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3501.

Si+CrArr SiC. This chemical reaction is an example for :

Answer»

EXOTHERMIC reaction
ENDOTHERMIC reaction
DISSOCIATION reaction
displacement reaction

Solution :(II) endothermic reaction
Discussion
3502.

Shyam and Rema are student of Class-X. Shyam is very much organized and maintained. The teachers love him He earns a greater respect in the class whereas Rema is unorganised and always faces a lot of problems in handling life situations. In your opinion how organisation helps us in daily life?

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Solution :ORGANISATION makes our LIFE simple, EASY and systematic.
Discussion
3503.

Show the formation of Na_2Oand MgO by the transfer of electrons.

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SOLUTION :
Discussion
3504.

Show the formation of Na_2O and MgO by the transfer of electrons.

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Solution :Formation of `Na_2S`:
The atomic number of sodium is 11 and it has only one valence electron.
hence, electronic configuration of `_11Na` is 2,8,1
The atomic number of oxygen is 8 and it has 6 electrons in its valence shell.
Hence, electronic configuration of `_8O` is 2,6
Sodium has a tendency to lose the valence electron and oxygen has a tendency to gain the electron lost by sodium. SInce , sodium can lose only one electron of the valence shell and oxygen atom needs two electrons to complete its octet in the valence shell , two atoms of sodium combine with one atom of oxygen. By losing valence electron, sodium is CHANGED into an `Na^+` and by gaining two electrons lost by two sodium atoms, oxygen atom is changed into an oxide anion `O^(2-)` In this process both the atoms, sodium and oxygen. obtain the stable electronic configuration of the noble gas neon.
`Na_(2,8,1) to Na^(+)+e^(-)`
`O_(2,6)+2e^(-) to O_(2,8)^(2-)`
`2Na^(+)+O^(2-) to 2Na^(+)+O^(2-) or Na_2O`
The oppositely charged sodium ion, `Na^+` and oxide ion `O^(2-)` are now held together by electrostatic forces of attraction or by ionic or electrovalent bond, `Na_2O` is therefore, an ionic for electrovalent compound

Formation of `MGO`:
The atomic number of magnesium=12
Its electronic configuration isK,L,M
2,8,2
It has two electrons in its outermost shell, So the magnesium atom donates its 2 valence electrons and forms a stable magnesium ion, `Mg^(2+)` to attain the electronic arrangement of neon gas.
`Mg_(2,8,2) to Mg_(2,8)^(2+)+2e^(-)`
The atomic number of oxygen=8
Electronic configuration = K,I
2,6
It has six electrons in its valence shell. Therefore, its requires two more electrons to attain the stable electronic arrangement of neon gas. Thus, oxygen ACCEPTA two electrons DONATED by magnesium atom and forms a stable oxide ion `O^(2-)`
`O_(2,6)+2e^(-) to O_(2,8)^(2-)`
THe oppositely charged magnesium ions, `Mg^(2+)` and oxide ions, `O^(2-)` are held together by a strong FORCE of electrostatic attraction to form magnesium oxide compound `Mg^(2+)O^(2-) or MgO`

MgO is an ionic compound.
Discussion
3505.

Show the formation of MgO by transfer of electrons.

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SOLUTION :MgO :
`{:(Mg,RARR,Mg^(2+)+2e^(-),),("(2,8,2)",,"(2,8)",),(O+2e^(-),rarr,O^(2),),("(2,6)",,"(2,8)",):}`

MgO has `Mg^(2+)` and `O^(2-)` IONS.
Discussion
3506.

Show by chemical equations how roasting can convert sulphide ore into an oxide?

Answer»

SOLUTION :`2ZnS + 3O_2 to 2ZnO _ 2SO_2`
Discussion
3507.

Shivani is a of class X. She lives in a big house on the outskirts of Delhi. Her family has a kitchen garden at the back of the house in which various types of seasonal vegetables are grown. Shivani's parents have been getting good crops of vegetables for many years. But from last year, the yield of vegetables from the kitchen garden has reduced a lot. Shivani asken the gardener if he was putting any chemical fertiliser into the soil or not. The gardener told Shivani that he was putting a lot of ammonium sulphate fertiliser into the soil every time before sowing the fresh crop of vegetables and he has been doing this for any years to increase the yield of vegetables more and more. Shivani could now understand the problem. She then asked the gardener to mix a cerain substance with the soil uniformly before growing the next crop of vegetables. the gardener did the same. every one was happy to see that there was bumpercrop of vegetables this time. (a) What had happened to the soil in the kitchen garden over the years? Why? (b) Shivani took a little of soil from the kitchen garden stirred it with some water in a test tube, filtered it and tested and filtrate with universal indicator. The universal indicator. The universal indicator turned orange. What does this tell us about the nature of soil? (c) Why did the yield of vegetables in the kitchen garden reduce a lot? (d) What substance/ substances do you think Shivani asked the gardener to put in the soil of kitchen garden? (e) How did the addition of above substance/substances help the soil? (f) What values are displayed by Shivani in this episode?

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Solution :(a) The soil had turned too acidic over the years.This happened due to the continued use of AMMONIUM sulphate fertiliser. Ammonium sulphate is an acidic salt. When ammonium sulphate is added to soil, then ammonium ions (containing nitrogen) are absorbed by the roots of growingvegetable plants but sulphate ions go on accumulating in the soil. These sulphate ions form sulphuric acid which increases the acidity of soil.
(b) The fact that universal indicator turned orange, tell us that the soil of the kitchen garden is too acidic.
(c) The continued use of ammounium sulphate fertiliser made the soil in the kitched garden too acidic. The vegetable plants COULD not grow WELL in this highly acidic soil andhence the yield was reduced.
(d) Shivani may have asked the gardener to put quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) in the soil of kitchen garden.
(e) All these substances are bases which neutralise the excess acid present in the kitchen garden soil and reduce its acidity. This makes the soil fertile again and leads to a bumper crop of vegetables.
(f) The VALUES displacyed by Shivani are (i) Awareness (or knowledge) of how the chemical fertilisers change the nature of soil (ii) Understanding to neutralisation reactions of acids and bases, and (III) Desire to improve the yield of vegetables in the kitchen garden.
Discussion
3508.

S.H.E. stands for __________.

Answer»


ANSWER :STANDARD HYDROGEN ELECTRODE
Discussion
3509.

Shailesh lies in a bigh industrial city having a large numberof chemical industries onits outskirts. This city has also a very heavy traffic density. There is a biglake in the middle of this city which has much less water left init but the lake has still a large number of fish in it. During the last one and a half months, there ha been to much rain in the city with the pH of rain water being about 5.5. One day people found that many fish in the lake ha died. No one knew the reason for the death of fish in the lake or how the death of remaining fish in the lake could be prevented. Shailesh, who is a student of class X could understand the reason for the death of fish in lake. He also suggested an immediate solutioin for the prevention of death of more fish in the lake water. (a) What conclusion do you draw the fact that the rain water has a pH of about 5.5? What name is given to such a rain? (b) What makes the pH of rain water to be about 5.5? (c) What happens to lake water when too much rain water haivng pH of 5.5 collects in it? (d) Why have the fish died after the heavy rains? (e) Why suggestion do you think has been made by Shailesh to prevent the death of more fish in the lake? Why (f) What values are displayed by Shailesh in this episode?

Answer»

Solution :(a) The rain water having a pH of about 5.5 is acidic in nature. Such a rain is called acid rain.
(b) The chemical inductrias and heavy traffic (vehicles) in this city emit many harmful gases into the air and pollute it. The acidic gases (such as sulphur dioxide and nitrogen oxides) present in polluted air dissolve in rain water to produce acids. The presence of the acids lowers the pH of rain water to about 5.5 (making it quite acidic in nature).
(c) Too much acid rain can lower the pH of lake water appreciably and make it highly acidic.
(d) The high acidity of lake water caused by too much acid rains has caused the death of fish in the lake.
(e) Shailesh MIGHT have suggeted adding calcium carbonate to the lake water.This is because calcium carbonate neutralises the excess cid present in lake water (which comes from acid rain), reducing the acidity of lake water.This reduction in the acidity of lake water can PREVENT the death of more fish in the lake.
(f) The various values displayed by Shailesh in this EPISODE are (i) Awareness (or knowledge) of the occurrence of acid rain and its harmful effects on aquatic animals such as fish (ii) UNDERSTANDING of neturalisation reactioninvolving acidic and basic susbtances and (III) Concern to save the life of remaining fish in the lake.
Discussion
3510.

Several factories were pouring their wastes in rivers A and B. Water samples were collected from these two rivers. It was observed that sample collected from river A was acidic while that of river B was basic. The factorieslocated nearnear A and B are

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SOAPS and DETERGENTS factories near A and alcohol distillerynear B.
Soaps and detergents factories near B and alcohol distillerynear A.
Lead storage BATTERY MANUFACTURING factories near A and soaps and detergentsfactories near B.
Lead storagebattery manufacturing factories near B and soaps and detergents factories near A.

Solution :Lead storage battery manufacturing factories near A and soaps and detergentsfactories near B.
Discussion
3511.

Sequence the following steps involved generally in the extraction of a metal in pure form from its ore, the extraction of a metal in pure form from its ore. (1) The metal obtained from its oxide requires further purification for end use. (2) The ore shoud be converted to its oxide form. (3) The ore is beneficial to us if it is hand-picked then metal crushed and ground, and later subjected to Pulverisation as per the requirement. (4) The ore in the form of oxide is required to be reduced. (5) Dressed ore is required for it to be concentrated.

Answer»

5 3 2 4 1
3 5 2 4 1
3 5 2 1 4
3 5 4 2 1

Solution :(i) The ore is BENEFICIAL to us if it is hand-picked and then ore is crushed and grounded, and later subjected to Pulverisation as per the requirement.
(II) Dressed ore is required to be concetrated.
(iii) Ore is required to be converted to its oxide form.
(iv) Ore in the form of oxide its oxide requires reduced.
(v) The metal obtained from its oxide requires further PURIFICATION for end use.
Discussion
3512.

Series of 14 elements placed below the periodictable having atomic no. from 90 to 103 [Th to Lr]

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SOLUTION :ACTINIDES .
Discussion
3513.

Series of 14 elements placed below the periodictable having atomic no. from 58 to 71 [Ce to Lu]

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SOLUTION :LANTHANIDES.
Discussion
3514.

Select the word/words from the given list required to complete the following statements. Use one word only once and do not copy the complete statement. [ammonia, carbonate, ammonium, carbon dioxide, hydrogen, hydronium, hydroxide, salt, water, precipitate] (i) A solution M turns blue litmus red, therefore, it must contain (a) ____ ions. Another solution O turns red litmus blue, hence, it must contain (b)____ ions. (ii) When solutions M and O are mixed, the product will be ( c) _____ and (d) ______ . (iii) If a piece of magnesium was put into solution M (e) ___ gas would evolve.

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Solution :(i) (a) hydronium (b) hydroxide
(ii) ( C) salt (d) WATER
(iii) (E) HYDROGEN
Discussion
3515.

Select the stepe requried for the extraction of aluminium and sequence them. (1) froth flotation (2) chemical separation (3) electrolytic reduction (4) smelting (5) distillation under low pressure (6) electrolytic refining (7) Pulverisation (8) conversion of concentrated ore into oxide (9) crushing and grinding

Answer»

9 5 7 2 3 8 6 1
3 2 1 4 5 6 7 8
9 7 2 8 3 6
9 7 2 3 8 6

Solution :(i) Crushing and grinding
(ii) Pulverisation
(iii) Chemical separation
(iv) Conversion of CONCENTRATED ORE into oxide
(v) Electrolytic REDUCTION
(vi) Electrolytic refining
Discussion
3516.

Select the proper option for the following statements : Statement 1: Burning of magnesium ribbon in air is a redox reaction. Statement 2: Oxidation number of oxygen in its metal oxide is -1.

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STATEMENT 1 is CORRECT.
Statement 2 is INCORRECT.
Statement 1 is correct, but statement 2 is incorrect.
Statement 1 and statement 2 both are incorrect.

Solution :Statement 1 is correct, but statement 2 is incorrect.
Discussion
3517.

Select the odd one out and justify your choice: NH_(4)Cl,NaCl,KCl,KNO_(3)

Answer»

Solution :`NH_(4)CL` is odd one because it UNDERGOES hydrolysis, WHEREAS other SALTS do not hydrolyse in water.
Discussion
3518.

Select the odd one out and justify your choice: NaOH,KCl,NaHCO_(3),Na_(2)CO_(3)

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SOLUTION :KCL is odd one because it is a neutral SALT, whereas the other THREE are BASES.
Discussion
3519.

Select the odd one out and justify your choice: NaOH,CH_(3)COOH,C_(2)H_(5)OH,HCl

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SOLUTION :`C_(2)H_(5)OH` is odd one because the other CHEMICALS ionise in aqueous solution and CONDUCT electricity.
Discussion
3520.

Select the odd one out and justify your choice: HCl,NaCl,HNO_(3),CH_(3)COOH

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Solution :NACL is ODD ONE because it is a SALT, whereas the other chemicals are acids.
Discussion
3521.

Select the odd one out and justify your choice: Methyl orange, litmus, red cabbage extract, turmeric

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SOLUTION :METHYL orange is odd one because it is a synthetic INDICATOR, WHEREAS others are NATURAL indicators.
Discussion
3522.

Select the odd one out and justify your choice: NaCl,HCl,KCl,MgCl_(2)

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Solution :HCI is ODD ONE because it is an acid, whereas the other chemicals are SALTS.
Discussion
3523.

Select the odd one out and justify your choice: H_(2)SO_(4),HCl,H_(2)S,(COOH)_(2)

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SOLUTION :HCL is odd one because it is a monoprotic ACID, WHEREAS the other three are DIPROTIC acids.
Discussion
3524.

Select the monoprotic, diprotic and triprotic acids from the following: (i) Hydrochloric acid (ii) Sulphuric acid (iii) Phosphoric acid (iv) Acetic acid

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SOLUTION :HCL and `CH_(3)COOH` are monoprotic, `H_(2)SO_(4)` is diprotic, `H_(3)PO_(4)` is triprotic.
Discussion
3525.

Select the ion in each case , that would get slectively discharged from the aqueousmixture of ions listed below . Pb^(2+),Ag^(+) and Cu^(2+)

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SOLUTION :`AG^(+)`
Discussion
3526.

Select the ion in each case , that would get slectively discharged from the aqueousmixture of ions listed below . SO_(4)^(2-) , NO_(3)^(-) and OH^(-)

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SOLUTION :`OH^(-)`
Discussion
3527.

Select the hydrocarbons which are members of the same homologous series. Give the name of each series. C_(3)H_(8), C_(4)H_(10), C_(5)H_(10), C_(6)H_(10), C_(7)H_(12) and C_(8)H_(16).

Answer»

Solution :`C_(3)H_(8), C_(4)H_(10) to` Alkanes
`C_(5)H_(10), C_(8)H_(16) to` Alkenes
`C_(6)H_(10),C_(7)H_(12) to` Alkynes
Discussion
3528.

Select the formulae of alkanes, alkenes and alkynes from the following: CH_4, C_2H_4, C_2H_6, C_2H_2, C_3H_8, C_3H_4, C_4H_10, C_4H_8, C_4H_6, C_3H_6

Answer»

SOLUTION :(a) ALKANES : `CH_4, C_2H_6, C_3H_6, C_4H_10`
(b) Alkenes : `C_2H_4 , C_3H_6, C_4H_8`
(C) Alkynes: `C_2H_2, C_3H_4, C_4H_6`
Discussion
3529.

Select the formulae of acids, bases and salts from the following list: NaCl,NaHSO_(4),NaOH,H_(3)PO_(4),Na_(2)CO_(3),Ca(OH)_(2),CuSO_(4)*5H_(2)O,H_(2)SO_(4),KBr,NaHCO_(3),CaCO_(3)*10H_(2)O,KCl

Answer»

Solution :(i) ACIDS: `H_(3)PO_(4),H_(2)SO_(4)`
(ii) Bases: `NaOH,Na_(2)CO_(3),CA(OH)_(2),NaHCO_(3)`
(iii) Salts: `NaCl,NaHSO_(4),Na_(2)CO_(3),CuSO_(4)*5H_(2)O,KBR,NaHCO_(3),CaCO_(3)*10H_(2)O,KCl`
Discussion
3530.

Select the correct pair of properties of acetic acid.

Answer»

Smell-like VINEGAR, turns RED litmus to blue
Smell-like vinegar, turns blue litmus to red
Smell-like ORANGE, turns red litmus to red
Smell-like orange, turns red litmus to blue

SOLUTION :Smell-like vinegar, turns red litmus to red
Discussion
3531.

Select the acid which contains four hydrogen atoms in it.(a) Formic acid(b) Sulphuric acid(c) Nitric acid(d) Acetic acid

Answer»

FORMIC acid
Sulphuric acid
Nitric acid
Acetic acid

Solution :`CH_(3)COOH`
Discussion
3532.

Select saturated hydrocarbons from the following: C_(3)H_(6), C_(5)H_(10), C_(4)H_(10), C_(6)H_(14),C_(2)H_(4)

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SOLUTION :`C_(4)H_(10) and C_(6)H_(14)` are SATURATED hydrocarbons.
Discussion
3533.

Select saturated hydrocarbons from the followings : C_(3)H_(6),C_(5)H_(10), C_(4)H_(10),C_(6)H_(14),C_(2)H_(4)

Answer»


Answer :`C_(4)H_(10);C_(6)H_(14)`.
Discussion
3534.

Select saturated hydrocarbon from the following . C_3H_6 , C_5H_10, C_4H_10l C_2H_4, C_6H_14

Answer»

SOLUTION :HYDROCARBONS having only single bond between the carbon atoms are called saturated hydrocarbon. ALKANES are saturated hydrocarbons having general molecular formula `C_n H 2_n + 2` where `n = 1, 2, 3,…. :. C_4H_10` and `C_6 H_14` are satruated hydrocarbons.
Discussion
3535.

Select odd one out which does not fit as required and justify your answer Si, S, P, C "" Electrical conductivity

Answer»

SOLUTION :C is odd ONE because it conducts ELECTRICITY, whereas the other three do not.
Discussion
3536.

Select odd one out which does not fit as required and justify your answer Na, Cu, Mg, Hg ""Solid state

Answer»

Solution :HG is odd one because it is a liquid, WHEREAS the others are SOLID.
Discussion
3537.

Select odd one out which does not fit as required and justify your answer MgO, CaO, K_2O, P_2 O_5 "" Basic nature

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SOLUTION :`P_2 O_5` is odd one because it is acidic OXIDE, WHEREAS the OTHERS are BASIC.
Discussion
3538.

Select odd one out which does not fit as required and justify your answer K, Zn, Cu, AI "" Reaction with water

Answer»

SOLUTION :K is odd ONE because it reacts with WATER, WHEREAS others do not.
Discussion
3539.

Select odd one out which does not fit as required and justify your answer H, Li, Na, K "" Metallic nature

Answer»

Solution :H is ODD one because it is a nonmetal, WHEREAS the others are METAL.
Discussion
3540.

Select odd one out which does not fit as required and justify your answer H, F, CI, Br "" Gaseous state

Answer»

SOLUTION :BR is odd one because it exists as liquid, whereas OTHERS exist as GAS.
Discussion
3541.

Select odd one out which does not fit as required and justify your answer Fe, Zn, Cu, Al "" Reaction with dil. HCI

Answer»

Solution :Cu is odd ONE because it does not liberate hydrogen from DILUTE HCI.
Discussion
3542.

Select odd one out which does not fit as required and justify your answer Fe, Zn, Mg, Au "" Corrosion

Answer»

SOLUTION :Fe is odd ONE because it undergoes CORROSION, whereas the other THREE do not.
Discussion
3543.

Select odd one out which does not fit as required and justify your answer AI, Mg, Ca, Hg "" Isolation

Answer»

Solution :Hg is odd one because it is ISOLATED by HEATING its sulphide ore, WHEREAS the others are isolated by electrolytic reduction of their FUSED salts.
Discussion
3544.

Select odd one out from the following list of compounds.CH_4, C_2H_4, C_2H_6, C_3h_8

Answer»

Solution :`C_2H_4` ODD ONE because it is an alkene while the OTHERS are ALKANES.
Discussion
3545.

Select odd one out in the CH_4, C_3H_8, C_2H_4, C_2H_6, C_4H_10

Answer»

SOLUTION :`C_2H_4`
Discussion
3546.

Select odd one out in the CH_4, C_2H_4, C_3H_6, C_4H_8

Answer»

SOLUTION :`CH_4`
Discussion
3547.

Select odd one out in the C_2H_2, C_3H_4, C_3H_8, C_4H_6

Answer»

SOLUTION :`C_3H_8`
Discussion
3548.

Select odd one out from the following list of compounds.Formic acid, Nitric acid, Acetic acid, Propanoic acid.

Answer»

Solution :NITRIC acid is ADD one because it is a MINERAL acid, whereas the other three are CARBOXYLIC acids.
Discussion
3549.

Select odd one out from the following list of compounds.CH_3COOH, C_2H_5OH , CH_3OH, C_3H_7OH

Answer»

SOLUTION :`CH_3COOH ` is odd ONE because it is a CARBOXYLIC acid, WHEREAS the others are alcohols.
Discussion
3550.

Select odd one out from the following list of compounds.CH_3COOH , C_2H_4, C_3H_6, C_4H_8

Answer»

Solution :` CH_3COOH`is odd one because it is a CARBOXYLIC ACID, whereas the OTHERS are hydrocarbons.
Discussion