1214 + Interview Questions in Chemistry in Class 8 Page 22 InterviewSolution

1051.	Can molten copper be used in place of molten iron for the manufacture of artificial diamonds ? Give reason in support of your answer.
Answer» Solution :(i) Condition required for the manufacture of diamond. (II) Comparison of change in VOLUME of FIXED MASS of iron and copper during solidification. (III) Effect of this change on the rearrangment of atoms of carbon. (iv) Relation between the arrangement of atoms and the allotropic form.

Discussion

1052.	Calculate the number of neutrons for the following elements. (a) ""_(11)Na^(23)""(b)""_(18)Ar^(40)""(c)""_(17)Cl^(36)""(d)""_(15)P^(31)
Answer» SOLUTION :NUMBER of NEUTRONS =A-Z

Discussion

1053.	Calcium reacts vigorously even with cold water.
Answer» ANSWER :t

Discussion

1054.	CaCO_(3) + ………to CaCl_(2) + H_(2)O + ……………
Answer» ANSWER :DIL. 2HCL ; `CO_(2)`

Discussion

1055.	Burning more and more fossil fuels creates an imbalance in the netural cabon cycle as well as in the natural water cycle. Give reasons.
Answer» SOLUTION :(i) Products of COMBUSTION of fuels. (ii) Effect of products formed on environment. (iii) REACTIVITY of products with rain WATER. (iv) Effect on carbon and water cycle.

Discussion

1056.	Brass is not suitable for type making because
Answer» brass expands on solidification. brass CONTRACTS on solidification. brass has less tensile STRENGTH. brass has less DUCTILITY. Answer :B::C

Discussion

1057.	Both slow cooling and rapid cooling of glass are avoided. How do you account for this?
Answer» SOLUTION :(1) Thermal conductivity of glass. (ii) Importance ofprocess of cooling of SOFTENED glass to OBTAIN good quality of glass. (iii) CHANGES that takes place in the quality of glass on rapid cooling (iv) Changes that takes place in the quality of glass on slow cooling. (v) Relation between the process of cooling of glass and its physical properties.

Discussion

1058.	Both H_2SO_4 and HNO_3 cause damage to skin when the skin comes in contact with them. Compare and contrast the reasons
Answer» Solution :`H_2SO_4` being a dehydrating agent removeshydrogen and oxygen from the skin in the FORM of water there by amaging the skin. `HNO_3` REACTS ITH skin proteins forming xanthoproteins and hence imparts YELLOW colour to skin and forms painful blisters

Discussion

1059.	Bone charcoal contains maximum percentage of ________.
Answer» SOLUTION :CALCIUM PHOSPHATE

Discussion

1060.	Bone ash contains both micro and macro nutrients in it. However it is not used as a fertilizer. It is converted to superphosphate oflime which is an important fertilizer. Give reason
Answer» Solution :(i) REQUISITE of a good fertilizer. (ii) Constituent of bone ash which CONTAINS macro--nutrients required for plants. (iii) Soluble NATURE of the above constituent. (iv) Manufacture of super phosphate oflime from this constituent. (v) SOLUBILITY of'super phosphate of lime.

Discussion

1061.	Boiling occurs throughout the liquid.
Answer» ANSWER :1

Discussion

1062.	Blue coloured CuSO_(4) solution is taken in a beaker. Is the blue solution an elementcompound or mixture? Is it homogeneous or heterogeneous?
Answer» SOLUTION :COMPONENTS PRESENT in the solution.

Discussion

1063.	Blue coloured CuSO_4 is taken in two test tubes A and B. Zinc granules are added to test tube A and small iron piecces are added to test tube B. Explain the observations in each acse by giving reasons.
Answer» SOLUTION :(i) Reactivity series of metals. (II) Reactivity of metals according to metal reactivity series. (iii)Reactions TAKING place. (iv)CHANGE in property of the solution DUE to the reaction.

Discussion

1064.	Blue coloured gas X having a characteristic fishy odour, can restore the colour of lead parntmgs. Thi.s gas X can also be used for sterilizing water. identify the gas X. Mention the type of reaction(s) involved.
Answer» Solution :Since X is a GAS which is USED in STERILIZING water and has a characteristic FISHY odour, it is `O_3.O_3` combines with black LEAD sulphide to give sulphate. It is a redox reaction. `PbS+4O_3toPbSO_4+4O_2`

Discussion

1065.	Bleaching powder in cold water is an excellent bleaching agent. But it cannot act as a good bleaching agent when dissolved in hot water.Why?
Answer» Solution :BLEACHING powder reacts with cold water to produce chloride and hypochlorite ions. Hypochlorite ions dissociate producing NASCENT oxygen Which is RESPONSIBLE for bleaching `CaOCL_2+H_2O rarrCa^(+2)+CL^(-)+ClO+H^++OH^-` Bleaching powder reacts with hot water and produces chloride and chlorate ions `3ClO^(-)rarr2Cl^(-)+ClO^-`

Discussion

1066.	Basic unit of a diamond crystal has a.....................shape.
Answer» ANSWER :TETRAHEDRAL

Discussion

1067.	How can we make a chemical equation more informative?
Answer» SOLUTION :BALANCED equation `2Mg(s)+O_(2)(G)overset("heat")rarr2MgO(s)`

Discussion

1068.	Avoid plastics as far as possible'. Comment in this advice.
Answer» Answer :Plastics are non-biodegradable materials, i.e. they cannot be easily DECOMPOSED by NATURAL PROCESSES and take several years to DECOMPOSE.

Discussion

1069.	Atoms of two element P and Q have 5 electrons in 2nd shell and 3rd shell respectively . What could be the geometrical representations of P and Q ? What will the atomic numbers of these elements be ?
Answer» <P> Solution :(i) Number of VALENCE electrons of P and Q and their electronic configuration. (ii) Calculation of number of electrons in PREVIOUS shells of P and Q based on the valence shell and the number of electrons in the valence shell.

Discussion

1070.	Atomic number is the sum of number of protons and neutrons.
Answer» ANSWER :F

Discussion

1071.	Atomic mass of reactants should be equal to the ……………… of products.
Answer» SOLUTION :ATOMIC MASS

Discussion

1072.	Assertion (A): Electrons present in ground states of different single electron species (H,He^(+), Li^(++)) possess different amount of energy. Reason (R) : Distances of electrons from the nuclei of different single electron are equal.
Answer» Both A and R are correct and R is the correct explanation of A. Both A and R are correct and R is not the correct explanation of A. A is correct and R is wrong A is wrong and R is correct Solution :The electrons present in different single electon species posses different amounts of ENERGY due to the difference in the atomic numbers. The DISTANCE of the electrons from the NUCLEI of different single ELECTRON species is different because of difference in atomic number.

Discussion

1073.	Electrons are distributed in different energy shells, according to the rules of
Answer» SOLUTION :ELECTRONIC CONFIGURATION

Discussion

1074.	Arrange the steps in the process of carbon cycle, starting from the abundant state of existence of carbon in the combined state, in their correct sequence. (a) Dead remains(b) CO_(2) in atmosphere (c ) Organic matter (d) Plants. (e ) Fossil fuels
Answer» bacde bdace dbcae debaca Solution :(i) `CO_(2)` in atmosphere (ii) PLANTS (iii) Dead remainsltbvrgt (iv) ORGANIC MATTER (V) Fossil fuels

Discussion

1075.	Arrange the step in the process of carbon cycle, starting from the substance which possess a mixture of hydrocarbons, in a proper sequence. (a) Sea water (b) Dead remain ( c) Aquatic plants (d) CO_(2) in atmosphere ( e) Organic matter (f) Fossil fuels.
Answer» cadefb fcdabe dacbef fdacbe Solution :(i) Fossil FUELS (ii) `CO_(2)` in ATMOSPHERE (iii) Sea water (iv) AQUATIC plants (v) Dead remains (vi) ORGANIC matter

Discussion

1076.	Arrange the products of the following reactions in the increasing order of the numbre of oxygen atoms associated with one nonmetallic atom. (a) Burning of phosphorus in an adequate supply of oxygen to produce and oxide of phosphorus. (b) The complete combustion of coke with the supply of sufficient oxygen. (c) An electric spark is provided to a 1 : 1 mixture of nitrogen and oxygen. (d) Burning of sulphur dioxide gas in oxygen.
Answer» c d a b c b a d b c a d c b d a Solution :(a) BURNING of phosphorus gives `P_(2)O_(5)` (b) Complete combustion gives `CO_(2)` (c) When an electric spark is PROVIDED to a mixture 1 : 1 mixture of `N2andO_(2),NO` is produced. (d) Burning of `SO_(2)` gives `SO_(3)` `:.` The correct sequence is c b a d. Arrange the the STATEMENTS in this order - (i), (II), (iii), (iv).

Discussion

1077.	Arrange the given combustible substance in decreasing order of calorific value. (a) Hydrogen (b) Charcoal (c ) Petrol (d) L.P.G( e) Wood
Answer» bcade adcbe badec baced Solution :(i) HYDROGEN (ii) L.P.G (iii) Petrol (IV) CHARCOAL (v) WOOD

Discussion

1078.	Arrange the following steps involved in the prepartion of oxygen from KClO_(3) in proper order. (a) Content of the test tube is heated. (b) A mixture of finely ground KClO_(3)andMnO_(2) is taken in a test tube. (c) The open end of the test tube is plugged with cotton. (d) Delivery tube is taken out. (e) The test tube is fixed in a slanting position. (f) Bunsen burner is put off. (g) Oxygen is collected by downward displacement of water.
Answer» b c d a e f g e f c b d a g a b c d f g e b c e a g d f Solution :(i) A MIXTURE of finely ground `KClO_(3)andMnO_(2)` is taken in a test tube. (ii) The open end of test tube is PLUGGED with cotton. (iii) The test tube is fixed in a SLANTING position. (iv) Content of the test tube is heated. (v) Oxygen is collected by downward displacement of water. (vi) Delivery tube is taken out. (vii) BUNSEN burner is PUT off.

Discussion

1079.	Arrange the following statements in a sequence which involves the calculation of the atomic number and mass number for an atom of an element with 15 electrons and 16 neutrons. (a) A=Number of protons + Number of neutrons A=Z+ Number fo neutrons A=15+16=31(b) Number of protrons and number of electrons are equal in a neutral atom. Hence the atomic number Z is equal to 15. (c) Mass number is equal to the total number of protons and neutrons. (d) Atomic number is 15 and mass number is 31.
Answer» b d c a b c a d c b a d c b d a Solution :(i) NUMBER of protons and number of electrons are equal in a NEUTRAL atom. Hnce atomic number 'Z' is equal to 15. (ii) Mass number is equal to the TOTAL number of protons and neutrons. (iii) A = Number of protons + Number of neutrons A = Z + Number of neutrons A = 15 + 16 = 31 (IV) Atomic number is 15 and mass number is 31.

Discussion

1080.	Arrange the fol.lowing reactions in the given order that is compound-element combination, compound- compound combination, clement-clement combination. (a) Coke is burnt in an inadequate supply of air. (b) The product formed in the reaction (a) is again bun1t in the presence of oxygen. (c) The product fonned in the reaction (b) is treated with water.
Answer» a c b b c a b a c c a b Solution :`2C("coke")+O_("inadequate")to2CO` is ELEMENT combination `2CO+O_2to2CO_2` is compound - element combination `CO_2+H_2OtoH_2CO_3` is compound - compound combination (i)The product FORMED in reaction (a) is again burnt in the presence of oxygen. (ii) The product formed in reaction (b) is treated with WATER. (iii) Coke is burnt in an inadequate supply of AIR

Discussion

1081.	Arrange the following products (oxides) in the ascending order of the ratio of metal atoms to oxygen atom(s) present in one molecule of the respective oxide. (a) Magnesium is heated in the presnce of oxygen. (b) Iron produces a reddish brown with a crackling sound when it is heated higher temperautre. (c) Sodium undergoes oxidation in moist air. (d) Formation of a coating of aluminium oxide on aluminium at normal temperature.
Answer» a d C b d b a c a c b d c a b d Solution :(i) Formation of coating of aluminium oxide `(Al_(2)O_(3))` on aluminium at normal temperature. Here the ratio ofmetal atom(s) to oxide is 2/3 that is.0.67 (ii) Iron gives a reddish brown POWDER with crackling sound when it is heated at a higher temperature. Here the ratio of metal ATOMS to oxygen atoms in one molecule of oxide is `3//4` that is 0.75 (iii) Magnesium oxide (MgO) is formed when magnesium is slightly heated with oxygen. Here the ratio of metal atom to oxygen atom is 1. (iv) SODIUM oxide `(Na_(2)O)` is formed when sodium undergoes oxidation in moist air. Here the reaction of metal atoms to oxygen atom is 2.

Discussion

1082.	Arrange the following radicals in the increasing order of total number of constituent atoms present in the respective radicals. (a) Hydroxide(b) Nitride(c) Chromate (d) Sulphite(e) Dihydrogen phosphate
Answer» SOLUTION :

Discussion

1083.	Arrange the different type of coal in sequence in the increasing order of the quality coal. (a) Lignite (b) Peat (c) Anthracite (d) Bituminous
Answer» acdb dbca badc bcda Solution :(i) PEAT (ii) Lignite (III) Bituminous (iv) ANTHRACITE

Discussion

1084.	Arrange the different forms ofsulphur formed during heating fouowed by cooling Meu sulphur Flower of sulphur Rhombic sulphur sulphur vapoar Lambda sulphur Monoclinic sulphur
Answer» e c f a d b c f e a d b c f ae d b c f e a b d Solution :(i) Rhombic sulphur (ii) Monochnic sulphur (iii) LAMBDA sulphur (IV) Meu sulphur (v) Sulphur vapour (VI) Flower of sulphur

Discussion

1085.	Arrange the chemicals in sequence for the removal of impurities H_(2)S,SO_(2), PH_(3) and H_(2)O respectively in the purification of hydration gas. (a) Phosphorus pentoxide(b) Lead nitrate solution (c) Silver nitrate solution(d) Caustic potash
Answer» a B c d b c a d b d c a a d b c SOLUTION :(i) Lead nitrate solution (II) Cautic POTASH (iii) Silver nitrate solution (iv) Phosphorus pentoxide

Discussion

1086.	Aqueous solutions are good conductors in comparison to its corresponding pure solvent.
Answer» ANSWER :TRUE

Discussion

1087.	Anode rays produced by isotopes and isobars possess same charge when taken in different discharge tubes. Which among the two sets of anode rays show different deflections in the presence of electric field ?
Answer» Solution :(i) Characteristics of ISOTOPES and isobars. (II) FACTORS AFFECTING e/m of anode rays. (iii) Relation between e/m and deflection.

Discussion

1088.	"Anode rays are also produced along with cathode rays in the discharge tube pressure ". Justify.
Answer» Solution :(i) Density of gas MOLECULES inside the discharge tube. (ii) The mechanism of PRODUCTION of cathode RAYS. (iii) The ORIGIN of anode rays.

Discussion

1089.	Anhydrous substance is the one that does not contain ..................
Answer» ANSWER :WATER of CRYSTALLIZATION

Discussion

1090.	Anhydride of sulphurous acid is
Answer» SULPHUR dioxide sulphate ion sulphur trioxide Sulphite ion Answer :A::C

Discussion

1091.	Anhydride of an acid X contains 2 phosphorous atoms, 5 oxygen atoms. If this acid X is made to react with bases like sodium hydroxide, calciurn hydroxide and aluminum hydroxide, what will the formulae of the corresponding normal salts formed be?
Answer» Solution :(i) Identification of X from the respective anhydride. (ii) PREDICTING the formulae of the bases based on nomenclature. (iii) Nature of reaction between ACID X and respective bases. (iv) Predicting the VALENCY of negative redical in X. (V) Predicting the valency of sodium, calcium and aluminium RESPECTIVELY. (vi)Applying crisscrossmethod to determine formulae of the corresponding salts.

Discussion

1092.	..................and...............are some of the main sources of water on earth.
Answer» ANSWER :Sea, RIVER, LAKE, WELL, RAIN

Discussion

1093.	........and ...........affect the solubility of a solute in water.
Answer» ANSWER :Stirring/temperature and SIZE of SOLUTE PARTICLES

Discussion

1094.	An oxide X of carbon on treatment with oxygen gives Y which turns line water miky and blue litmus to red. Predict the valencies of carbon in X and Y and what is the composition of miky precipitate formed?
Answer» SOLUTION :(i) Identification of Y from the GIVEN data. (ii) Identification of X from Y (iii) Predicting the VALENCIES of carbon in X and Y (IV) Reaction between Y and lime WATER. (v) Composition of the above product.

Discussion

1095.	An oxide of a bivalent metal on heating with coke gives a compound 'X' and a gas 'Y'. The gas 'Y' reacts with chlorine gas to give a poisonous gaseous compound. 'X' undergoes hydrolysis to give a hydrocarbons 'Z' with two carbon atoms. Identify the compound X,Y, and Z. Also give the reactions involved.
Answer» Solution :(i) Identification of HYDROCARBONS. (ii) Identification of metal which GIVES hydrocarbons with 2 carbon atoms on hydrolysis. (iii) Products formed on reaction of metal oxide with coke. (iv) Reaction of gaseous product with CHLORINE.

Discussion

1096.	An increase in the levels of CO_(2) in the atmosphere increases the temperature of the earht.
Answer» ANSWER :1

Discussion

1097.	An eleven-year old naughty boy Krish took keys of his father's car without his father's permission. He went inside the garage, colsed it and started the ignition. After a few minutes, he started couging. His father fortunately went into the garage, opened it , immediately brought him out and rescued him. Krish's mother asked her husband- the reason for Krish's condition. What explanation did the father give ?
Answer» Solution :The burning of fuel takes place while starting a car. If fuel is burnt in a closed system, INCOMPLETE combustion takes place resulting in the FORMATION of CO due to inadequate supply of AIR. CO is very HARMFUL for health because of the formation of carboxyhaemoglobin.

Discussion

1098.	An atoms 'X' is made up of 20 protons and 20 neutrons. Write the atomic number and mass number and represent the atom with atomic number and number.
Answer» Solution :(i) ATOMIC number equal to PROTON number (II) Mass number equal to sum of proton and neutrons number

Discussion

1099.	An atom of an element has two electrons in the valence shell and two consecutive inner shells have 8 electrons each. Calculate the atomic number of the element.
Answer» 19 20 30 18 Solution :Electronic CONFIGURATION of atom of ELEMENT which has two electrons in the valence shell and two consecutive inner SHELLS have 8 electrons each is 2,8,8,2. And hence atomic number is element=20

Discussion

1100.	An atom of an element has one electron in the valence shell and the two inner shells have 8 electrons each. Find the atomic number of that element.
Answer» Solution :(i) NUMBER of ELECTRONS PRESENT in K,L and M shells of that atom. (ii) Determination of (n-1) and (n-2) BASED on the number of electrons in the previousshell. (iii) Electronic configuration (iv)ATOMIC number.

Discussion

Explore topic-wise InterviewSolutions in .

Can molten copper be used in place of molten iron for the manufacture of artificial diamonds ? Give reason in support of your answer.

Calculate the number of neutrons for the following elements. (a) ""_(11)Na^(23)""(b)""_(18)Ar^(40)""(c)""_(17)Cl^(36)""(d)""_(15)P^(31)

Calcium reacts vigorously even with cold water.

CaCO_(3) + ………to CaCl_(2) + H_(2)O + ……………

Burning more and more fossil fuels creates an imbalance in the netural cabon cycle as well as in the natural water cycle. Give reasons.

Brass is not suitable for type making because

Both slow cooling and rapid cooling of glass are avoided. How do you account for this?

Both H_2SO_4 and HNO_3 cause damage to skin when the skin comes in contact with them. Compare and contrast the reasons

Bone charcoal contains maximum percentage of ________.

Bone ash contains both micro and macro nutrients in it. However it is not used as a fertilizer. It is converted to superphosphate oflime which is an important fertilizer. Give reason

Boiling occurs throughout the liquid.

Blue coloured CuSO_(4) solution is taken in a beaker. Is the blue solution an elementcompound or mixture? Is it homogeneous or heterogeneous?

Blue coloured CuSO_4 is taken in two test tubes A and B. Zinc granules are added to test tube A and small iron piecces are added to test tube B. Explain the observations in each acse by giving reasons.

Blue coloured gas X having a characteristic fishy odour, can restore the colour of lead parntmgs. Thi.s gas X can also be used for sterilizing water. identify the gas X. Mention the type of reaction(s) involved.

Bleaching powder in cold water is an excellent bleaching agent. But it cannot act as a good bleaching agent when dissolved in hot water.Why?

Basic unit of a diamond crystal has a.....................shape.

How can we make a chemical equation more informative?

Avoid plastics as far as possible'. Comment in this advice.

Atoms of two element P and Q have 5 electrons in 2nd shell and 3rd shell respectively . What could be the geometrical representations of P and Q ? What will the atomic numbers of these elements be ?

Atomic number is the sum of number of protons and neutrons.

Atomic mass of reactants should be equal to the ……………… of products.

Assertion (A): Electrons present in ground states of different single electron species (H,He^(+), Li^(++)) possess different amount of energy. Reason (R) : Distances of electrons from the nuclei of different single electron are equal.

Electrons are distributed in different energy shells, according to the rules of

Arrange the steps in the process of carbon cycle, starting from the abundant state of existence of carbon in the combined state, in their correct sequence. (a) Dead remains(b) CO_(2) in atmosphere (c ) Organic matter (d) Plants. (e ) Fossil fuels

Arrange the step in the process of carbon cycle, starting from the substance which possess a mixture of hydrocarbons, in a proper sequence. (a) Sea water (b) Dead remain ( c) Aquatic plants (d) CO_(2) in atmosphere ( e) Organic matter (f) Fossil fuels.

Arrange the given combustible substance in decreasing order of calorific value. (a) Hydrogen (b) Charcoal (c ) Petrol (d) L.P.G( e) Wood

Arrange the following radicals in the increasing order of total number of constituent atoms present in the respective radicals. (a) Hydroxide(b) Nitride(c) Chromate (d) Sulphite(e) Dihydrogen phosphate

Arrange the different type of coal in sequence in the increasing order of the quality coal. (a) Lignite (b) Peat (c) Anthracite (d) Bituminous

Arrange the different forms ofsulphur formed during heating fouowed by cooling Meu sulphur Flower of sulphur Rhombic sulphur sulphur vapoar Lambda sulphur Monoclinic sulphur

Arrange the chemicals in sequence for the removal of impurities H_(2)S,SO_(2), PH_(3) and H_(2)O respectively in the purification of hydration gas. (a) Phosphorus pentoxide(b) Lead nitrate solution (c) Silver nitrate solution(d) Caustic potash

Aqueous solutions are good conductors in comparison to its corresponding pure solvent.

Anode rays produced by isotopes and isobars possess same charge when taken in different discharge tubes. Which among the two sets of anode rays show different deflections in the presence of electric field ?

"Anode rays are also produced along with cathode rays in the discharge tube pressure ". Justify.

Anhydrous substance is the one that does not contain ..................

Anhydride of sulphurous acid is

Anhydride of an acid X contains 2 phosphorous atoms, 5 oxygen atoms. If this acid X is made to react with bases like sodium hydroxide, calciurn hydroxide and aluminum hydroxide, what will the formulae of the corresponding normal salts formed be?

..................and...............are some of the main sources of water on earth.

........and ...........affect the solubility of a solute in water.

An oxide X of carbon on treatment with oxygen gives Y which turns line water miky and blue litmus to red. Predict the valencies of carbon in X and Y and what is the composition of miky precipitate formed?

An increase in the levels of CO_(2) in the atmosphere increases the temperature of the earht.

An atoms 'X' is made up of 20 protons and 20 neutrons. Write the atomic number and mass number and represent the atom with atomic number and number.

An atom of an element has two electrons in the valence shell and two consecutive inner shells have 8 electrons each. Calculate the atomic number of the element.

An atom of an element has one electron in the valence shell and the two inner shells have 8 electrons each. Find the atomic number of that element.