1214 + Interview Questions in Chemistry in Class 8 Page 23 InterviewSolution

1101.	An atom of an element has one electron in the valence shell and the two consecutive inner shells have 8 electrons each. Find the atomic number of that element. Write the electronic configruation of preceding nad succeding elements.
Answer» Solution :K shell `to 2` ELECTRONS L shell `to ` electrons M shell `to 8` electrons N shell `to 1` Atomic number =2+8+8+1=19 PRECEDING element is Ar and electronic configuration is 2,8,8, succeeding ELMENT is Ca and its electronic configuration is 2,8,8,2.

Discussion

1102.	An atom of an element has mass number 31. It has 16 neutrons. The valence shell and the number of valence electrons, respectively, could be
Answer» M SHELL and 6 electrons M shell and 5 electrons N shell and 5 electrons L shell and 6 electrons Solution :Mass number =31 . Number of neutrons =16 ATOMIC number =31-16=15 Electronic ARRANGEMENT is 2,8,5, 'M' shell is valence shell and and there are 5 electrons in the valence shell. 6

Discussion

1103.	An atom of an element has 4th shell as the valence shell. The difference between electrons present in L and M and N shells are 1 and 0 respectively. Find the atomic number of an element.
Answer» Solution :(i) Number of electrons PRESENT in K and L SHELL. (ii) Number of electrons in Kande M and N shell. (iii) Writing electronic CONFIGURATION.

Discussion

1104.	An atom is considered to be electrically
Answer» positive negative neutral positive or negative Answer :C

Discussion

1105.	Amphoteric oxides are ……………….. Oxides that show both acidic and basic properties.
Answer» SOLUTION :METALLIC

Discussion

1106.	Amount of solutes A,B,C,D and E in 1500 g of water at 25^(@)C , 50^(@)C and 75^(@)C in their saturated solutions are given below {:(,25^(@)C,50^(@)C,75^(@)C),(A,235 g , 280 g ,240 g ),(B,180 g , 190 g , 220 g),(C,160g ,170 g ,180g ),(D,175 g , 220 g , 200 g):} Arrange the solutes in the increasing order of the amount of solutes that crystallises out by cooling from 75^(@)Cto 25^(@)C
Answer» ABDC ACDB CABD ACBD Solution :AMOUNT of solutes A,B,C and D that crystallizes out are 5g , 40G, 20G and 25g respectively.

Discussion

1107.	Amount of solutes A,B and C in 500 g of water at 30^(@)C ,60^(@)C , 100^(@)Cin their saturated solutions are given below. {:(,30^(@)C,60^(@)C,100^(@)C),(A,140 g, 135 g,131 g),(B,160 g, 175 g, 182 g ),(C,152 g, 170 g, 161 g):} When the hot saturated solutions of A, B and C are cooled slowly, identify the order in which they crystallize out of a solution. Give reason in support of your answer.
Answer» Solution :(i) comparision of changes in soubilities with change in temperature. (ii) Comparision of change is solubilities with decrease in temperature from `100^(0)C` to `30^(0)C . (III) Effect of COOLING on nature of the solutions of A , B, C respectively. (iv) Relation between extent of SOLUBILITY and crystallization.

Discussion

1108.	Among white phosphorous and red phosphorous which is more preferable for use in match sticks? Give reason in support of your answer
Answer» Solution :(i) COMPARISON of property of red and white phosphorous. (ii) Comparison of REACTIVITY ofwhite phosphorus and red phosphorus. (III) Comparison of IGNITION TEMPERATURES of white phosphorus and red phosphorus

Discussion

1109.	Among the following oxides which one is converted to metal by treated with hydrogen ?
Answer» `Al_(2)O_(3)` `ZnO` `CuO` `BaO` Solution :In metals, which have lesser affinity TOWARDS oxygen , their oxides can be REDUCED by hydrogens. Among the given metals , COPPER has LESS affinity towards oxygen. Hence its oxide can be reduced by hydrogen .

Discussion

1110.	Among all the layers of atmosphere the layer with the highest temperature is________.
Answer» SOLUTION :theremosphere

Discussion

1111.	Ammonium chloride on reaction with quick lime gives a gasX w hich turns red litmus blue.Excess ofXand greenish yellow gas are taken in containerAand excess ofgreenish yellow gas andX are taken in container B which on reaction gives difFerent sets ofproducts.When moist litmus paper is introduced into the jars, it turned to red in jarB . Identify the reactions involved and give equations.
Answer» Solution :(i) IDENTIFICATION of product formed in the reaction of `NH_4Cl` and CaO. (II) Reaction between X and the greenish yellow gas in container A. (III) Reaction between X and the greenish yellow gas in container B. (iv) Comparison of nature of the products formed in the. two containers,A and B. (v) Effect of nature of products on litmus paper

Discussion

1112.	Ammonium chloride can be separated from salt by .................. (evaporation/ sublimation)
Answer» SOLUTION :SUBLIMATION

Discussion

1113.	Aluminium reacts strongly with cold water to form hydroxide.
Answer» ANSWER :F

Discussion

1114.	Aluminium oxide is following type of an oxide.
Answer» basic acidic amphoteric neutral Answer :C

Discussion

1115.	Aluminiumfoil can be made from aluminium by using
Answer» its THERMAL and electrical CONDUCTIVITY. its MALLEABLE PROPERTY. its sonorous property. All the above Answer :B::C

Discussion

1116.	Alloys are homogeneous mixtures.
Answer» ANSWER :1

Discussion

1117.	......................allotropes of carbon do not have a definite geometric shape.
Answer» ANSWER : AMORPHOUS

Discussion

1118.	Allotropes have the same.....................properties and different.....................
Answer» ANSWER :CHEMICAL; PHYSICAL

Discussion

1119.	All matter is made up of tiny particles called ______ or ______
Answer» SOLUTION :ATOMS, MOLECULES

Discussion

1120.	All atoms of an element are identical.
Answer» ANSWER :T

Discussion

1121.	Air is a mixture.
Answer» ANSWER :1

Discussion

1122.	Ag+CuSO_4toCu+AgSO_4 Is this reaction possible ? Explain.
Answer» SOLUTION :CU is more ELECTROPOSITIVE than AG

Discussion

1123.	Addition of potassium nitrate to ice results in
Answer» increase in MELTING point. decrease in melting point. CHANGE in COLOUR of ice. Both (1) and (3) Answer :B::C

Discussion

1124.	According to Thomson
Answer» Negative charge of an atom is uniformly distributed throughout the atom. the volume OCCUPIED by positive charge is LESS than that occupied by the negative charge. electrons are embebbed in the positive charge which is spread uniformly. None of the above Answer :C

Discussion

1125.	According to the kinetic molecular theory, explain the following. (a) Density of a solid is the highest. (b) Gases are highly compressible whereas solids are incompressible. (c ) Liquids and gases are fluids whereas solids are rigid.
Answer» SOLUTION :(i) INTERMOLECULAR FORCE of attraction. (II) Intermolecular SPACES.

Discussion

1126.	According to Rutherford electrons revolve around the nucleus in ______.
Answer» SOLUTION :CERTAIN PATHS

Discussion

1127.	According to Rutherford ______ force of nucleus is balanced by the high velcoity of revolving electrons.
Answer» SOLUTION :ELECTROSTATIC

Discussion

1128.	According to Rutherford , electrons move around thenucleus in circular paths. How did the correlate this with the stability of an atom.
Answer» SOLUTION :(i) Forces existing between ELECTRONS and PROTONS (ii) Forces ACTING to counter balance columbic forces.

Discussion

1129.	According to law of conservation of mass:
Answer» REACTANTS mass = products mass GASES are lighter than solids kinetic energy changes with HEAT reactants + oxygen = products Solution :reactants mass = products mass

Discussion

1130.	According to Bohr's theory , the electrons revolve round the nucleus in definite paths called orbits . Do the electrons revolve round with same speed in all orbits? Justify.
Answer» Solution :The electrons revolve round the nucleus at high speed in the ORBITS in ORDER to counterbalance the nuclear forces of attraction. As nuclear force of attraction decreases with increase in distance from the nucleus , the nuclear force fo attraction on the electrons decreases. Therefore, electron revolves round with lesser velocity to overcome lesser nuclear force of attraction . THUS, hte veolcity of electron in orbits decreases in the order `K gt L gt M gt N`

Discussion

1131.	According to Bohr's atomic model, electrons revolve in ______ orbits.
Answer» SOLUTION :CIRCULAR

Discussion

1132.	Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?
Answer» ANSWER :Ramesh's BEAKER will get heated in a shorter time as the outermost part of the flame is the HOTTEST whereas the part near the wick in the yellow part of the candle flame, where Abida kept the beaker is the LEAST hot.

Discussion

1133.	A_2X is comprised of two divalent negative radicals and one monovalent positive radical.
Answer» ANSWER :FALSE

Discussion

1134.	A test tube filled with water is dipped up to its neck in a boiling water bath . Does the water inside the test tube boil? Justify.
Answer» Solution :The water in the test TUBE becomes hot but does not boil. The water in the tube gets the HEAT from the water outside. As the maximum TEMPERATURE of water in the container outsideis `100^(@)C`, the water inside the test tube attain `100^(@)C` temperature, but immediately the transmission of heat stops DUE to thermal equilibrium and hence the water inside the test tube cannot boil..

Discussion

1135.	A substance with fixed chemical composition.
Answer» SOLUTION :COMPOUND

Discussion

1136.	A student was asked to prepare oxygen from KClO_(3) in the laboratory. After th experiment was over, he put the burner off immediately. What do you think happened then?
Answer» Solution :(i) Collection of oxygen. (ii) Experimental set-up. (III) Changes that take PLACE after the burner is PUT off. (iv) EFFECT of these changes.

Discussion

1137.	A student of VIII class broke a dry cell to examine its parts ansd correlate them with his teacher's explanations about dry cells. In the chemistry class, the student asked his teacher that though graphite is a nonmetal, why is it used as electrods in the electrolytic process, especially where a high temperature is maintained. Write down the explanation the teacher gave to the student.
Answer» Solution :GRAPHITE is a good conductor of electricity and it is inert to most of the electrolytes. It has very high THERMAL resistivity . Due to these PROPERTIES, graphite is used in making electrodes in the process of ELECTROLYSIS.

Discussion

1138.	A student is carrying out distillation process in the lab. Water is boiling in the distillation flask. Water that is collected in the receiver flask is refrigerated and ice cubes are formed. Ice cubes are then kept outside the refrigerator and they started melating. Arrange the following phases of water in theascending order of their total (P.E + K.E) energy considering that the mass of water remains the same. (a) Water collected in the receiving flask. (b) Water boiling in the distillation flask. (c ) Steam passing through the delivery tube. (d) Ice cubes formed in the refrigerator.
Answer» dcba dabc cdba dacb Solution :d a B c (i) Ice cubes formed in the REFRIGERATION (ii) WATER collected in the receiving flask (iii) Water boiling in the distillation flask (iv) STEAM passing through the delivery tube

Discussion

1139.	Astable neutral atom of a element contains three fully filled orbits. Find the atomic number of the element.
Answer» SOLUTION :(i) Maximum number of electrons in each orbit. (ii) Number of electrons in valence shell of a stable ATOM. (III) Electronic configuration (IV) 36

Discussion

1140.	A solution that has maximum amount of solute dissolved in it.
Answer» ANSWER :SATURATED SOLUTION

Discussion

1141.	A solid nonmetal A on exposure to air forms a compound B which on dissolution in water forms the highest oxy acid C. Identify different type of salts which can be formed when C reacts with caustic potash
Answer» SOLUTION :`4P+5O_2rarr2P_2O_5` `A""B` `P_2O_5+2H_2Orarr2H_3PO_4` `A""B` `H_3PO_4+KOHrarrKH_2PO_4+H_2O` `H_3PO_4+KOHrarrK_2HPO_4+2H_2O` `H_3PO_4+3KOHrarrK_3PO_4+3H_2O`

Discussion

1142.	A solid nonmetal X on burning gives a compound Y which under high temperature and pressure conditions in presence of catalyst gets oxidised to Z. Z can give the ic acid of the nonmetal on dissolution in water. However, it is not a preferred reaction for the preparation ofthe acid. Give reason and explain the method employed for the preparation of the it: acid from Z and mention the precautions required during dilution of the acid.
Answer» Solution :`S+O_2rarr SO_(2)` `X""Y` `2SO_4+O_2("High pressure and temp ")/(V_2O_5)2SO_3` `Y""Z` `SO_3+H_2O rarr H_2 SO_4` However , in the PREPARATION of `H_2SO_4` the above reaction is not preferred since it is highly exothemic and leads to EXPLOSION .Instead, `SO_3` is DISSOLVED in `H_2SO_4` to give oleum which on dilution with give oleum which on dilution with water gives `H_2SO_4` `SO_3+H_2SO_4rarr H_2S_2O_7` Oleum `H_2S_2O_7+H_2Orarr2H_2SO_4` Dilution of `H_2SO_4` is shold not be diluted by adding water to the acid .Instead , water is taken and `H_2SO_4` is ADDED slowly by stirring dilution process.

Discussion

1143.	A soil is supplied with ammonium phosphate fertilizer. Which of the following types of bacteria is not involved in the process ofthc absorption of this fertilizer by plants
Answer» Anunonifying BACTERIA Nitrosifying bacteria Nitzifying bacteria NONE of these SOLUTION :CHOICE (1)

Discussion

1144.	A soil is highly deficienty in nitrigen . The crop requires nitrogen for immediate requirement as well as long term requirement . Which among the following is the most suitble fertilizer for the soil ?
Answer» Urea Ammonium SULPHATE Ammonium nitrate CALCIUM ammonium nitrate SOLUTION :CHOICE (4)

Discussion

1145.	A small crystal of solute is added to unsaturated, saturated and supersaturated solutions, what observations do you find ? Justify
Answer» SOLUTION :(i) Changes that TAKES place in particle size of solute in respective solutions. (ii) Comparision of amount of solutes present in respective solutions. (iii) RELATION between changes with respect to CRYSTAL of solute and nature of the solution.

Discussion

1146.	A series of chemical reactions were carried out in a laboratory in the following way. At first zinc granules reacted withH_2SO_4 to form H_2 gas. Then hydrogen gas reacted with chlorine gas under diffused sunlight to form hydrogen chloride gas. Hydrogen chloride gas produced in this process was dissolved in water to form hydrochloric acid. Hydrochloric acid reacted with sodium hydroxide to form soruum chloride and water. Sodium chloride thus produced is first melted and then electricity is passed through it. Due to the passage of electricity through sodium chloride, sodium n1etal and chlorine gas is obtained. Rahul was asked to arr:mge the above reactions in the order of combination, decomposition, displacement and double decomposition. His answer is given below. (a) Formation of H_2 gas. (b) Formation of hydrogen chloride gas. (c) Formation of sodium and chlorine from sodium chloride. (d) Fomation of sodium chloride. Which among the following orders given below is correct, according to you?
Answer» c d b a b c a d a b c d b c d a Solution :`Zn+H_2SO_4toZnSO_4+H_2`, DISPLACEMENT reaction `H_2+Cl_2to2HCl`, combination reation `2NaClto2Na+Cl_2` decomposition reaction Hence the ORDER is b, c, a, d (i) Formation of hydrogen CHLORIDE gas. (ii)Formation of sodium and CHLORINE from sodium chloride. (iii)Formation of `H_2`gas. (iv)Formation of sodium chloride.

Discussion

1147.	A saturated solution has:
Answer» LESS solute more solvent maximum solute no solute Answer :C

Discussion

1148.	A sample of common salt obtaied from sea water contain 39 g of NaCl and 1 g KCl. If it is dissolved in 100 g of water and then 90 g water is evaporated, what observation do you find at 0^(@)C? What is the maximum amount of pure NaCl that can be obtained by the above method ? (Solubilities of NaCl and KCl aer 40 g, 55 g to 100^(@)C and 35 g 28 g at 0^(@)C respectivety)
Answer» Solution :At `100^(@)C,` the solubilites NaCl and KCl are 40 and 55 respectively. Therefore entire sample dissolves in 100 g of wae. When 90 g of water is evaporated, 10 g of wate remains and since the solution to cooled to `0^(@)C` it can contain 3.5 g NACl and 2.8 g KCl.That means the entire KCl (1 gram) remains in solution which remains unsaturated wrt KCl.In 10G of watrer only 3.5 g remains in DISSOLVED state thereby making the solution saturated wrt NaCl. The rest of the NaCl that is 35.5 g gets precipitated out. This is the maximum amount of NaCl that can to obtained in pure FORM.

Discussion

1149.	A polymer is made of many ______ units.
Answer» ANSWER :C

Discussion

1150.	A piece of red litmus paper is dipped into the water kept in beaker A and B. (a) In beaker 'A' some amount of CaO was poured. (b) SO_(2) gas was passed through beaker 'B' Write the observation made in both the cases.
Answer» SOLUTION :(i) Product FORMED in A (ii) COLOUR CHANGE on litmus in A (iii) Products formed in B (IV) Colour change on litmus in B.

Discussion

Explore topic-wise InterviewSolutions in .

An atom of an element has one electron in the valence shell and the two consecutive inner shells have 8 electrons each. Find the atomic number of that element. Write the electronic configruation of preceding nad succeding elements.

An atom of an element has mass number 31. It has 16 neutrons. The valence shell and the number of valence electrons, respectively, could be

An atom of an element has 4th shell as the valence shell. The difference between electrons present in L and M and N shells are 1 and 0 respectively. Find the atomic number of an element.

An atom is considered to be electrically

Amphoteric oxides are ……………….. Oxides that show both acidic and basic properties.

Among white phosphorous and red phosphorous which is more preferable for use in match sticks? Give reason in support of your answer

Among the following oxides which one is converted to metal by treated with hydrogen ?

Among all the layers of atmosphere the layer with the highest temperature is________.

Ammonium chloride can be separated from salt by .................. (evaporation/ sublimation)

Aluminium reacts strongly with cold water to form hydroxide.

Aluminium oxide is following type of an oxide.

Aluminiumfoil can be made from aluminium by using

Alloys are homogeneous mixtures.

......................allotropes of carbon do not have a definite geometric shape.

Allotropes have the same.....................properties and different.....................

All matter is made up of tiny particles called ______ or ______

All atoms of an element are identical.

Air is a mixture.

Ag+CuSO_4toCu+AgSO_4 Is this reaction possible ? Explain.

Addition of potassium nitrate to ice results in

According to Thomson

According to the kinetic molecular theory, explain the following. (a) Density of a solid is the highest. (b) Gases are highly compressible whereas solids are incompressible. (c ) Liquids and gases are fluids whereas solids are rigid.

According to Rutherford electrons revolve around the nucleus in ______.

According to Rutherford ______ force of nucleus is balanced by the high velcoity of revolving electrons.

According to Rutherford , electrons move around thenucleus in circular paths. How did the correlate this with the stability of an atom.

According to law of conservation of mass:

According to Bohr's theory , the electrons revolve round the nucleus in definite paths called orbits . Do the electrons revolve round with same speed in all orbits? Justify.

According to Bohr's atomic model, electrons revolve in ______ orbits.

Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?

A_2X is comprised of two divalent negative radicals and one monovalent positive radical.

A test tube filled with water is dipped up to its neck in a boiling water bath . Does the water inside the test tube boil? Justify.

A substance with fixed chemical composition.

A student was asked to prepare oxygen from KClO_(3) in the laboratory. After th experiment was over, he put the burner off immediately. What do you think happened then?

Astable neutral atom of a element contains three fully filled orbits. Find the atomic number of the element.

A solution that has maximum amount of solute dissolved in it.

A solid nonmetal A on exposure to air forms a compound B which on dissolution in water forms the highest oxy acid C. Identify different type of salts which can be formed when C reacts with caustic potash

A soil is supplied with ammonium phosphate fertilizer. Which of the following types of bacteria is not involved in the process ofthc absorption of this fertilizer by plants

A soil is highly deficienty in nitrigen . The crop requires nitrogen for immediate requirement as well as long term requirement . Which among the following is the most suitble fertilizer for the soil ?

A small crystal of solute is added to unsaturated, saturated and supersaturated solutions, what observations do you find ? Justify

A saturated solution has:

A polymer is made of many ______ units.

A piece of red litmus paper is dipped into the water kept in beaker A and B. (a) In beaker 'A' some amount of CaO was poured. (b) SO_(2) gas was passed through beaker 'B' Write the observation made in both the cases.

All matter is made up of tiny particles called or