1214 + Interview Questions in Chemistry in Class 8 Page 24 InterviewSolution

1151.	A nonmetal X forms two oxides, A and B. The ratio of weight of the element X to the weight of oxygen in A and B is 7 : 20 and 7 : 16 respectively. If the molecular mass of the oxide, A is 1 08, identify A and B.
Answer» Solution :In 108 G of `A,7/27xx108=28g` of A is present. Since the velency of oxygen is 2, we can consider the formula of A is `X_2O_2` `:. A=(108-28)/16=5" and the formula of "` A is `X_2O_5`, Atomic weight of X 28/2 = 14 `:. "ELEMENT X is NITROGEN, and A is "N_2O_5`. Let the formula of B is `N_2O_b` Since the ratio of N and O in B is 7 : 16, the number of oxygen atoms present in B is 4[`:.28g`of nitrogen combines with 64 g of oxygen] `:. " formula of B is "N_2O_4 (or)NO_2`

Discussion

1152.	A neutral atom of an element has a nucleus with nuclear charge 12 times and mass 24 times that ofhydrogen. Calculate the number of electrons, protons and neutronsin its stable positively charged ion.
Answer» Solution :(i) Number of electrons required to be PRESENT in the valence SHELL of an ionso that the ion beomes STABLE. (ii) Subatomic particles that CAUSE nuclear charge. (iii) Number of subatomic particles (iv) Electronic CONFIGURATION of the stable ion that is formed.

Discussion

1153.	A naturally occurring minerals of sedimentary rocks on heating to high temperatures decomposes giving a solid 'A' and a gas. The solid on dissolution in water undergoes chemical reactions which is associtated with hissing sound and the solution appears to be boiling. Compound 'B' formed during this reaction on long standing forms a layer of white powder. When excess CO_(2) is passed through this milky white solution, a clear solution is formed again. Identify the substances and justify the above observations. Give reasons wherever required.
Answer» Solution :Limestone is the naturally OCCURRING mineral in sedimentary ROCKS. This contains calcium carbonate which on decomposition at high TEMPERATURE gives solid CaO and `CO_(2)`. CaO on reaction with water forms `Ca(OH)_(2)`. This is highly exothermic reaction and `CO_(2)` gas is evolved during this reaction. THEREFORE, the solution appears to be BOILING and is associated with hissing sound. On long exposure to air, this reacts with atmospheric `CO_(2)` to form `CaCO_(3)` as a white powdered layer. On passing excess `CO_(2),CaCO_(3)` reacts with this forming soluble calcium bicarbonate. Therefore, a clear solution is formed again.

Discussion

1154.	A mixture of 95% oxygen and 5% CO_(2) is called _____.
Answer» SOLUTION :CARBOGEN

Discussion

1155.	A mixture is formed by two kinds of matter, the molecules of which possess only vibratory motion. If the change in solubililty of two substancesin a given solvent differs widely with the change in temperature, how can these twosolids be separted from the solvent?
Answer» Solution :Solids possess the molecules which have only vibratory motion. Thus both the substances are solids. As their SOLUBILITY in a particular solvent DIFFERS in a particular RANGE of temperature, they can be separated by FRACTIONAL crystallisation

Discussion

1156.	A mixture consists of various components that are present in a fixed proportion.
Answer» ANSWER :F

Discussion

1157.	A metallic element forms an ion with unit charge. The ion has 10 electrons and 12 neutrons . What is the number of electrons, protons and neutrons in its neutral atom ? Represent the atom with atomic number and mass number.
Answer» Solution :(i) Metals from cations. (ii) The number of electrons in neutral atom BASED on the type of ion metals FORMED. (III) The atomic number of the metal. (iv) The calculation of mass number from atomic number and number of neutrons.

Discussion

1158.	A metal which is more reactive than calcium.
Answer» SOLUTION :Sodium/potassium

Discussion

1159.	A hydrocarbon on complete combustion produces176 g of carbon dioxide and 90 g of water. What will x the formula of hydrocarbon be and also give balanced chemical equation of combustion of hydrocarbon?
Answer» Solution :(i) General balanced chemical equation for COMBUSTION of hydrocarbon. (II)Calculationof the COEFFICIENTS of carbon dioxide and water USING the formula (III) Coefficient of `CO_2=("Amount of "H_2O" produced")/("Molecular weight ")` (iv)Coefficient of `H_2O=("Amount of "H_2O" produced")/("Molecular weight ")` (v) Chemical formula of hydrocarbon from the coefficients of corbon dioxide and water

Discussion

1160.	A gas which is combustible and can support combustion is.
Answer» oxygen. nitrous oxide. nitric oxide. carbon monoxide. Answer :B::C

Discussion

1161.	A di-positive ion has an electronic arrangement 2,8,8 . Find out the number of electrons, protons and neutrons in that element if its mass number is 40.
Answer» SOLUTION :(i) Calculation of the atomic NUMBER of the element. (ii) Calculation of the number of electrons in a neutral atom based on the configuration of positive ION. (III) The atomic number of a neutral atom (iv) The number of NEUTRONS in a neutral atom based on mass number. (v) 20,20,20

Discussion

1162.	A deliquescent substance does not become sticky in an air tight container . Justify.
Answer» Solution :The WATER VAPOUR present inside the airtight container is limited. After absorbing the water vapour, the deliquescent substance again RELEASE the water molecules to maintain . Hence is cannot become sticky in the AIR tight container.

Discussion

1163.	(a) Decomposition reactions are always initiated with the supply of energy. Give appropriate reasons. (b) Generally burning or combustion reactions are exothermic Justify.
Answer» Solution :(a) Since the atoms are bonded within the molecule by CERTAIN forces of attaction, energy is required to dissociate the molecules. Indecomposition reaction, breaking of BOND takes place. To break bonds energy is required. Hence the energy needs to be supplied to initiate most of the DECOMPOSITION reactions. (b)Burning of combustion is a combination of a substance with oxygen. As formation of bonds involves RELEASE of energy, combustions are GENERALLY exothermic.

Discussion

1164.	A compound 'X ' of silver on treatment with barium chloride gives the respective products Y and Z . X on treatment with sodium hydroxide gives A and B where A can also be obtained when silver is attacked by ozone and Bis the salt of an oxy acid of nitrogen which ends with the suffix '-ate'. Identify and give the chemical formulae of the substances X ,Y, Z, A and B?
Answer» Solution :(i) Identification of A from the PRODUCT formed by the REACTION of silver with OZONE. (II) Identification of X from B. (iii) Ifentification of Y and Z from X.

Discussion

1165.	A compound 'X' made of two non-metals, in a reaction with another non-metal 'Y' gives the hardest substance and carbon monoxide. Identify the compound X and non-metal Y.
Answer» `CO_(2),Si` `SiO_(2),C` `SiC,O_(2)` `CO,Si` ANSWER :B

Discussion

1166.	A cloudy heterogeneous solution in which the solute particles are visible with the eyes is called.............
Answer» ANSWER :SUSPENSION

Discussion

1167.	A china dish weighs 25 g when empty.When saturated solution of potassium chloride is poured into it at 40^(@)C , the weight of the dish is 63 g . When the solution is evaporated to dryness, the china dish along with crystals weighs 40 g. Find the solubility of potassium chloride at 40^(@)C .
Answer» Solution :Weight of SATURATED solution of KCl =63-25 =38g , Weight of crystal of KCl=40-25=15 g Weight of WATER contained in saturated solution =38-15=23 g `=("Weight of KCl crystals")/("Weight of water")xx100` `=(15)/(23)xx100=65.2` at `40^(@)C`

Discussion

1168.	A chemical reaction may show the following characteristics.
Answer» RELEASE of gas release of heat change in state all of the above Answer :D

Discussion

1169.	A chemical reaction involves ……………. And ……………. Of bonds.
Answer» SOLUTION :BREAKING, FORMATION

Discussion

1170.	A chemical reaction always involves absorption of energy.
Answer» ANSWER :F

Discussion

1171.	A change which is irreversible and leads to formation of new substances.
Answer» SOLUTION :CHEMICAL

Discussion

1172.	A change that occurs after a fixed interval of time.
Answer» SOLUTION :PERIODIC

Discussion

1173.	A building constructed from mortar becomes stronger on long standing. Give a reason.
Answer» SOLUTION :(i) Constituents of mortar. (ii) PURPOSE of mortar in construction. (iii) REACTION between ONE of the components present in mortar with the component present in air. (iv) The percentage abundance of the above component present in air. (v) Relation between the availability of the REACTANT and the time taken for the reaction.

Discussion

1174.	A, B, C, D are four gases. If the order of their critical temperature is as follows D lt B lt C lt A, which of the following gas has the highest boiling point?
Answer» A B C D Answer :A::C

Discussion

1175.	""_(8)X^(16) and ""_(8)X^(17) represent
Answer» Isotones Isobars Isotopes Isosters Answer :C

Discussion

1176.	50 g of oil 'A' and 100 g of oil 'B' are taken in separate containers at same temperature specific heat of oil 'B' is double to that of oil 'A' . Both are heated in such a way that increase in temperature is also same. Calculate the ratio of heat required to be supplied for increasing the temperature .
Answer» `1:2` `1:1` `4:1` `1:4` ANSWER :C::D

Discussion

1177.	2C + ("limited")O_(2) to…………..
Answer» ANSWER :2CO

Discussion

1178.	{:(1."Separating ammonium chloride from salt",(a) "Filtration"),( 2. "Separating paneer from whey",(b) "Fractional distillation"),(3. "Separating flour from bran", (c ) "Centrifugation"),( 4. "Separating butter from milk",(d) "Sublimation"),( 5. "Separating petrol and diesel from crude oil", (e) "Sieving"):}
Answer» Solution :1. d 2. a 3. e 4. c 5. b

Discussion

1179.	{:(1.,"Net result is absorption of energy","a.","Exothermic reaction"),(2.,"Burning is this type of a reaction","b.","Basic oxide"),(3.,"Oxides of metals","c.","Acidic oxides"),(4.,"Oxides of non-metals","d.","Neutral oxide"),(5.,"Water is an example of","e.","Endothermic reaction"):}
Answer» ANSWER :E, a, B, C, d

Discussion

1180.	{:(1.,"Chemical symbol of potassium","(a)","Ca"),(2.,"Chemical symbol of calcium","(b)","Cu"),(3.,"Element with valency 4","(c)",Cu^(+)),(4.,"Element with variable valencies","(d)","K"),(5.,"Cation","(e)","C"):}
Answer» ANSWER :d, a, E, B, C

Discussion

1181.	{:(1."Arrangement of electrons in energy shells", a."Valence shell"),(2."Maximum number of electrons = 18",b."Electronic configuration"),(3."Outermost shell of an atom",c."Valency"),(4."Combining cpacity of the atoms of an element",d."Number of charge it carries"),(5."An element with 8 valence electrons",e."M energy shell"),(6."Valency of a radical",f."Octet configuration"):}
Answer» Answer :1. b 2. e 3. a 4. C 5. d

Discussion

1182.	{:(1." Separating miscible liquids", a." Filtration and evaporation"),(2." Separating immiscible liquids",b." Sedimentation, filtration and evaporation"),(3." Separating "CaCO_(3)" and NaCl",c." Separating funnel"),(4." Separating sand, saw dust and salt",d." Fractional distillation"):}
Answer» Answer :1. d 2. C 3. a 4. b

Discussion

1183.	Match with correct: 1. Mass is neither created nor destroyed. (a) Liquid 2. Definite volume but no fixed shape.(b) atoms and molecules 3. Maximum inter-particle space. (c) Conservation of mass 4. All matter is made up of these. (d) Solid 5. Least kinetic energy. (e) Gas
Answer» SOLUTION :1.c 2. a 3.e 4. B 5.d

Discussion

1184.	{:(1. "Discovered the cathode rays " , (a) "E. Goldstein"), ( 2. "Discovered the protons", (b) "J.J. Thomson" ), (3. "Discovered the neutrons ",(c ) "William Crookes") , (4. "Plum pudding model",(d) "Lord Rutherford" ) , ( 5. "Planetary model of an atom ", (e ) "James Chadwick"):}
Answer» ANSWER :1. C 2. a 3. e 4. b 5. d

Discussion

1185.	______ substance when exposed to moisture dissolve in it.
Answer» ANSWER :DELIQUESCENT

Discussion

1186.	______ solution is more concentrated than saturated solvent.
Answer» ANSWER :SUPER SATURATED

Discussion

1187.	_________ resists fire and can tolerate heat better than other plastics.
Answer» ANSWER :B

Discussion

1188.	_____ replaces, copper from copper sulphate.
Answer» Copper Zinc Sodium Zinc Sulphate Answer :B

Discussion

1189.	"___________" Process is used to extract sulphur from deposits near the earth' s crust
Answer» SOLUTION :SICILIAN

Discussion

1190.	............... method of separation involves both evaporation and condensation.
Answer» SOLUTION :DISTILLATION

Discussion

1191.	............... method is used to separate substances based on their different densities.
Answer» SOLUTION :CENTRIFUGATION

Discussion

1192.	................ method can be used to separate a mixture having components of different sizes.
Answer» SOLUTION :SIEVING

Discussion

1193.	________ is used in the manufacture of black carbon papers.
Answer» SOLUTION :LAMP BLACK

Discussion

1194.	_________ is used for making photographic films.
Answer» `AgNO_(3)` `KNO_(2)` AgO AgCl Answer :C::D

Discussion

1195.	___________is used for extinguishing fires on electrical equipment and inflammable materials like petrol.
Answer» ANSWER :A::B::C::D

Discussion

1196.	______ is used extensively in the manufacture of washing soda
Answer» CARBON dioxide Carbon monoxide METHANE LAMP black Solution :Carbon dioxide is used extensivly in the manufacture of washing soda. `CO_(2)+2NAOH to Na_(2)CO_(3)+H_(2)O`

Discussion

1197.	............... is the method of separating heavier and lighter components of amixture with the help of wind. (sublimation/winnowing)
Answer» SOLUTION :WINNOWING

Discussion

1198.	_____ is stored in kerosene.
Answer» Copper Lead Sodium Iron Answer :C

Discussion

1199.	______ is malleable and ductile.
Answer» Aluminium Carbon Oxygen Sulphur Answer :A

Discussion

1200.	_____ is formed when sulphur dioxide reacts With Water.
Answer» SULPHURIC acid Sulphur Copper sulphate Sulphurous acid Answer :D

Discussion

Explore topic-wise InterviewSolutions in .

A nonmetal X forms two oxides, A and B. The ratio of weight of the element X to the weight of oxygen in A and B is 7 : 20 and 7 : 16 respectively. If the molecular mass of the oxide, A is 1 08, identify A and B.

A neutral atom of an element has a nucleus with nuclear charge 12 times and mass 24 times that ofhydrogen. Calculate the number of electrons, protons and neutronsin its stable positively charged ion.

A mixture of 95% oxygen and 5% CO_(2) is called _____.

A mixture is formed by two kinds of matter, the molecules of which possess only vibratory motion. If the change in solubililty of two substancesin a given solvent differs widely with the change in temperature, how can these twosolids be separted from the solvent?

A mixture consists of various components that are present in a fixed proportion.

A metallic element forms an ion with unit charge. The ion has 10 electrons and 12 neutrons . What is the number of electrons, protons and neutrons in its neutral atom ? Represent the atom with atomic number and mass number.

A metal which is more reactive than calcium.

A hydrocarbon on complete combustion produces176 g of carbon dioxide and 90 g of water. What will x the formula of hydrocarbon be and also give balanced chemical equation of combustion of hydrocarbon?

A gas which is combustible and can support combustion is.

A di-positive ion has an electronic arrangement 2,8,8 . Find out the number of electrons, protons and neutrons in that element if its mass number is 40.

A deliquescent substance does not become sticky in an air tight container . Justify.

(a) Decomposition reactions are always initiated with the supply of energy. Give appropriate reasons. (b) Generally burning or combustion reactions are exothermic Justify.

A compound 'X' made of two non-metals, in a reaction with another non-metal 'Y' gives the hardest substance and carbon monoxide. Identify the compound X and non-metal Y.

A cloudy heterogeneous solution in which the solute particles are visible with the eyes is called.............

A china dish weighs 25 g when empty.When saturated solution of potassium chloride is poured into it at 40^(@)C , the weight of the dish is 63 g . When the solution is evaporated to dryness, the china dish along with crystals weighs 40 g. Find the solubility of potassium chloride at 40^(@)C .

A chemical reaction may show the following characteristics.

A chemical reaction involves ……………. And ……………. Of bonds.

A chemical reaction always involves absorption of energy.

A change which is irreversible and leads to formation of new substances.

A change that occurs after a fixed interval of time.

A building constructed from mortar becomes stronger on long standing. Give a reason.

A, B, C, D are four gases. If the order of their critical temperature is as follows D lt B lt C lt A, which of the following gas has the highest boiling point?

""_(8)X^(16) and ""_(8)X^(17) represent

2C + ("limited")O_(2) to…………..

{:(1.,"Net result is absorption of energy","a.","Exothermic reaction"),(2.,"Burning is this type of a reaction","b.","Basic oxide"),(3.,"Oxides of metals","c.","Acidic oxides"),(4.,"Oxides of non-metals","d.","Neutral oxide"),(5.,"Water is an example of","e.","Endothermic reaction"):}

{:(1.,"Chemical symbol of potassium","(a)","Ca"),(2.,"Chemical symbol of calcium","(b)","Cu"),(3.,"Element with valency 4","(c)",Cu^(+)),(4.,"Element with variable valencies","(d)","K"),(5.,"Cation","(e)","C"):}

{:(1." Separating miscible liquids", a." Filtration and evaporation"),(2." Separating immiscible liquids",b." Sedimentation, filtration and evaporation"),(3." Separating "CaCO_(3)" and NaCl",c." Separating funnel"),(4." Separating sand, saw dust and salt",d." Fractional distillation"):}

Match with correct: 1. Mass is neither created nor destroyed. (a) Liquid 2. Definite volume but no fixed shape.(b) atoms and molecules 3. Maximum inter-particle space. (c) Conservation of mass 4. All matter is made up of these. (d) Solid 5. Least kinetic energy. (e) Gas

{:(1. "Discovered the cathode rays " , (a) "E. Goldstein"), ( 2. "Discovered the protons", (b) "J.J. Thomson" ), (3. "Discovered the neutrons ",(c ) "William Crookes") , (4. "Plum pudding model",(d) "Lord Rutherford" ) , ( 5. "Planetary model of an atom ", (e ) "James Chadwick"):}

______ substance when exposed to moisture dissolve in it.

______ solution is more concentrated than saturated solvent.

_________ resists fire and can tolerate heat better than other plastics.

_____ replaces, copper from copper sulphate.

"___________" Process is used to extract sulphur from deposits near the earth' s crust

............... method of separation involves both evaporation and condensation.

............... method is used to separate substances based on their different densities.

................ method can be used to separate a mixture having components of different sizes.

________ is used in the manufacture of black carbon papers.

_________ is used for making photographic films.

___________is used for extinguishing fires on electrical equipment and inflammable materials like petrol.

______ is used extensively in the manufacture of washing soda

............... is the method of separating heavier and lighter components of amixture with the help of wind. (sublimation/winnowing)

_____ is stored in kerosene.

______ is malleable and ductile.

_____ is formed when sulphur dioxide reacts With Water.