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1001.

Sudha tested the solubility of four salts X, Y, Z and T as different temperature and collected the following data. (Solubility refers to the amount in grams dissolved in 100 g of water to give a saturated solution.)Answer the following question from the table (i) Which salt has the highest and lowest solubility at 323 K ? (ii) A student prepared a saturated solution of X at 323 K and then added 25 g water to it. Water mass of X must be added to again make the solution saturated ? (iii) The solubility of which salt is least affected by increase in temperature ? (iv) What mass of 'T' would be required to make saturated solution in 200 g of water at 290 K ?

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Solution :(I) At 323 K, SALT Y has the highest solubility in water while salt Z has the lowest solubility
(ii) By definition of saturated solution,
100 G of water at 323 K contain salt = 40 g
125 g of water at 323 K contain salt = `((40 g))/((100g)) xx (125 g) = 50 g`
`therefore` Mass of salt to be added to make the solution again saturated = (50 - 40) = 10 g
(iii) The data SHOWS that the solubility of the salt Y is least affected with increase in temperature.
(iv) At 290 K, mass of T required to make the saturated in 200 g of water = `((25 g))/((100g)) xx (200g)50 g`
Discussion
1002.

Sudden change in the temperature of water in the river harms

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MAN
cattle
plants
FISHES

ANSWER :D
Discussion
1003.

Study temperature -time graph given below: The graph shows heating of ice form -10^(@)C to water at 100^(@)C. Identify the part of the graph which represents the change of state on heating. During change of state where does the absorbed heat energy go?

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Solution :Parts BC and DE of the GRAPH represents the change of state on HEATING.
The heat energy SUPPLIED during the change of state is used to overcome the force of attraction between the particles or matter. This heat is known as latent heat. [The heat energy is STORED in water at`0^(@)C` in the form of latent heat of fusion and is stored in steam at`100^(@)C` in the form of latent heat of vaporisation.]
Discussion
1004.

Stationary orbit

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Solution :While MOVING AROUND the nucleus in an orbit of an ATOM, ELECTRON does not LOSE any energy. Such an orbilt is known as stationmary orblt.
Discussion
1005.

States the differences between solid and gasesous states on the basis of 1 intermolecular space and 2. compressibility.

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SOLUTION :
Discussion
1006.

Statement : Elements in a group generally posses similar properties but elements along a period have different properties. Reason : The difference in electronic configuration makes the element differ in their chemical proporties along a period.

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Statement is TRUE and reason explains the statement.
Statement is FALSE but the reason is correct

Answer :A
Discussion
1007.

State whether the following statements are true or false : (a) Thomson proposed that the nucleus of an atom contains protons and neutrons (b) he cathode rays obtained from all the gases consists of negatively charged particles called electrons (c) The anode rays obtained from all the gases consist of positively charged particles called protons.

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ANSWER :(a) FALSE (B) TRUE (C) False
Discussion
1008.

State the valence electrons in graphite.

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2
3
5
4

Answer :D
Discussion
1009.

State the uses of isotopes.

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Solution :Uses of ISOTOPES are as FOLLOWS:
(1)An ISOTOPE of uranium is used as a fuel in nuclear reactors.
(2) An isotope to cobalt is used in the treatment of cancer.
(3)) An isotope of iodine is used in the treatment of goltre.
[An isotope of phosphorus is used in the treatment of leukemia. An isotope of sodiumn is used to detect the presence of BLOOD clots.]
Discussion
1010.

State the reactions the take place at the cathode and anode during the process of electrolytic reduction of alumina.

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SOLUTION :N/A
Discussion
1011.

State the properties of colloid solution.

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Solution :The properties of colloid solution are as follows:
(1) It is a heterogeneous mixture.
(2) The size of particles is too small to be seen by an unaided EYE.
(3) The particles of collid scatter a beam of light.
(4) The particles do not settle down when LEFT UNDISTURBED. So it is stable.
Discussion
1012.

State the properties of a suspension.

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Solution :The properties of a suspension are as follows:
(1) It is a HETEROGENEOUS MIXTURE.
(2) The size of particles are more than 100 nm. They are visible by an unaided EYE.
(3) The particles of suspension scatter a beam of hight.
(4) The solute particles settle down when a suspension is left undisturbed. So, it is UNSTABLE.
Discussion
1013.

State the properties of a solution.

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Solution :The properties of a solution are as follows:
(1) It is a homogeneous mixture.
(2) The SIZE of particles are less than 1 NM and cannot be seen by an unaided eye or a POWERFUL microscope.
(3) The solution does not scatter BEAM of LIGHT.
(4) It is stable.
Discussion
1014.

State the postulates of Dalton.s atomic theory.

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Solution :The postulates of Dalton.s atomic theory:
(1) All matter is made of very tiny PARTICLES called atoms.
(2) Atoms are indivisible particles which cannot be created or destroyed in a chemical reaction.
(3) Atoms of given element are identical in mass and chemical properties.
(4) Aloms of different ELEMENTS have different masses and chemical properties.
(5) Atom combine in the ratio of small WHOLE numbers to form compounds.
(6) The relative number and kinds of atoms are constant in a given compound.
Discussion
1015.

State the pair of isobar elements.

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`""_(20)^(40)Ca, " "_(17)^(35)`Cl
`""_(18)^(20)Ca, " "_(19)^(20)`Cl
`""_(8)^(16)Ca, " "_(8)^(18)`Cl
`""_(7)^(19)Ca, " "_(7)^(13)`Cl

Answer :A::B::C
Discussion
1016.

State the physical nature of matter.

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Solution :Matter CONSISTS of PARTICLES which are EXTREMELY SMALL.
Discussion
1017.

State the mole proportion of 12 g magnesium and 16 g sulphur.

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3:4
4:3
1:1
1:2

Solution :MOLE of 12 g MG = `(12)/(24)` = 0.5
Mole of 16g S = `(16)/(32)` = 0.5
Discussion
1018.

State the law of multiple proportion.

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SOLUTION :When two elements combine together to FORM more than one COMPOUND, the mass of two elements combines with a fixed mass in SIMPLE ratio.
Discussion
1019.

State the law of mass action.

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Discussion
1020.

State the law of constant proportion.

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Solution :The law of CONSTANT proportion states that in a chemical SUBSTANCE the elements are ALWAYS present in definite proportion by mass.
Discussion
1021.

State the Gay Lussac's law of combining volumes, explain with an illustration.

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SOLUTION :Whenever gases REACT together, the volumes of the reacting gases and the products bear a simple whole number ratio, providedall the volumes are measured under similar conditions of temperature and pressure .
Steps:
a.HYDROGEN combines with oxygen to from water
b. `H_(2) + 1//2 O_(2) rarr H_(2)O ""` (Skeletal equation)
c.`2H_(2(g)) + O_(2(g)) rarr 2H_(2)O_((g)) ""` (balanced equation)
(2 volumes) + (1 volume) `""`(2 volumes)
`2:1:2`
TWO volumes of hydrogen react with ONE volume of oxygen to from two volumes of water vapour that is the ratio by volume, which gases bears is 2 : 1 : 2 , which is a simple whole number ratio.
Discussion
1022.

State the electronic configuration of ""_(17)^(35)Cl.

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2,7
2,8,8,7
2,8,7
2,7,8

Answer :B
Discussion
1023.

State the effect of heat on diffusion.

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SOLUTION :On HEATING, DIFFUSION BECOMES FASTER.
Discussion
1024.

State the correct electronlc strueture of Mg^(2+) from the following :

Answer»





SOLUTION :
Discussion
1025.

State the atomicity of ozone, sulphur, phosphorus and helium respectively.

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<P>8, 3, 4, 1
1, 3, 4, 8
4, 1, 8, 3
3, 8, 4, 1

Solution :The ATOMICITY of `O_(3), S_(8), P_(4)` and He are 3, 8, 4 and 1 respectively.
Discussion
1026.

State one similarity and one dissimilarity between protons and neutrons.

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Solution :Similarity: Protons and NEUTRONS are present in the NUCLEUS of an atom.
Dissimilarity: Protons possess a unit positive CHARGE. Neutrons carry no charge.
Discussion
1027.

State Le Chatelier's principle and apply it to the following equilibria : (i) 2NH_(3(g)) hArr N_(2(g))+3H_(2(g))-" Heat" (ii) 2NO_((g)) hArr N_(2(g))+O_(2(g))+" Heat"

Answer»
Discussion
1028.

State law of mass action. Apply it to the following equilibria : (a) 2SO_(2(g))+O_(2(g)) hArr 2SO_(3(g)) (b) 3Fe((s))+4H_(2)O((g)) hArr Fe_(3)O_(4(s))+4H_(2)((g))

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Discussion
1029.

State Le Chatelier's principle.

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Discussion
1030.

State any five feastures of modern periodic table.

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Solution :All the elements are arranged in the increasing order of their atomic number
The horizontal rows are called PERIODS. There are seven periods in the PERIODIC table.
The elements are placed in periods based on the number of shells in their atoms
Verticall columns in the periodic table starting from top to BOTTOM are called groups. There are 18 groups in the periodic table.
Based on the physical and chemical PROPERTIES of elements, they are ground into various families.
Discussion
1031.

State and explain the law of mass action. Apply it to the following equilibria : (i) H_(2(g))+I_(2(g)) hArr 2HI((g)) (ii) NH_(4)HS_((s)) hArr NH_(3(g))+H_(2)S((g)) (iii) 2SO_(2(g))+O_(2(g)) hArr 2SO_(3(g))

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Discussion
1032.

State and explain the postulates of the collision theory of reaction rates.

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Discussion
1033.

Sponge, though compressible, is a solid. Comment.

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SOLUTION :SPONGE, being porous, is compresible. It pssesses most the other PROPERTIES of a SOLID. Therefore, sponge is a solid.
Discussion
1034.

Spectral line given by an atom is a kind of signature of the respective atom. Commnet of this statement.

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Solution :(i) calcualtion of energy of ELECTRONS in `He^(+)` and `LI^(+2)` IONS.
(ii) `4:9`
Discussion
1035.

(a) What is the name given to the liquids which dissolve in a liquid ?(b ) What is the name given to the liquid which contains in it some suspended particles ?

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SOLUTION :(a) The liquids are known as solvents
(b)The LIQUID is known as dispersion medium or DISPERSING medium.
Discussion
1036.

Some of the alpha-rays deflect in acute and obtuse angles due to the presence of the ________in the centre of the atom.

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SOLUTION :POSITIVE CHARGE
Discussion
1037.

Some metal oxides dissolve in water to produce alkalis. Is the process a chemical change ?

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SOLUTION :YES, it is a CHEMICAL CHANGE .
Discussion
1038.

Some metals can be hammered to form very thin sheets .

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ANSWER :T
Discussion
1039.

Some amount of Glauber's salt, hydrated magnesium chloride and hydrated calcium chloride are separately is kept in three containers. What will you observe, if blue coloured cobalt chloride is introduced in the three containers ? Explain with a reason.

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Solution :(i) comparison of the nature of THREE GIVEN hydrated SALTS
(ii) effect of the nature of three hydrated salts on cobalt chloride
(iii) change in colour of cobalt chloride
Discussion
1040.

Solution which as uniform composition throughout is called __________.

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ANSWER :HOMOGENEOUS SOLUTION
Discussion
1041.

Solids possess very high kinetic energy

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SOLUTION :Correct statement: GASES possess very HIGH KINETIC ENERGY.
Discussion
1042.

Solids generally undergo melting on heating. But only certain specific solids like naphthalene camphor undergo sublimation. Give a reason.

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Solution :(i) COMPARISION of vapour pressure of solids which undergo sublimation to normal solids
(II) CAUSE of sublimation
(iii) requisite of vapour pressure of SOLID to SUBLIME
Discussion
1043.

Solid substances have more density. And are non compressible.

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Solution :There exists INTERMOLECULAR FORCES between the atom or molecular force between the COMPONENTS of solids is maximum and so their components of solids is maximum and so their component particles are placed together tightly. Thus, due to more number of molecules PRESENT in unit volume, number of molecules present in unit volume density of the solid substance is more and it is NON compressible.
Discussion
1044.

Solid state and Liquid State

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SOLUTION :
Discussion
1045.

Solid carbon dioxide is called ....................

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SOLUTION :DRY ICE
Discussion
1046.

Soil provides ........ for the growth of plants .

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SOLUTION :NUTRIENTS
Discussion
1047.

Sodium having atomie number 11, ready to ............electron/electrons to attain the linearest Noble gas electronic configuration.

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GAIN ONE
gain TWO
LOSE one
lose two

Answer :C
Discussion
1048.

Sodium cannot be preserved in water. However, sodium amalgan can be kept in water. Justify.

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Solution :(i) PREDICTING the ORDER of VAPOUR pressure of given COMPOUNDS
(ii) changes occuring when METAL is preserved in water
(iii) properties of sodium in amalgam
(iv) effect of water on sodium amalgam
Discussion
1049.

Snehal accidently dropped a tin of sugar on the floor. She collected sugar. Some dust particles also mixed with sugar. She was worried about cleaning sugar. Her daughter Heena studying in Std. IX told her mother not to worry. She made the sugar free of dust. (1) Which process did Heena use to purify sugar ? (2) What value of Heena is seen here ?

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Solution :(1) HEENA dissolved sugar in water. She filtered it and REMOVED dust particles. The FILTRATE contained sugar solution in water. She recovered sugar by CRYSTALLISATION METHOD.
(2) Heena showed a helping nature, caring and putting her knowledge in practice.
Discussion
1050.

Smoke and fog both are ..............

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ANSWER :AEROSOLS
Discussion