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2501.

Common salt increases in weight on long standing. Justify with an appropriate reason.

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Solution :(i) IMPURITIES present in common salt
(ii) NATURE of the impurities present in common salt
(iii) EFFECT of nature of the impurities on the INCREASE in weight
Discussion
2502.

Comment upon the following: rigidity, compressibility, fluidity, filling as gas container, shape, kinetic energyand density.

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Solution :Rigidity: The tendency of matter to maintain its shape when subjected to outside force.
Compressibililty: The propeerty of matter by which the particles of matter can be brought nearer, THEREBY reducing the VOLUME, by an external force.
Gases are highly compressible.
Fluidity: The PROPERTY ofthe particles of matter to flow. Solides have no fluidity. Liquids flow from a higher level to a lower level. Gases flow in all directions.
Filling a gas CONTAINER: The particles of gas vibrate randomly in all directions. The intramolecular force in negligible. So the gas can be filled in a container.
Shape: Solids have definite shape. Liquids and gases have no shape. They take the shape fo the container.
Kinetic ENERGY: The energy possessed by the particles of matter due to theri motion iscalled the kinetic energy. The particles of gases have the highest kinetic energy.
Density : The mass per unit volume of a substance is called density. The density of solids is highest compared to that of liquids and gases.
Discussion
2503.

Comment on the following statements. (a) Evaporation produces cooling. (b) Rate of evaporation of an aqueous solution decreases with increases with increase in humidity . (c) Sponge though compressible is a solid.

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Solution :(a) As a liquid changes into vapours during EVAPORATION, it NEEDS some energy which it takes from the surroundings. Since the temperature of the surroundings gets lowered, cooling is THEREFORE, caused.
(b) Increase in humidity results inincrease in moisture in the atmosphere. As a result, water has less tendency to change into the vapours and rate of evaporation decreases.
(c ) SPONGE is basically a solid. However, it has very fine holes which are called pin holes. Air gets trapped in these holes and the size of the sponge somewhat increases. On COMPRESSING, air escapes from the pores or holes and the size of the sponge decreses.
Discussion
2504.

Comment upon the following: Rigidity

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Solution :* Rigidity : It is the property of matter of resist the change of its shape.
* Compressibility : It is the property of matter in which its VOLUME is decreased by applying force.
* Fluidity : It is the ABILITY of matter to flow.
* Filling a GAS container : On filling a gas takes the shape of the container.
* Shape : Having definite BOUNDARIES.
* Kinetic energy : It is the energy possessed by the particles of matter due to its motion
* Density : It is the RATIO of mass with per unit volume
Discussion
2505.

combdryhair . Doesthe combthenattractsmallpiecesof paper ?

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SOLUTION :Thecomb ATTRACTS smallpiecesof PAPER.
Discussion
2506.

{:("Column I","Column II"),(1."Triads",(a)"Newlands"),(2."Alkali metal",(b)"Calcium"),(3."Law of octaves",(c)"Henry Moseley"),(4."Alkaline earth metal",(d)"Sodium"),(5."Modern Periodic Law",(e)"Dobereiner"):}

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ANSWER :1 - (E), 2 - (d), 3 - (a), 4 - (b), 5 - (c)
Discussion
2507.

Colourless gas formed by treating phosphorus with NaOH is phosphine.

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SOLUTION :N/A
Discussion
2508.

Colloidal particles can pass through ordinary filter papers.

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ANSWER :T
Discussion
2509.

Colloid is stable, while suspension is unstable.

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ANSWER :1
Discussion
2510.

Colloid is a _____ .

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homogeneous MIXTURE
heterogeneous and TRANSPARENT mixture
heterogeneous mixture in which component PARTICLES can be seen by NAKED eyes
heterogeneous mixture in which component particles cannot be seen by naked eyes

Answer :A::B::C::D
Discussion
2511.

Collect the following samples from the science laboratory- Hydrochloric acid, sulphate acid and Nitric acid, Sodium hydroxide, Potassium hydroxide. Take 2 ml of each solution in a test tube and test with a litmust paper and indicators phenolphthaleia nad Methyl orange. Tabulate your observations.

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SOLUTION :
Discussion
2512.

Coke is obtained by the destructive distillation of coal .But, coke is considered to be the purer form of carbon than coal Give a reason.

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Solution :Coal contains appreciable proportion of sulphur ' and nitrogen as it is formed by the degradation of dead ORGANIC matter. During destructive distillation of coal, sulphur and nitrogen are removed and COKE is OBTAINED which is a purer FORM of CARBON.
Discussion
2513.

Coal has a major role to play in the production of steel.Explain the role of coal.

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SOLUTION :(i) composition of STEEL
(ii) compound formed with MAJOR CONSTITUENT of coal andthat of major constituent of steel
(iii) effect of FORMATIONOF this compound on steel
Discussion
2514.

Coal gas mainly consites of

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METHANE `CO,H_2`
`"Propane" CO_2 H_2`
`"methane" CO H_2O`
methane `CO_2,H_2`

SOLUTION :The constituents of COAL GAS are methane, carbon MONOXIDE and hydrogen.
Discussion
2515.

Co_(2) can be easily liquefied and even solidified because_________ .

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It has weak FORCE of ATTRACTION
It has comparatively more force of attraction than other gases.
It has more intermolecular space.
It is present in atmosphere.

ANSWER :B
Discussion
2516.

Co stands for ............ while Co stands for ......... respectively.

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SOLUTION : COBALT, CARBON MONOXIDE
Discussion
2517.

CNG is a better automobile fuel when comparedto petrol and diesel. Give reasons.

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Solution :In CNG, the major COMPONENT is methane. Since the calorific value is more and the products FORMED as a result of combustion are less polluting agents When COMPARED with PETROL and diesehit is pre ferred. Petrol and diesel are mixtures of hydrocar- bons Where INCOMPLETE combustion takes place forming carbon monoxide which cases air pollution. Moreover in petrol and diesel sulphur and nitrogen are present which form corresponding oxides. These oxides cause air pollution. Further CNG undergo rapid combustion due to its low ignition temperature.
Discussion
2518.

Closed chain hydrocarbons which do not resemble aliphatic hydrocarbons in their chemical behaviour are called "_________"

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SOLUTION :AROMATIC HYDROCARBONS
Discussion
2519.

Classify thhe pure substance on the basis of chemical composition.

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SOLUTION :
Discussion
2520.

Classify the types of mixtures,

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SOLUTION :
Discussion
2521.

Classify the substances given in Figure into elements and compounds.

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Solution :Elements : Cu, Zn, Hg, DIAMOND.
Compounds : `H_(2)O, CaCO_(3), O_(2), F_(2)`
Note : Sand, NaCl (aq) and WOOD are the examples of MIXTURES.
Discussion
2522.

Classify the following into osmosis/diffusion. (a) Swelling up of a raisin on keeping in water. (b) Spreading of virus on sneezing. (c) Earthworm dying on coming in contact with common salt. (d) Shrinking of grapes kept inthick sugar syrup. (e) Preserving pickles in salt (f) Spreading of smell of cake being baked through out the house. (g) Aquatic animals using oxygen dissolved in water during respiration.

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SOLUTION :(a) Osmosis (B) Diffusion ( C) Osmosis (d) Osmosis (e ) Osmosis (f) Diffusion (G) Diffusion.
Discussion
2523.

Classify the following into elements, compounds and mixtures : (a) Sodium (b) Soil ( c) Sugar solution (d) Silver (e) Calcium carbonate (f) Tin (g) Silicon (h) Coal (i) Air (j) Soap (k) Methane (1) Carbon dioxide (m) Blood

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SOLUTION :Elements : Sodium, Silver, Tin, Silicon.
Compounds : Calcium CARBONATE, Soap, Methane, CARBON dioxide.
Mixtures : Soil, Sugar solution, Coal, AIR, BLOOD.
Discussion
2524.

Classify the following into elements, compounds and mixtures (a) sodium (b) soil, (c ) sugar solution (d) silver (e ) calcium carbonate (f) soap (g) tin (h) silicon (i) coal

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Solution :`{:("Elements","Compounds","Mixtures"),("SODIUM","Calcium CARBONATE","Soil"),("Silver","Methane","SUGAR"),("Tin","Carbon DIOXIDE","Coal"),("Silicon",,"Air"),(,,"Soap"),(,,"Blood"):}`
Discussion
2525.

Classify the following compounds as ionic and covalent. (Hint:- electronegativity C = 2.55, 0=3..44 CI = 3.6 H=2.20, Na = 0.93 NaCl

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ANSWER :NACL - IONIC
Discussion
2526.

Classify the following compounds as ionic and covalent. (Hint:- electronegativity C = 2.55, 0=3..44 CI = 3.6 H=2.20, Na = 0.93 HCl

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ANSWER :HCL - COVALENT
Discussion
2527.

Classify the following compounds as ionic and covalent. (Hint:- electronegativity C = 2.55, 0=3..44 CI = 3.6 H=2.20, Na = 0.93 NaH

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ANSWER :NAH - IONIC
Discussion
2528.

Classify the following compounds as ionic and covalent. (Hint:- electronegativity C = 2.55, 0=3..44 CI = 3.6 H=2.20, Na = 0.93 CO_2

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ANSWER :`CO_2` -COVALENT
Discussion
2529.

Classify the following as pure substances or mixtures. Separate the pure substances into elements, compounds and divide the mixtures into homogenous and heterogenous :(i) Air(ii)Milk(iii) Graphite (iv) Gasoline (v) Diamond (vi) Tap water (vii) Distilled water (viii) Oxygen (ix) Brass (x) 22 Carat gold(xi) Steel(xii) Iron (xiii) Sodium chloride (xiv) Iodised table salt.

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Solution :`{:((i),"AIR",:,"Mixture (Homogeneous)"),((ii),"Milk",:,"Mixture (Homogeneous)"),((III),"Graphite",:,"Pure SUBSTANCE (Element)"),((iv),"Gasoline",:,"Mixture (Homogeneous)"),((v),"Diamond",:,"Pure substance (Element)"),((vi),"Tap water",:,"Mixture (Homogeneous)"),((vii),"Distilled water",:,"Pure substance (COMPOUND)"),((viii),"Oxygen",:,"Pure substance (Element)"),((ix),"Brass",:,"Mixture (Homogeneous)"),((x),"22 Carat gold",:,"Mixture (Homogeneous)"),((x i),"STEEL",:,"Mixture (Homogeneous)"),((x ii),"Iron",:,"Pure substance (Element)"),((x iii),"Sodium chloride",:,"Pure substance (Compound)"),((x iv),"Iodized table salt",:,"Mixture (Heterogeneous)"):}`
Discussion
2530.

Classify the following as physical or chemical properties. (a) The composition of a sample of steel is : 98% iron, 1.5% carbon and 0.5% other elements. (b) Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas. (c) Metallic sodium is soft enough to be cut with a knife. (d) Most metal oxidesform alkalis on interacting with water.

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SOLUTION :(a) PHYSICAL (B) CHEMICAL (C ) Physical(d) Chemical.
Discussion
2531.

Classify the following as physical and chemical changes. Give reason for your answer. (a) Burning of candle.(b) Melting of ice.(c ) Burning of petrol in an engine.(d) Change of colour of iron bar on strong heating(e) Churning of milk to get butter.

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Solution :(a) Chemical change :
(b) Physical change : When WATER formed as a result of melting of ice is cooled to `0^(@)C`,it changes back to ice.
(c ) Chemical change : Petrol is a mixture of different hydrocarbons. They undergo oxidation or combustion upon burning to FORM carbon dioxide and water vapours ALONG with heat energy. Therefore, it is a chemical change.
(d) Physical change : Iron bar regains its colour on cooling.
(e) Physical change : There is only a change of physical state and no NEW SUBSTANCE is formed.
Discussion
2532.

Classify the following as physical and chemical changes.(i)Conversion of milk into curd (ii) Burning of magnesium ribbon in air (iii) Rusting of iron nails(iv) Dissolving salt in water (v) Burning of cool(vi) Electrolysis of sodium chloride solution by passing current (vii) Crystallisation of copper sulphate.

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Solution :(i) CHEMICAL change(ii) Chemical change(iii) Chemical change(IV) PHYSICAL change(V) Chemical change(vi) Chemical change(vii) Physical change.
Discussion
2533.

Classify each of the following as a homogeneous or heterogeneous mixtures : Soda water, wood, air, soil, vinegar, filtered tea.

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Solution :Homogeneous MIXTURES : SODA water, air, vinegar, FILTERED tea.
HETEROGENEOUS mixtures : Wood, soil.
Discussion
2534.

Classify each of the following as a homogeneous or heterogeneous mixture. soda water, wood , air, soil , vinegar, filtered tea.

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Solution :HOMOGENEOUS mixtures : Soda water, air, vinegar, filtered TEA
Heterogeneous mixtures : WOOD, soil
NOTE : PURE air is homogeneous mixture but Polluted air is heterogeneous mixture.
Discussion
2535.

Classify each of the following, as a physical or a chemical change. Give reasons. (a) Drying of a shirt in the sun. (b) Rising of hot air over a radiator. (c) Burning of kerosene in a lantern. (d) Change in the colour of black tea on adding lemon juice to it. (e) Churning of milk cream to get butter.

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Solution :(a) It is a physical change. Moisture or water drops PRESENT on the SHIRT will evaporate or change into vapours.
(b) It is a physical change. On cooling, the level of air over the radiator will fall.
(c ) It is a chemical change. The hydrocarbons present in kerosene will react chemically with OXYGEN to form new products.
(d) It is a chemical change. The acid present in lemon juice will react the constituents (E.g. CAFFEINE) present in black tea.
(e) It is a physical change. However, butter will not change to milk so easily.
Discussion
2536.

Classify colloids based on physical state of dispersed phase and dispersion medium.

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SOLUTION :
Discussion
2537.

Classify each fo the following on the basis of their automicity. (a)O_3 (b)P_4 (c)S_8

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SOLUTION :`{:(,(a)F_(2),(b)NO_(2),(C)N_(2)O,(d)C_(2)H_(6)),(,(e)P_(4),(f)H_(2)O_(2),(g)P_(4)O_(10),(h)O_(3)),(,(i)HCl,(j)CH_(4),(k)He,(L)Ag):}`
Discussion
2538.

Classifyeach of the Followingas ahomogenousor Heterogenousmixture ? Soda , Water, Wood , Air, Soil,Vinegar ,Filtered tea .

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SOLUTION :Homogeneous mixture :- SODA water, air VINEGAR and FILTERED tea.
Heterogeneous mixture :- Wood and SOIL.
Discussion
2539.

Classify as Chemical or PhysicalChanges of making fruit salad withrawfruits ?

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SOLUTION :PHYSICAL CHANGE
Discussion
2540.

Classify as Chemical or PhysicalChanges of Rusting of almirah ?

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SOLUTION :CHEMICAL CHANGE
Discussion
2541.

Classify as Chemical or PhysicalChanges of Passing of Electric current through waterandwater breakingdowm intohydrogen and oxygen gases?

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SOLUTION :CHEMICAL CHANGE
Discussion
2542.

Classify as Chemical or PhysicalChanges of Melting of Butter in a pan

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SOLUTION :PHYSICAL CHANGE
Discussion
2543.

Classify as Chemical or PhysicalChanges ofdissolving common salt in water?

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SOLUTION :PHYSICAL CHANGE
Discussion
2544.

Classify as Chemical or PhysicalChanges of Cutting of tress ?

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SOLUTION :PHYSICAL CHANGE
Discussion
2545.

Classify as Chemical or PhysicalChanges ofburning of paper and wood ?

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SOLUTION :CHEMICAL CHANGE
Discussion
2546.

Classify as Chemical or PhysicalChanges of Boiling of water to form Steam ?

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SOLUTION :PHYSICAL CHANGE
Discussion
2547.

Classify acids based on their sources and basicity.

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Solution :Acids are classified in different ways as follows:
Based on their sources:
(1) Organic acids: Acids present in plants and ANIMALS (living things) are organic acids. Example: `HCOOH, CH_(3)COOH`
(ii) Inorganic acids: Acids prepared from rocks and minerals are inorganic acids or mineral acids. Example: `HCl, HNO_(3). H_(2)SO_(4)`
Based on their Basicity
Monobasic Acid: Acid that contain only one replaceable hydrogen atom per molecule is called monobasic acid. It gives one hydrogen ion per molecule of the acid in solution.
Example: HCI, `HNO_3`
Dibasic Acid: An acid which gives two hydrogen IONS per molecule of the acid in solution. Example: `H_(2)SO_(4), H_(2)CO_(3)`
TRIBASIC Acid: An acid which gives THREE hydrogen ions per molecule of the acid in solution.
Example `H_(3)PO_(4)`.
Discussion
2548.

Cl + 1e^- rarr Cl^(1-) Which is the oxidising agent in this chemical reaction ?

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ANSWER :CHLORINE (CL)
Discussion
2549.

Cl + 1e^- rarr Cl^(1-) which atom is reduced ?

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ANSWER :CHLORINE
Discussion
2550.

Chromatography is based on the principle of ______

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ANSWER :ABSORPTIONS
Discussion