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8201.

A white coloured powder is used by doctors for supporting fractured bones. (a) Write chemical name and formula of the powder. (b) When this white powder is mixed with water a hard solid mass is obtained. Write balanced chemical equation for the change.

Answer»

Solution :(a) CALCIUM sulphate hemihydrate.
`CaSO_(4).(1)/2H_(2)O`
(b) `CaS_(4).(1)/2H_(2)O+3/2H_(2)OtoCaSO_(4).2H_(2)O`
Discussion
8202.

(a) Which two criteria did Mendeleev use to classify the elements in his periodic Table? (b) State Mendeleev's periodic law. ( c) Why could no fixed position be given to hydrogen in Mendeleev's Periodic Table ? (d) How and why does the atomic size vary as you go (i) from left to right along a period (ii) down a group ?

Answer»

Solution :(a) (i) Increasing order of atomic mass as physical property and similarities in chemical properties of elements.
(ii) The formulae and nature of hydrides and oxides formed by elements was treated as basic chemical property for its CLASSIFICATION.
(b) Mendeleev.s PERIODIC Law: Properties of elements are the periodic functions of their atomic masses.
( c) It is because it resembles both with alkali metals as well as halogens.
(d) (i) Atomic size goes on decreasing from left to right because one PROTON and one electron is being added successively therefore, force of attraction between valence electrons and nucleus increases, therefore, atomic size decreases.
(ii) The atomic size goes on increasing from top to bottom in a GROUP because number of SHELLS keep on increasing therefore, distance between nucleus and valence electrons increases.
Discussion
8203.

(a) Which two criteria did Mendeleev use to classify the elements in his periodic table ? (b) State Mendeleev's periodic law. (c) Why is it not possible to give a fixed position to hydrogen in Mendeleev's periodic table ?

Answer»

Solution :(a) (i) Increasing order of atomic mass as physical properties and similarities in chemical properties of elements.
(II) The formulae and nature of hydrides and OXIDES formed by elements was TREATED as basic chemical properties for its classification.
(b) Mendeleev.s Periodic Law : The properties of elements are the periodic function of their atomic masses.
(C) It is because it RESEMBLES both with alkali metals as well as halogens.
Discussion
8204.

(a) Which of the following burn with a yellow flame: C_2H_5OH, C_2H_4, "or" C_2H_6 ? (b) Write a balanced chemical equation to show the burning of ethanol in oxygen . (c) Name an oxidizing agents which can convert ethanol into ethanoic acid.

Answer»

Solution :a] `C_2H_4`.
b] `C_2H_5OH + 3O_2 to 2CO_2 + 3H_2O`.
C] ALKALINE POTASSIUM PERMANGANATE.
Discussion
8205.

(a) Which disease is caused in human beings due to depletion of ozone layers in the atmorphere. (b) What step is being taken to limit the damage to the ozone layer.

Answer»

Solution :Skin cancer is caused in HUMAN beings due to the depletion of oozone layer in the atmosphere.
Judicious use of acrosol SPRAY propcllants such as flurocarbons and chlorofluro-carbons which CAUSE depeletion or HOLE in ozone layer.
Control over large scale nuclear explosions and limited use of supersonic planes.
Discussion
8206.

(a) When calcium metal is added to water, the gas evolved does not catch fire but the same gasevolved on adding potassium metal to water catches fire. Explain why?(b) Name a metal for each case :(i) It displaces hydrogen gas from nitric acid. (ii) It does not react with any physical state of water. (iii) It does not react with cold as well as hot water but reacts with steam.

Answer»

SOLUTION :(a) Reaction of potassium with water is so violent and exothermic that the evolved hydrogen catches fire.
`2K(s) + 2H_2O (l) to2KOH (aq) + H_2(g)`
The reaction of CALCIUM with water is less violent. The heat evolved is not sufficient for hydrogen to catch fire.
`CA(s) + 2H_2O(l) to Ca(OH)_2(aq) + H_2(g)`
(B)(i) Magnesium(ii) Copper (iii) Aluminium
Discussion
8207.

Explain the following reactions with one example for each giving relevant chemical equations : (i) Hydrogenation reaction, (ii) Oxidation reaction, (iii) Substitution reaction, (iv) Saponification reaction.

Answer»

SOLUTION :When carbonic ACID reacts with alcohol n the presenee of cone. `H_(2)SO_(4),` pleasant fruity smelling compound is formed this type of reaction is called esterification reaction.
`underset("Ethanoic acid")(CH_(3)COOH_(1))+ underset("Ethanol")(C_(2)H_(5)OH_(1))underset(H_(2)SO_(4))overset("Alkaline")rarr underset("Ethyl ethanoate")(CH_(3)COOC_(2)H_(5(1)))+ underset("Water")(H_(2)O_(1)`)
(i) Oxidation reaction :
`underset("Ethanol")(CH_(3)CH_(2)OH)+2[O] underset("KMnO"_(4))overset("Alkaline")rarr underset("Ethonoic")(CH_(3)COOH+H_(2))O`
(ii) Addition rection:
`underset ("Ethene")(CH_(2))=CH_(2)+H_(2)underset("573K")overset("Ni")rarr CH_(3)- CH_(3)`
(iii) Substitution reaction :
`underset("Methane")(CH_4)+Cl_(2) overset("Sunlight")rarr underset("METHYLCHORIDE")(CH_(3)CL+HCl)`
Discussion
8208.

How do you distinguish experimentally between an alcohol and a carboxylic acid ?

Answer»

Solution :THEFORMULA for cyclopentane is `C_5 H_(10)` . Its electron dot structure is given below.

We can distinguish betwecn an alcohol and a CARBOXYLIC acid on the basis of their reaction with carbonate and hydrogen carbonates. Acids reacts with carbonate and hydrogen carbonate to EVOLVE `CO_2` GAS that turms lime water milky.
Metal carbonate / metal hydrogen carbonate + carboxylic acid.
`"" darr`
Salt + water + CARBONDIOXIDE .
Alcohols on the other hand, do not react with carbonates and hydrogencarbonates.
Discussion
8209.

a) What property do all elements in the same column of the periodic table as boron share? b) What property do all elements in the same column of the periodic table as fluorine share?

Answer»

Solution :(a) All the ELEMENTS have 3 valency and their OXIDES are generally AMPHOTERIC.
(b) All the elements have valency 1, high non metallic character and from IONIC bonds.
Discussion
8210.

(a) What property do all elements in the same column of the Periodic Table as boron have in common? (b) What property do all elements in the same column of the Periodic Table as fluorine have in common?

Answer»

SOLUTION :(a) All the elements in the same column as boron have three electrons in the valence SHELL. That is all the elements are trivalent.
(b) All the elements in the same column as fluorine have ONE electron in the valence shell, that is all the elements are MONOVALENT.
Discussion
8211.

(a) What property do all elements in the same column of the Periodic Table as boron have in common?(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?

Answer»

SOLUTION :(a) They all have a valency of 3.
(B) They all have a valency of 1 because all have 7 VALENCE electrons.
Discussion
8212.

a) What is Tyndall effect? Give two examples for Tyndall effect.

Answer»

Solution :(a) The scattering of light by the particles in a colloidal medium is called Tyndall effect.
Examples :
Sunlight passing through a dense FOREST.
Focusing a beam of red light-in milk.
Passing a blue light to a DARK room.
(b) The ability of eye to focus both near and distant objects, by adjusting the focal length is called power of accommodation of the eye. When the ciliary muscles are relaxed, the eye lens becomes thin, the focal length increases and the distant objects are clearly visible to the eyes. To see the near by objects clearly, the ciliary muscles contract making the eye lens thicken. THUS the focal length of the eye lens decrease and the near by objects become visible to the eyes. Hence the human eye lens is ABLE to ADJUST its focal length to view both distant objects
Discussion
8213.

a) What is thermite reaction ? b) Q is an element which is one in copper, zinc, aluminium and iron, its properties are as follows. i) Q_(2)O_(3) is found in nature but not affected by water. ii) Two chlorides with formula QCI_(2) and QCI_(3) are formed by the metal. Identify the metal

Answer»

Solution : a) The displacement reaction which is highly exothermic and the metal produced is in molten state is CALLED thermite reaction.
i). Since the oxide of the metal is `Q_(2)Q_(3)` its valence is 3. therefore out of the mentioned metal only adumimium and iron can be the metal with PROPERTIES mentioned above.
ii) `QCI_(2)` and `QCI_(3)` must be iron as it shows varible VALENCY of two and three. `FeCl_(2)` and `FeCl_(3)` are the chlorides.
Discussion
8214.

a) What is the resistance of a conductor? Mention the factors on which the resistance of a conductor depend. b) b) An electric bulb of 200 Omegadraws a current of 1 ampere. Calculate the power of the bulb the potential differenceat its ends and the energy in KWh consumed burning it for 5h.

Answer»

Solution :a) Resistance of a conductor is the property of a conductor by VIRTUE of which it opposes the flow of current through it. The resistance of the conductor depends i) on its length II) on its area of CROSS section and ii) on the nature of its materials.
b) Power of the bulb
Power of the bulb, `P = I^2 R = (1)^2 xx 200`
`P = 200 W`
Energy CONSUMED by bulb in 5h in burning.
= Power x Time
= 200 x 5
= 1000 wh = 1 kwh.
Discussion
8215.

(a) What is the activity series of metals ? Arrange the metals Zn, Mg, Al, Cu and Fe in a decreasing order of reactivity. (b) What would you observe when you put (i) some zinc pieces into blue copper sulphate solution ? (ii) some copper pieces into green ferrous sulphate solution ? (c ) Name a metal which combines with hydrogen gas. Name the compound formed.

Answer»

Solution :(a) (i) Blue colour of copper SULPHATE solution would slowly disappear.
(ii) No CHANGE would be noticed.
(c ) Sodium combines with hydrogen to form sodium hydride.
`2Na + H_(2)rarr UNDERSET("SOD. hydride")(2NaH)`
Discussion
8216.

(a) What is the action of litmus on: (i) Dry ammonia gas (ii) Solution of ammonia gas in water (b) State the observations you would make on adding sodium hydroxide to aqueous solution of : (i) Ferrous sulphate (ii) Aluminium chloride Give balanced chemical equations.

Answer»

SOLUTION :(a) (i) No change in colour
(ii) red litmus turns BLUE
(b) (i) `2NaOH(aq)+FeSO_4(aq) to FE(OH)_2(s)+Na_2SO_4`
Sodium hydroxide Ferrous sulphateFerrous hydroxide Sodium sulphate
(III) `3NaOH(aq)+AlCl_3(aq) to AL(OH)_3(s)+ NaCl(aq)`
Sodium Hydroxide Aluminium chloride Aluminium Hydroxide Sodium chloride
Discussion
8217.

a) What is meant by the term speciation. List four factors which could lead to speciation. b) Name the two laws of inheritance postulated by Mendel.

Answer»

SOLUTION :a) SPECIATION is the evolution of reproduction isolation among once interbreeding population factors which can lead to speciation are:
* Genetic drift : over generations, genetic drift may accumulate which lead to speciation
*Natural selection : Natural selection which may give RISE to speciation.
*Severe DNA change
*A variation may occur which does not allow sexual act between two groups.
*b) i) The law of regeneration
ii) The law of INDEPENDENCE assortment.
Discussion
8218.

(a) What is myopia ? State the two causes of myopia (b) Why is the normal eye unable to focuson an object placed wtithin 10 em from the eye?

Answer»

Solution :Myopic cye can SEE objects al SHORL distance inability of the eye in viewing long distant objects the image.falls before retina causcs of myopia.
(i) Elongation of eye ball
(ii) Excessive curvature in
(B) A NORMAL eye is unable to clearly see the objects placed closer then 25 CM because the ciliary muscles of eyes are unable to contract beyond a certain limit
When the objcct is placed at a distance less or more than 25 cm from the eye than the object appears blurred and induces strain in the eyes.
Discussion
8219.

a) What is meant by least distance of distinct vision? b) What happens to the image distance in the eye when we increases the distance of an object from the eye.

Answer»

Solution :a) It is the minimum distance up to which EYE can see clearly and is CALLED the least distance of distinct vision.
b) The size of the eye can CHANGE, so the image distance is fixed when we increase the distance if the eye does not change, due to power of ACCOMMODATION of the eye, focal length of the eye lens is changed, which compensates the increase in object distance. Hence image distance remains fixed and image is formed on the RETINA of the eye.
Discussion
8220.

Draw the structure of the following compounds and identify the functional group present in them. (i) Butanoic acid (ii)Bromopropane (iii)Butyne

Answer»

Solution :It is the reaction that formS soap when an ESTER reacts with water in the PRESENCE of base a SALT of carboxylic acid and an alcohol are produced. Sucha reaction is called saponification.
For example: When ETHYL ethanote is heated with a solution of sodium hydroxide sodium cthanote and ETHANOL are produced.
`CH_(3)COOC_(2)H_(5)+NaOHrarrCH_(3)COONa+C_(2)H_(5)OH`
Function group is carboxylie acid

(ii) Function group is Bromine
`H - underset("H")underset(|)overset("H")overset(|)(C)-underset("H")underset(|)overset("Br")overset(|)(C)- underset("H")underset(|)overset("H")overset(|)(C)- underset("H")underset(|)overset("H")overset(|)(C)-H`
Discussion
8221.

(a) What is isomerism ? Name the isomers of butane. (b) Name the air pollutant liberated during incomplete combustion of methane. (c) Name the importance of hydrogenation of oils.

Answer»

Solution :(a) PHENOMENON in which organic compounds have same molecular formula with different structural arrangement of atoms in them is known as isomerism.
n-butane and iso-butane.
(B) CARBON monoxide (CO)
(c) Hydrogenated oils.
(i) have more shelf life, easy to TRANSPORT.
(ii) do not produce foul smell.
Discussion
8222.

a) What is hypermetropia? What are the two causes of theis defect of vision. b) What is the colour of the clear sky during day time. Give reason for it.

Answer»

Solution :a) Hypermetropia is the DEFECT in which a person can see distance objects clearly but cannot see the nearby objects.
The two possible causes of this defect are :
* INCREASE in the FOCAL length of the eye lens,
* EYEBALL gets shortened.
b) When sunlight passes through the atmosphere having the molecules of air and other fine particles whose size is smaller than the wave length of visible light these molecules and particles scatter the blue colour more strongly than the other colours of spectrum as the wave length of blue colour is more. This scattered blue light enters our eye, so the colour of sky apepars blue to us during day TIME.
Discussion
8223.

a) What is fertilisation? Distinguish between external fertilisation and internal fertilisation. What is the site of fertilisation in human beings. b) How does growing embryo get nutrition from the mother's blood?

Answer»

Solution :Fertilisation is defined as the FUSION of a male gamete (sperm) with a female gamete (an -ovum or egg) to form a żygote during sexual reproduction external fertilisation.
* The fusion of male gamete (sperm) and female GAMATE (ovum) occur OUTSIDE the body. Both individuals discharge their gamates outside the body. * Development occurs outsie the body.
Ex: Frog.
Internal fertilisation :* The fusion of gametes occurs inside the body.
* Only the male discharge sperm into female gentital tract.
* Development occurs inside the body. Ex: Humans, cattle etc.
The site of fertilisation in human beings is in the fallopian tube of female reproductive system.
The embryo gets nutrition from the mother.s BLOOD with the help of a special tissue called placenta. This is a disc which is embedded in the UTERINE wall and transfer glucose and oxygen from the mother to the embryo.
Discussion
8224.

a) What is hydrogenation? What is its industrial application. b) Give the names of the following i) An aldehyde derived from ethane. ii) Ketone derived from butane iii) Compound obtained by the oxidation of ethanol by chromic anhydride.

Answer»

Solution :Addition of hydrogen to unsaturated hydrocarbons in presence of a catalyst such as nickel or palladium to FORM SATURATED hydrocarbons is called hydrogenation For Example:-

Industrial application:-
The process of hydrogenation is used in industry to convert vegetable oils to vanaspathi ghee

The vegetable oil contains a number of unsaturated carbon chain having double BONDS between carbon atoms when `H_(2)` is bubbled through vegetable oils in presence of nickel as catalyst at 437K some of the double bonds add `H_(2)` to form saturated carbon chain. As a result of this partial hydrogenation, oils are converted into solid fats.
B)i)Ethanal(`CH_(3)CHO`)
ii) Butanone (`CH_(3)CO CH_(2)CH_(3)`)
III) Ethanol (`CH_(3)CHO`).
Discussion
8225.

(a) What is efflorescence ? Name one compound which shows efflorescence. Support your answer with reason. (b) Give three important properties of washing soda.

Answer»

SOLUTION :(a) The loss of water of crystallisation from a hydrated SALT when left open in air is called efflorescence.
When crystals of washing soda,`Na_2CO_3 . 10H_2O`are left open in air they lose nine molecules of water of crystallisation and form monohydrate. This process is called efflorescence.
`overset("Heat")to Na_2CO_3. H_2O + 9H_2O`
(b) IMPORTANT properties of washing soda .
1. Sodium carbonate is a transparent crystalline solid. It exists as a decahydrate `(Na_2CO_3. 10H_2O)` containing 10 molecules of water of crystallisation .
2. It is readily soluble in water. It dissolves in water to form an alkaline solution, which turns red litmus solution blue. This shows that an aqueous solution of sodium carbonate is alkaline.
3. Action of heat. When crystals of washing soda are left open in air they lose nine molecules of water of crystallisation and form monohydrate. This process in known as efflorescence. Thus, washing soda is efflorescent.
`underset("Sodium carbonate (decahydrate)")(Na_2CO_3. 10H_2O) underset("air) overset("Exposure to ") tounderset("Sodium carbonate (monohydrate)")(Na_2CO_3. H_2O + 9H_2O)`
On heating above 373 K, washing soda does not decompose but loses all its water of crystallisation to form anhydrous salt. Thus, the monohydrate becomes completely anhydrous and changes to a white powder called soda ASH.
Discussion
8226.

a) What is a universal indicator ? b) A milk man adds a very small amount of baking soda to fresh milk. i) Why does he shift the pH of the fresh milk from 6 to slightly alkaline. ii) Why does this milk take a long time to set as curd.

Answer»

Solution :a) A universal INDICATOR is a mixture of a number of indicators which shows different colours at different pH values,
b) Since the fresh milk is acidic it turns sour EARLY in presence of baking soda, milk become alkaline and does not turn sour easily because of alkali does not allow the milk to become more acidic early
ii) When the milk sets to curd the pH decreases i.e., it becomes more acidic the presence of alkali does not allow it to become more acidic easily hence it will TAKE a long TIME to SET as curd.
Discussion
8227.

(a) What is a slat ? Give the names and dormulae of any two salts. Also name the acids and beses from which these salts may be obtained. (b) What is meant by a family of salts' ? Explain in with examples. , (c ) Whatis ment by 'hydrated' and 'anhydrous' slts ? Explain with examples. (d) Write the names, formulae and colours of any two hydrated aslts. (e) What will be the colour of litmus in an aqueous solution of ammonium chloride salt ?

Answer»
Discussion
8228.

Write the balanced chemical equations for the following chemical reactions . (i) Potassium bromide reacts with Barium iodide. (ii) Zinc carbonate is heated.

Answer»

Solution :a) An equation in which the number of ATOMS of each on the two SIDE of an equation is equal is CALLED a BALANCED CHEMICAL equation. ii) ` ZnCO_3 (s) to ZnO(s)+ CO_2(g)`
Discussion
8229.

(a) What happens when MgSO_4 .7H_2 O is heated? Write the appropriate equation. (b) Define solubility.

Answer»

Solution : (a)` MgSO_4 . 7H_2 O `has water of crystallization is 7. When magnesium SULPHATE heptahydrate crystals are gently heated, it loses seven water molecules and becomes anhydrous magnesium sulphate.
` UNDERSET("magnesiumsulphateheptahydrate")( Mg SO_4 .7H_2 O) underset("cooling")overset("Heating")hArrunderset("anhydrousmagnesiumsulphate ") ( MgSO_4+ 7H_2 O)`
(B) SOLUBILITY: It is DEFINED as the number of grams of a SOLUTE that can be dissolved in 100 g of a solvent to form its saturated solution at a given temperature and pressure.
Discussion
8230.

a) What factors could lead to the rise of a new species. b) Only variations that can have an advantage to an individual organism will survive in a population. Do you agree with this statement why or why not.

Answer»

Solution :a) Natural selection, genetic drift and acquisation of traits during the lift-time of an individual can give rise to new species.
b) In species variations that offer survival advantage are naturally selected individuals ADJUST to their environment with the help of those selected are passed on to their progeny evolution of organisms occurs as a result of this natural selection. However there can be some other variations which do not offer any survival advantage of some genes even if they are not IMPORTANT for survival. This accidental change in the FREQUENCY of gene in small population is reffered to as genetic drift. THUS genetic drift provides DIVERSITY without any survival advantage.
Discussion
8231.

a) What happens if too much of acid is produced in the stomach? What is the remedy for this situation? b) What is water of crystallization? c) Write any two uses of plaster ofparis .

Answer»

Solution :(a) If too much of acid is produced in the stomach it causes hyperacidity (Irritation and pain). To get rid of this pain we have to use bases called antacids. It neutralises EXCESS of acid and gives relief from pain caused by hyperacidity.
(B) the fixed number of water molecules present in one formula unit of a crystaline salt is called water of crystallisation. Plaster of paris is PREPARED by heating gypsum to a temperature of `100^@C.`
The following reaction takes place :
` CaSO_4 . 2H_2O overset(100^@C)(to) CaSO_4 . 1/2 H_2O+ 1/2H_2O `
i) it is used to prepare chalks .
ii) It is used to make CASTS and MOULDS.
Discussion
8232.

(a) What do you see when a magnesium ribbon is burnt ? Is magnesium oxidised or reduced inthis reaction ? (b) Define corrosion.

Answer»

Solution : (a) MAGNESIUM burns with a dazzling light producing white ash of magnesium OXIDE.
`2Mg + O_2to 2MgO`
Magnesium is oxidised because it combines with OXYGEN.
(b) CORROSION is defined as the combination of a metal with atmospheric oxygen, carbon dioxideand moisture to form an oxide, carbonate, etc. Corrosion causes DAMAGE to car bodies, bridges, etc.
Discussion
8233.

What do you mean by a precipitation reaction ? Explain by giving examples.

Answer»

SOLUTION :(a) Any rcaction in with an insoluble solid is produced is called a precipitate reaction. For cxample:
`underset ("Choride Sulphate")underset("Barium Sodium")(BaCl_(2aq)+Na_(2)SO_(4aq))overset("Heat")rarr underset("Sulphate") underset("Barium")(BaSO_(4("S")))darrunderset("Choride")underset("Sodium")(2NaCl_((aq)))`
(b) Oxidation : It is defined as process which involves gain of oxygen
For exumple :
`underset("Magnesium")2Mg_(("s")) underset("Oxygen")(+O_(2)("g"))rarr underset("Magnesiumoxide")(2MgO_(("s")))`
Reduction : t is defined AL process which INVOLVER loss of oxygen.
For EXAMPLE :
`underset("oxide")underset("copper")(CuO_(("s")))+ underset("hydrogen")(H_(2("g")))overset("Heat")rarrunderset("copper")(Cu_(("s"))+)underset("water")(H_(2)O_(("g")))`
Discussion
8234.

a) What are trophic levels ? b) What will happen if we kill all organisms in one tropic level.'

Answer»

Solution :a) Trophic levels are the feeding level in an ecosystem. the trophic level of living beings represent their placement in a food CHAIN it also tell the order of CONSUMPTION and energy transfer throughout the ecosystem.
b) If we kill all the organisms in ONE trophic level the following effects will taken place
* The POPULATION of organisms in previous tropic level will increase.
* The organisms in next trophic level will not be able to get the food so they will MIGRATE to some other ecosystem or die.
* It will cause an ecological imbalance in the food chain.
Discussion
8235.

(a) What are the periods and groups in a periodic table? Give two characteristics of each. (b) In terms of electronic condigurations, explain the variation in the size of the atoms of elements belonging to the same period and same group. (c) Given alongside is a part of the periodic table. As we move vertically downward from Li to Fr: (i) What happens to the size of atoms? (ii) What happens to their metalic character? (d) Name two properties of elements whose magnitudes change when going from top to bottom in a group of the periodic table. In what manner do they change? (e) Rewrite the following statement after correction, if necessary: Groups have elements with consecutive atomic numbers.

Answer»


SOLUTION :NA
Discussion
8236.

a) List any four reasons for adopting contraceptivemethods. b) If a woman is using copper - T will it help in protectingher from sexually transmitted diseases Why?

Answer»

Solution :Advantages of sexual reproduction.
* In sexual reproduction more VARIATIONS are produced thus it ensures SURVIVAL of SPECIES in a pollination.
* The new formed individual has characteristics of both the parents.
* Variations are more vaible in sexual mode then in asexual one. This is because in asexual reproduction, DNA has to function inside the inherited cellular apparatus.
b) Four reasons for adopting contraceptive methods are
* To INCREASE the gap between two children.
* To prevent unwanted pregnancy.
* To prevent transmission of STD.s
* To control POPULATIONS growth.
c) If a woman is using copper-T it will not help in protecting her from sexually transmitted diseases. Copper-T prevents only implantation in the uterus.
Discussion
8237.

a] What are metalloids? Write any two examples. b] Given below are some of the elements of the first group: Li, Na, K (their atomic numbers are 3, 11, and 19 respectively and they belong to 2nd, 3rd, and 4th period respectively). Arrange them in the decreasing order of their metallic character.

Answer»

Solution :a) Metallolds have properties in between those of metals and non-metals. Examples are SILICON and germanium.
B) Li, Na, and K are placed in group one below the other. Since metallic CHARACTER Increases down a group, K has the highest metallic character. HENCE, in decreasing order of metallic character, the arrangement is: `K > Na > Li.`
Discussion
8238.

(a) What are hydrocarbons? Give examples. (b) Give the structural differences between saturated and unsaturated hydrocarbons with two examples each. (c ) What is functional group? Give examples of four different functional groups.

Answer»

Solution :(a) Compounds of carbon and hydrogen are called hydrocarbons. For example, methane, ethane, etc.
(b) Saturated hydrocarbons contain carbon-carbon single bonds.
Unsaturated hydrocarbons contain at least one carbon-carbon double or triple bond.
`underset("Saturated hydrocarbons")(underset("Methane")(H-underset(H)underset(|)overset(H)overset(|)C-H)""underset("Ethane")(H-underset(H)underset(|)overset(H)overset(|)C-underset(H)underset(|)overset(H)overset(|)C-H))""underset("Unsaturated hydrocarbons")(underset("Ethene")({:(H),("\"),("/"),(H):}C=C{:(" H"),("/"),("\"),(" H"):})"" underset("Ethyne")(H-C-=C-H))`
(c ) An atom/group of atoms joined in a specific MANNER which is responsible for the CHARACTERISTIC chemical properties of the organic compounds is called a functional group. Examples are hydroxyl gropo (-OH), aldehyde group (-CHO), ketonic group `(underset("/")overset("\")(" "C)=O)`, carboxylic group (-COOH), etc.
Discussion
8239.

Two elements M and N beong to group I and II respectively and are in the same period of the periodic tabe. How do the follwoing properties of M and N vary ? Sizes of their atoms

Answer»

Solution : a) The vertical COLUMNS in the PERIODIC table are called group. The horizontal rows in the periodic table are called periods. b) 1. M and N belong to the same period but I and II. Therefore N will be smaller than Mas atomic size is decreasing from left to right. 2. M is more metallic than N. Metallic character goes on decreasing from left to right as tendency to lose electrons decreases DUE to decrease in atomic size. 3. Their valencies are 1 and 2 respectively in forming OXIDES. Valency goes on increasing first and then increases. 4. `MCI, NCI_2`are molecular formulae of their CHLORIDES.
Discussion
8240.

a) What are groups and period in the periodic table? b) Two element M and N belong to group I and II respectively and are in the same period of the periodic table. How do the following properties of M and N vary? 1) Size of their atoms 2) This metallic characters 3) Their valencies informing oxides. 4) Molecular formulae of their chlorides.

Answer»

Solution : a) The vertical columns in the periodic table are CALLED group. The horizontal rows in the periodic table are called periods.
b)1. M and N belong to the same period but group I and Ii. Therefore N will be SMALLER than M as a atomic size is decreases from left to right.
2. M is more metallic than N. Metlallic character goes on decreasing from left to right as tendency to lose electrons.
3.Their VALENCIES are 1 and 2 respectively in forming oxides. Valency goes on INCREASING first and then decreases.
4. MCI, `NCI_2` are molecules formulae of their CHLORIDES.
Discussion
8241.

(a) What are covalent bonds? Write the type of bonds present in N_(2) and CH_(4) molecules. (b) Why does carbon form compounds mainly by covalent bonding? (c) Write the IUPAC names of the following compounds? (i) C_(6)H_(6), (ii) C_(3)H_(7)Cl.

Answer»

SOLUTION :(a) For the definition of covalent bond,. The BONDS in `N_(2) and CH_(4)` molecules are of covalent NATURE.

(B)
(c) (i) `underset("BENZENE")(C_(6)H_(6)),(ii) underset("1-Chloropropane")(CH_(3)CH_(2)CH_(2)Cl) and underset("2-Chloropropane")(CH_(3)underset(Cl)underset(|)(C)HCH_(3))`
Discussion
8242.

(a) What are amphoteric oxides ? Choose the amphoteric oxides from amongst the following oxides :Na_2O, ZnO, Al_2O_3, CO_2, H_2O(b) Why is it non-metals do not displace hydrogen from dilute acids ?

Answer»

SOLUTION : (a) Metal OXIDES which react both with acids and bases to form salt and water are known asamphoteric oxides. Out of the GIVEN list, ZNO and `Al_2O_3` are amphoteric oxides.
(b) Elements which lie higher than HYDROGEN in the activity series are capable of displacing hydrogenfrom dilute acids. Non-metals lie below hydrogen in the activity series. Therefore, they do notdisplace hydrogen from dilute acids.
Discussion
8243.

A volatile solid soluble I n benzene would probably

Answer»

have electrovalent bonding
have covalent bonding
be a good CONDUCTOR of ELECTRICITY
be a SALT

Answer :B
Discussion
8244.

A vessel contains equal number of moles of helium and methane. Due to a hole in thevessel, half of thegaseous mixture effused out. What is theratioof the number of moles of helium and methane remaining in the vessel?

Answer»

Solution :(i) relation between molecular WEIGHT and rate of effusion
(II) determination of the ratio of the NUMBER ofmolecules of helium and methane which are effused out
(iii) CALCULATION of the ratio of the remaining molecules
(iv) `(2x)/3` moles
Discussion
8245.

A vessel contains double thenumber of moles ofhydrogen than oxygen. Due to a hole in thevessel, one-fouth of the gaseous mixture is effused out. What is the ratio of the number of moles of hydrogen and oxygen remaining in thevessel ?

Answer»

SOLUTION :(i) relation between number of moles of gases
(ii) relation between number of moles of gases effused and molecular WEIGHT
(iii) comparison of number OFMOLES of `H_(2) and O_(2)` effused
(IV) calculation of number of moles of `H_(2) and O_(2)` left over
(v) ` 28 : 17`
Discussion
8246.

A vessel contains equal masses of hydrogen, helium andmethane. Find out thefractions of thepartial pressures in the mixture.

Answer»

Solution :(i) fraction of number of MOLES of `CH_(4), H_(2) ` and He in the mixture
(ii) RELATION between mole fraction andtotal pressure
(iii) `(8P)/13,(4P)/13, P/13`
Discussion
8247.

(a) "Use of a condom is beneficial for both the sexes involved in a sexual act." Justify this statement giving two reasons. (b) How do oral contraceptive help in avoiding pregnancies? (c ) What is sex selective abortion? How does it affect a healthy society. (State any one consequence)

Answer»

Solution :(a) Use of condom is beneficial for both sexes because:
(i) It helps in spacing children.
(ii) It helps in preventing spread of STDS.
(b) Spermicidal applications by women, vaginal pills or oral contraceptive pills (OCPs) are used. OCPs are hormonal preparations which alter the hormonal LEVEL in female body.
(c ) medical termination of pregency (MTP) is a method that should be used only if the FOETUS has some defect, of if it is life-threatening to the mother. It should not be used as a contraceptive method.
Surgery can also be used for removal of unwanted pregnancies. These may be misused by people why do not want a PARTICULAR child, as happens in illegal sex-selective abortion of female foetuses. For a healthy society, the female-male sex ratio must be maintained. Because of reckless female foeticides, child sex ratio is declining at an alarming rate in some sections of our society, although prenatal sex determination has been prohibited by LAW.
Discussion
8248.

A universalindicator is used to determine the acidic or basic stength of a solution .

Answer»


ANSWER :T
Discussion
8249.

A universalindicator is

Answer»

an individual indicator
a mixture of INDICATORS
a solution of METHYL orange in ETHANOL
none of the above

ANSWER :B
Discussion
8250.

A trupositive ion of element 'X' has six electrons with I = 0 and five electrons with I = 2. (a) Predict the group and period to which 'X' belongs. (b) Dose the element show variable valencies? Justify.

Answer»

Solution :(a) 1 = 0 corresponds to 's' SUBSHELL and 1 = 2
corresponds to 'd' subshell. Further, six electrons
in 's' subshell and five electrons in 'd' subshell
means the ion should have the electronic
configuration `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(5)`. Since it is
a tripositive ion, the atom could have lost two
electtrons from 4s subshell and one electron
form 3d subshell. Therefore, atomic number is
26. Electronic configuration is [Ar] `3d^(6)4s^(2)` It
belongs to the VIII group and 4TH period.
(b) Yes. Since Fe is a transition element it shows
variable oxidationn state. In transition ELEMENTS,
the electrons enter into the penultimate shell
instead od calence shell. Energy difference
between ns and `(n -1)d`orditals is very less.
Hence, both ns and `(n -1)d` electrons are available for chemical bond formation. So,
they exhibit veriable valency.
Discussion