

Solution :The metals placed in the middle of activity series are moderately reactive and then often are present in NATURE are sulphides or carbonates. Iron, zinc, lead, copper, etc. are the examples of there metals. These metal sulphides are converted into metal oxides by heating strongly in the presence of excess air. This process is roasting. The carbonate ores are heated strongly in the presence of limited air and it is called calcination.
Roasting : `2ZnS(s)+3O_(2)(g)overset("Heat")to2ZnO(s)+2SO_(2)(g)`
Calcination : `ZnCO_(3)(s)overset("Heat")toZnO(s)+CO_(2)(g)`
The metal oxides are reduced by carbon like reducing agents.
`ZnO(s)+C(s)toZn(s)+CO(g)`
The HIGHLY reactive metals like Na, Ca, Al, etc. are also USED to reduce some metals because they displace metals of lower reactivity from their compounds. For example : `3MnO_(2)(s)+4Al(s)to3Mn(1)+2Al_(2)O_(3)(s)+"Heat"`
`Fe_(2)O_(3)(s)+3Al(s)to2Fe(1)+Al_(2)O_(3)(s)+"Heat"`
Discussion
6067.

Explain the extraction of metals in the middle of the reactivity series.

Answer»

Solution :The metals in the middle of the reactivity series such as iron, lead, zinc, copper are moderately reactive. These metals are usually present as sulphides or carbonates ore in nature. It is easier to obtain a metal from its oxide as compared to its sulphides and carbonates. Therefore, prior to reduction, the metal sulphides and carbonates are CONVERTED into metal oxides. The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is called roasting. The carbonate ores are changed into oxides by heating strongly in limited air. This process is called calcination.The CHEMICAL reactions that take place during roasting and calcination of zinc ores are as follows: Roasting:
`2ZnS(s) + 3O_2(g) overset("heat")(to) 2ZnO(s) + 2SO_2(g) `
Calcination :`ZnCO_3(s) overset("heat")(to) ZnO(s) + CO_2(g)`
The metal oxides are then reduced to the corresponding metals by heating with reducing agent like carbon.
`ZnO(s) + C(s) overset("heat")(to) Zn(s) + CO(g)`
Besides using carbon, the highly reactive metals such as SODIUM, calcium, ALUMINIUM, etc. are used as reducing agent, because they can displace metals of lower reactivity from their compounds. For example, when manganese dioxide is heated with aluminium powder, it is reduced to MN as follows:
`3MnO_2 (s) + 4Al (s) to 3Mn(l) + 2Al_2O_3(s) + `heat
Discussion
6068.

Explain the extraction of copper from copper pyrites.

Answer»

Solution : Extraction of copper from copper PYRITES invovles the following steps :
(i) Concentration of are : The ore is crushed and the concentrated by forth floatation process
(ii) Roasting : The Concentrated ore is roasted in excess of air . During the process of roasting , the moisture and volatile impurities are removed . Sulphur , Phosphorus , arsenic and antimony are remoed as oxides , copper pyrite is partly converted into suphide of copper and iron . `2CuFeS_(2)+ O_(2)rightarrowCu_(2)S+2FeS+ SO_(2)uparrow`
SMELTING: The roasted ore is mixed with powdered coke and SAND and is heated in a blast fumace to obtain matte (Cu, S + FeS) and slag.The slag is removed as waste.(iv) Bessemerisation: The molten matte is transferred to Bessemer converter in order to obtain blister copper.Ferrous sulphide from matte is oxidized to ferrous oxide, which is removed as slag using silica .
`2FeS+ 3O_(2)rightarrow2FeO+2SO_(2)uparrow`
`FeO+SiO_(2)rightarrowFeSiO_(3)` (slag)
`2Cu_(2)S+3O_(2)rightarrow2Cu_(2)O+ 2SO_(2)upaarow`
`2Cu_(2)O+Cu_(2)Srightarrow6 Cu + So_(2)uparrow`
(V)Refining : Blister copper contians 98% of pure copperr and 2% of impurities ans is purified by electrolytic refinig ,. This method is sused to get metala of a high degree of purity . For eletrolytic refining of copper , we use :
Cathode: A thin plate of pure copper metal.
ANODE: A block of impure copper metal.
Electrolyte: Copper sulphate solution acidified with sulphuric acid.When electric current is passed through the electrolytic solution, pure copper gets deposited at the cathode and the impurities settle at the bottom of the anode in the form of sludge called anode mud.
Discussion
6069.

Explain the experiment conducted by Newton to show that white light contains seven colours. Sun appears red in colour during sunrise but appears white at noon. Explain with the reasons.

Answer»

Solution :(i) Newton allowed white light from the Sun to enter a dark room through a small APERTURE and placed the glass prism in the path of light RAYS.
The light coming from the prism was received on white screen.
On the screen a coloured patch like a rainbow was found which was termed as spectrum.
The spectrum was found to be made of seven COLOURS VIBGYOR.
From the above EXPERIMENT, Newton concluded that white light consists of seven colours.
(i) At the lime of sunrise when the sun is near the horizon, the sunlight has to travel the larger distance through the atmosphere to REACH us. During this long journey of sunlight, most of the shorter wavelength blue-colour present in it is scattered out and away from our line of sight. So, the light reaching us at the lime of sunrise consists mainly of longer wavelength red colour due to which it appears to be red.
(iii) At noon sun is overhead and light rays travel comparatively for smaller distance and only little ofblue/ violet light scatter, so sun appears white.
Discussion
6070.

Explain the electronic configuration of noble gases (He, Ne, Ar) , metals (Na, Mg, Al, K , Ca) and non metals (N,O,F,P,SCl)

Answer»

SOLUTION :
Discussion
6071.

Explain the electrometallurgical process for the extration of potassium using fused potassium chloride

Answer»

Solution :ELECTROLYTE : Fused potassium chloride
Cathode : IRON
Anode: Graphite (INERT anode)
Dissociation of electroyte : `KCl RARR K^(+) + CL^(-)`
Reactions at the cathode : `K^(+) + e^(-) rarr K`
Reactions at the anode: `[Cl^(-) - e^(-) rarr Cl^(-)] xx 2`
`Cl + Cl rarr Cl_(2)`
Discussion
6072.

Explain the electrolyte refining of copper .

Answer»

SOLUTION : Cathode,A thin PLATE of pure copper metal.
Electrolyte . Copper sulphate solution + dilute `H_(2)SO_(4)`
When electric current is passed through the electrolytic solution, pure copper gets DEPOSITED at the cathode and the IMPURITIES are SETTLED at the bottom as anode mud .
Discussion
6073.

Explain the effect of soap in cleansing action.

Answer»

Solution :The molecules of soap are sodium or potassium salts of long chain carboxylic acids.
Two ends of soap molecule possess different properties. One end is hydrophilic and it dissolves in water, while the other end is HYDROPHOBIC and it dissolves in hydrocarbons.
When soap is at the surface of water, the hydrophobic tail of soap will not be soluble in water and the soap will ALIGN along the surface of water with the ionic end in water and the hydrocarbon .tail protruding out of water.

Inside water, these molecules have a particular orientation that KEEPS the hydrocarbon portion out of the water.
This happens due to the formation of clusters of molecules in which the hydrophobic tails are in the interior part of the cluster and the ionic ends are on the surface of the cluster.
This formation is called a micelle.
Soap in the form of a micelle collects the oily dirt in the centre of it and is able to CLEAN.
These micelles exist in solution as a colloid.
Micelles do not cluster to precipitate because of ion-ion repulsion.
Thus, the dirt suspended in the micelles is also easily rinsed AWAY.
The soap micelles are large enough to scatter light, hence a soap solution appears cloudy.
Discussion
6074.

Explain the effect of change in temperature on the conductivity of the following conductors. Justify with appropriate reasons

Answer»

Solution :(i) Mechanism of conduction of electricity in the given conductors.
(ii) Requisite for a solid SUBSTANCE to conduct electricity
(iii) Type of BOND present in metal
(vi) Change that take place in the MOVEMENT of the constituent particles of metal due to the change in tempeature.
(iv) Particles that conduct electricity in an electrolyte.
(v) Comparison of number of ions present in equimolar `CuSO_(4)` solution and acetic acid solution.
(vi) Effect of change of TEMPERATURE on the concentration of ions in the above solutions.
(vii) Relation between conductivity of an electrolyte and the concecntration of ions in it
Discussion
6075.

Explain the effect of addition of CO and O_(2) and solid carbon to the equilibriummixture separately. Also explain the effect of addition of all the three simultaneously . What happensto the equilibrium when the above changes are carried out in a container having less volume ?

Answer»

Solution :(i) EFFECT of addition of product or reactant at constant volume at equilibrium
(ii) effect of addition of product or reactant at constant volume at equilibrium
(iii) effect of addition of solidreactant
(iv) RELATION between volume adn pressure of the system. Effect of addition of addition of COMPONENTS on equilibrium at LESSER volume.
Discussion
6076.

Explain the difference between endothermic and exothermic reactions with examples.

Answer»

SOLUTION :
Discussion
6077.

Explain the contribution of Mendeleev in the classification of elements.

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
6078.

Explain the combustion zone in the extraction of iron from its ore ? Write the chemical reaction occurringin that zone .

Answer»

SOLUTION :The LOWER Region ( Combustion Zone ) - The temperatureis at `1500^(@)C`, In this region , cokeburns with oxygen to form `CO_2` when the CHARGE comesin contact with a hot BLAST of air .
`C+O_2underset(Delta )overset(1500^(@)C) to CO_2+`heat
It is an exothermicreaction since heat is liberated .
Discussion
6079.

Explain the cleansing action of soap.

Answer»

SOLUTION :A soap molecule has two parts : a HYDROCARBON and the `COO^(-)Na^(+)` group. The hydrocarbon part as hydrophobic and gets ATTACHED to dirt and grease, this part is water repelling. The `COO^(-)Na^(+)` part is hydrophilic and gets attached to water molecules. Thus, the dirt and grease attached to hydrophobic part of soap molecules get washed away becase the hydrophilic molcules `(COO^(-)Na^(+))` group makes the ENTIRE clump, FORMED by soap molecules and dirt, soluble.
Discussion
6080.

Explain the classification of organic compounds.

Answer»

SOLUTION :
Discussion
6081.

Explain the classification of molecules based on atomicity.

Answer»

Solution :In accordance with the NUMBER of atoms present in the moleculas, they are classified as mono atomic, diatomic, triatomic and POLYATOMIC MOLECULES showing that they contain one, two, THREE or more than 3 atoms RESPECTIVELY.
Discussion
6082.

Explain the classification of hydrocarbon compounds based on their structures.

Answer»

Solution :Hydrocarbon compounds are classified on the basis of the arrangement of carbon atoms (ACCORDING to structure) into following three categories :

(a) Straight chain compounds : Hydrocarbon compounds in which all carbon atoms are arranged in straight chain (linearly) are called straight chain compounds.
For example,
Propane `(C_(3)H_(8)):H-underset(H)underset(|)overset(H)overset(|)C-underset(H)underset(|)overset(H)overset(|)C-underset(H)underset(|)overset(H)overset(|)C-H`
Pentane `(C_(5)H_(12)):H-underset(H)underset(|)overset(H)overset(|)C-underset(H)underset(|)overset(H)overset(|)C-underset(H)underset(|)overset(H)overset(|)C-underset(H)underset(|)overset(H)overset(|)C-underset(H)underset(|)overset(H)overset(|)C-H`
(b) Branched chain compounds : Hydrocarbon compounds in which carbon atoms are arranged in straight chain, as well as possess one or more branches are called branched chain compounds.
For example, carbon SKELETON. of four carbon atoms of butane can be arranged in two different possible skeletons as follows :
(1) `C-C-C-C`

Here, satisfying the remaining valencies with hydrogen, gives following structures :

Two MOLECULAR structures for `C_(4)H_(10)`
For example, carbon .skeleton. of six carbon atoms of hexane `(C_(6)H_(14))` can be arranged in five different possible skeletons as follows :
(1) `C-C-C-C-C-C`
(2) `C-C-C-underset( C )underset(|)C-C`
(3) `C-C-underset( C )underset(|)C-C-C`
(4) `C-underset( C )underset(|)C-underset( C )underset(|)C-C`
(5) `C-C-underset( C )underset(|)overset( C )overset(|)C-C`
Here, satisfying the remaining valencies with hydrogen gives following structures :
(1) `CH_(3)-CH_(2)-CH_(2)-CH_(2)-CH_(2)-CH_(3)`
(2) `CH_(3)-CH_(2)-CH_(2)-underset(CH_(3))underset(|)(CH)-CH_(3)`
(3) `CH_(3)-CH_(2)-underset(CH_(3))underset(|)CH-CH_(2)-CH_(3)`
(4) `CH_(3)-underset(CH_(3))underset(|)CH-underset(CH_(3))underset(|)CH-CH_(3)`
(5)` CH_(3)-CH_(2)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)C-CH_(3)`
( c ) Ring structures OR Cyclic compounds : Hydrocarbon compounds in which the first carbon atom is DIRECTLY linked with the end (last) carbon atom, forming ring or cyclic structures are called ring structures or cyclic structures are called ring structures of cyclic compounds.
For example,
(1) Structure of cyclohexane :

(2) Structure of CYCLOPROPANE :
Discussion
6083.

Explain the classification (group) of metals on the basis of reactivity.

Answer»

Solution :On the basis of reactivity, metals are classified as follows: (1) Metals of low reactivity: The metals at the bottom of the reactivity series are least reactive. They are often found in free state. For example, GOLD, silver, PLATINUM and copper. Copper and silver are ALSO found in the combined state as their sulphide or oxide ORES. (2) Metals of medium reactivity: The metals 3 in the middle of the reactivity series are moderately reactive. For example, Zn, Fe, Pb. They are found in the earth.s crust mainly as oxides, sulphides or carbonates. (3) Metals of HIGH reactivity: The metals at the top of the reactivity series are highly reactive. For example, K, Na, Ca, Mg and Al. These metals are so reactive that they are never found in a free state.
Discussion
6084.

Explain the classification based on the direction of the reaction.

Answer»

Solution :Reversiblereactions :
(i)A reversiblereactionis a reactionthatcanbe REVERSED .
(ii )The productscan beconvertedbackthat canreactants .
(III )A reversiblereaction is representedbya doublearrowwiththeirheads in thedirectionoppositeto eachother .

(iv )The compound`'Ab'` undergoesdecomposition to formthe products'A' and'B'.
(v )it istheforwardreaction.
(vi)As soonas theproductsare formed, theycombinetogther totoform 'AB' . It is thebackwardreaction .
E.g `PCI_(5(g))hArrPCI_(3(g)) +Cl_(2(g))`
Irreversiblereactions :
(i)the reactionthatcannotbe reversediscalledirreversiblereaction .
(ii)E.gCombustionof coalintocarbondioxideand water.
`underset("Coal ") underset("Oxygen ")O_(2(g)) tounderset("Carbondioxide")CO_(2(g))+`Heat
(iii) Solidcoalburns - withoxygenand getsconverted intocarbondioxidegasand water.
(iv )As soonasthegasesformed, ESCAPES outofthe reactioncontainer .
(v)It ishardto decomposea gasintoa solid .
(vi )THus, thebackward reactionis notposibleinthiscase, soit isan irrversiblereaction .
Discussion
6085.

Explain the classification of alloys based on iron content .

Answer»

Solution :Based on the presence or absence of IRON , alloys can be classified into :
(i) FERROUS alloys :CONTAIN Iron as amajorcomponent .A few examplesof ferrousalloys are Stainless Steel , NickelSteel etc.
(ii) Non - ferrousalloys : These alloys do not contain Iron as a majorcomponent. For example , Aluminium ALLOY , COPPER alloy etc .
Discussion
6086.

Explain the chemical reactions of ethanoic acid.

Answer»

Solution :(1) Esterification reaction : Reaction of a carboxylic acid and an ALCOHOL in the presence of an acid catalyst forms ester and water. This reaction is called an esterification reaction.
Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to form ester and water.
`underset("Ethanoic acid")(CH_(3)-underset(O)underset(||)C-OH)+underset("Ethanol")(HO-CH_(2)-CH_(3))overset("Acid")iffunderset("Ethyl acetate (Ester)")(CH_(3)-underset(O)underset(||)C-O-CH_(2)CH_(3))+underset("Water")(H_(2)O)`
Esters are sweet smelling liquids and are used in making perfumes and flavouring agents.
A reaction of an ester with an alkali forming an alcohol and sodium salt of carboxylic acid is called saponification reaction.
On treating with sodium hydroxide, which is an alkali (base), the ester is converted back to alcohol and sodium salt of carboxylic acid.
`underset("Ethyl acetate")(CH_(3)COOC_(2)H_(5))overset(NaOH)tounderset("Ethanol")(C_(2)H_(5)OH)+underset("acetate")underset("Sodium")(CH_(3)COONa)`
(2) Reaction with a base (Neutralisation) :
LIKE mineral ACIDS `(HCI, HNO_(3), H_(2)SO_(4))`, carboxylic acid reacts with a base to form salt and water. This is called neutralisation reaction.
Ethanoic acid reacts with sodium hydroxide and forms sodium ethanoate (salt) and water.
`underset("Ethanoic acid")(CH_(3)-underset(O)underset(||)C-OH)+underset("hydroxide")underset("Sodium")(HO-Na)tounderset("Sodium ethanoate")(CH_(3)-underset(O)underset(||)C-ONa)+underset("Water")(H_(2)O)`

(3) Reaction with carbonates and hydrogen-carbonates : Ethanoic acid reacts with carbonates and hydrogencarbonates to form a salt, water and carbon dioxide.
Here, the salt formed is sodium acetate.
`underset("acid")underset("Ethanoic")(2CH_(3)COOH)+underset("carbonate")underset("Sodium")(Na_(2)CO_(3))tounderset("acetate")underset("Sodium")(2CH_(3)COONa)+underset("Water")(H_(2)O)+underset("dioxide")underset("Carbon")(CO_(2))`
`underset("acid")underset("Ethanoic")(CH_(3)COOH)+underset("HYDROGENCARBONATE")underset("Sodium")(NaHCO_(3))tounderset("acetate")underset("Sodium")(CH_(3)COONa)+underset("Water")(H_(2)O)+underset("dioxide")underset("Carbon")(CO_(2))`
Discussion
6087.

Explain the chemical properties of ethanoic acid.

Answer»

Solution :(1) Esterification reaction : Reaction of a CARBOXYLIC acid and an alcohol in the presence of an acid catalyst forms ester and WATER. This reaction is called an esterification reaction.
Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to form ester and water.
`underset("Ethanoic acid")(CH_(3)-underset(O)underset(||)C-OH)+underset("Ethanol")(HO-CH_(2)-CH_(3))overset("Acid")iffunderset("Ethyl acetate (Ester)")(CH_(3)-underset(O)underset(||)C-O-CH_(2)CH_(3))+underset("Water")(H_(2)O)`
Esters are SWEET smelling liquids and are used in making perfumes and flavouring agents.
A reaction of an ester with an alkali forming an alcohol and sodium SALT of carboxylic acid is called saponification reaction.
On treating with sodium hydroxide, which is an alkali (base), the ester is converted back to alcohol and sodium salt of carboxylic acid.
`underset("Ethyl acetate")(CH_(3)COOC_(2)H_(5))overset(NaOH)tounderset("Ethanol")(C_(2)H_(5)OH)+underset("acetate")underset("Sodium")(CH_(3)COONa)`
(2) Reaction with a base (Neutralisation) :
Like mineral acids `(HCI, HNO_(3), H_(2)SO_(4))`, carboxylic acid reacts with a base to form salt and water. This is called neutralisation reaction.
Ethanoic acid reacts with sodium hydroxide and forms sodium ethanoate (salt) and water.
`underset("Ethanoic acid")(CH_(3)-underset(O)underset(||)C-OH)+underset("hydroxide")underset("Sodium")(HO-Na)tounderset("Sodium ethanoate")(CH_(3)-underset(O)underset(||)C-ONa)+underset("Water")(H_(2)O)`

(3) Reaction with carbonates and hydrogen-carbonates : Ethanoic acid reacts with carbonates and hydrogencarbonates to form a salt, water and carbon dioxide.
Here, the salt formed is sodium acetate.
`underset("acid")underset("Ethanoic")(2CH_(3)COOH)+underset("carbonate")underset("Sodium")(Na_(2)CO_(3))tounderset("acetate")underset("Sodium")(2CH_(3)COONa)+underset("Water")(H_(2)O)+underset("dioxide")underset("Carbon")(CO_(2))`
`underset("acid")underset("Ethanoic")(CH_(3)COOH)+underset("hydrogencarbonate")underset("Sodium")(NaHCO_(3))tounderset("acetate")underset("Sodium")(CH_(3)COONa)+underset("Water")(H_(2)O)+underset("dioxide")underset("Carbon")(CO_(2))`
Discussion
6088.

Explain the cause of shoots of the plants bending towards light.

Answer»

Solution :STEMS are POSITIVELY phototropic and bend towards the direction of light the movemene is due to occurrence of more auxin on the DARKEN side and lesser auxin on the ILLUMINATED side as a result there in more growth on the darker side which causes the stem to bend towards light.
Discussion
6089.

Explain the breakdown of glucose in aerobic respiration and anaerobie respiration.

Answer»

Solution :i) In the presence of oxygen : When BREAKDOWN of glucose is carried out in the presence of oxygen in a CELL, it is called as acrobic respiration, Glucose is converted into a 3 carbon molecule called pyruvate which futher breakdown in the presence of oxygen to form carbondioxide and water. ENERGY is released in this process:

In the ABSENCE of oxygen : When breakdown of glucose is carried out in the absence of oxygen in a cell. It is called as anaerobic respiration. This process is called as fermentation in microbes. Ethyl alcohol or LACTIC acid is produced by the breakdown of pyruvato
Discussion
6090.

Explain the bonding in methane molecule using electron dot notation.

Answer»

SOLUTION :
Discussion
6091.

Explain the amphoteric nature of zinc oxide and aluminium oxide

Answer»

Solution :On warming zinc oxide with dilute sulphuric, the zinc oxide dissolves rapidly and forms clear solution of zinc sulphate.
Similarly, when aluminium oxide is warmed with dilute sulphuric acid forms aluminium sulphate.
`ZnO + underset((dil))(H_(2)SO_(4)) RARR ZnSO_(4) + H_(2)O`
`Al_(2)O_(3) + underset((dil))(3H_(2)SO_(4)) rarr Al_(2) (SO_(4))_(3) + 3H_(2)O`
On warming zinc oxide with concentrated sodium hydroxide or potassium hydroxide, the zinc oxide rapidly dissolves to form clear solution of sodium zincate or potassium zincate.
Similarly, aluminium oxide reacts with concentrated sodium hydroxide to form sodium metaluminate.
`ZnO + 2NaOH rarr Na_(2)ZnO_(2) + H_(2)O`
`Al_(2)O_(3) + 2NaOH rarr 2NaAlO_(2) + H_(2)O`
As the oxides of zinc and aluminium react with acids as WELL as alkali to form salt and water, they are amphoteric in nature.
Discussion
6092.

Explain the addition and substitution reaction with the help of examples. C_2H_6 undergoes substitution reaction but not addition reaction. Why?

Answer»

Solution :Substitution reaction : Those reactions in which an atom or group of atoms of a compound are replaced by other atom or group of atoms are called substitution reactions.
`underset("methane")(CH_(4)) + underset("chlorine")(Cl_(2)) overset("sunlight")(rarr)underset("CHLOROMETHANE")(CH_(3) Cl) + underset("hydrogen chloride")(HCI)`
Addition reaction : Those reactions in which two or more molecules or compounds are combined to form a large molecule or compounds, are called addition reaction. lt takes place in unsaturated hydrocarbon
`CH_(2)= CH_(2) + H_(2) underset("Ni")(rarr) C_(2) H_(6)`
Presence of multiple bonds (double and triple bonds) between carbon atoms in the chain of hydrocarbon is one of the essential condition for addition reaction.
As ethane has no double or triple bond, it does not undergo addition reaction, rather it goes for substitution reaction.
OR
Cleansing ACTION of Soap : A soap molecule consists of two dissimilar parts :
(i) A short ionic part comprising the carboxylate salt -`"COO"^(-) Na^(+)`which is water soluble.
(ii) A long hydrocarbon chain which is HYDROPHOBIC.
When soap is dissolved in water, it forms a colloidal suspension. In this colloidal suspension, the soap molecules duster together to form micelles and remain radially suspended in water with the hydrocarbon end towards the centre and the ionic end directed outward. The dirt particles always adhere to the oily or greasy layer present on the skin or clothes. When a dirty doth is dipped into a soap solution, its nun-polar hydrocarbon end of micelles gets attached to the grease or oil present in dirt and polar end rema.ins in water layer.
The mechanical action of RUBBING subsequently, dislodges the oily layer from the dirty surface shaping it into small globules. A stable emulsion of oil in water is formed. The emulsified oil or grease globules bearing the dirt can now be readily washed with water.
(ii) In hard water, soap reacts with calcium and magnesium salts which are present in hard water and form insoluble substances called scum. Thus scum is insoluble and floats on the surface of water.
When soap is shaken with hard water, which CONTAINS `Ca^(+2) and Mg^(+2)` ions, very less lather is formed and thus cleaning of clothes equire more soap.
Discussion
6093.

Explain the action of steam with iron .

Answer»

SOLUTION : `3Fe+4H_(2)OrightarrowFe_(3)O_(4)+H_(2)uparrow`
Discussion
6094.

Explain the cleansing action of soaps.

Answer»

SOLUTION :CLEANSING ACTION of SOAPS and DETERGENTS.
Discussion
6095.

Explain the action of phenolphthalein indicator in the titration of acetic acid, sodium hydroxide

Answer»

Solution :Acetic ACID is a WEAK acid having a pH value of more than 6. Sodium hydroxide is a strong base and additionsof `OH^(-)` ions neutralises the `H^(+)` ions formed by the dissociation of acetic acid. Since `H^(+)` ion concentration is very low, the addition of further `OH^(-)` ions increases the pH value ABRUPTLY. Therefore, the titration range of this reaction lies between 6.5 and 10.0.
The pH range of phenolphthalein is between 8.2 and 10.0 hence, it undergoes colour change in this range. Hence, it ACTS as a suitable indicator for this titration
Discussion
6096.

Explain the action of heat on Iron .

Answer»

SOLUTION :REACTION with air or oxygen : On heatingin air, iron formsmagneticoxide .
`3FE + 2O_3 + Fe_2O_4`(BLACK )
Discussion
6097.

Explain the action of dilute nitric acid with copper .

Answer»

Solution : Copper reacts with DIL - `HNO_(3)Rightarrow3Cu(NO_(3))_(2)+2NOuparrow+4H_(2)O`
copper NITRATE Nitric OXIDE
Discussion
6098.

Explain the action of dilute hydrochloric acid on the following with chemical equation. (a) Magnesium ribbon (b) Sodium hydroxide (c ) Crushed egg shells

Answer»

Solution :Hydrogen gas is formed
`MG(s) + 2HCl(aq) rarr MgCl(aq) + H_(2)(g) UARR`
(b) Sodium chloride and water are formed
`NaOH + HCl rarr NaCl + H_(2)O`
(c ) crushed EGG shells are made of calcium CARBONATE `(CaCO_(3))` which reacts with HCl to give brisk EFFERVESCENCE due to `CaCO_(3) (s) + 2HCl(aq) rarr CaCl_(2)(aq) + H_(2)O(i) + CO_(2)(g)`
Discussion
6099.

Explain the action of Aluminum with air .

Answer»

Solution :On HEATING at `800^(@)C`, aluminum bruns in AIR very brightly forming its oxide and NITRIDE.
`4Al+3O_(2)rightarrow2Al_(2)O_(3)` (Aaluminium oxide )
`2Al+N_(2)rightarrow2AIN`(Aluminium nitride)
Discussion
6100.

Explain the acidic character of oxide of elements down a group and across a period.

Answer»

SOLUTION :The acidic character of OXIDE of elements decreases down a group and INCREASES across a period, from left to right.
Discussion