1214 + Interview Questions in Chemistry in Class 8 Page 18 InterviewSolution

851.	Fill in the blanks Bitumen is used in place of ………….. Formetalling of roads.
Answer» ANSWER :COAL TAR

Discussion

852.	Fill in the blanks : _____are a major source of gaseous pollutants like sulphur dioxide andnitrogen dioxide.
Answer» ANSWER :PETROLEUM REFINERIES

Discussion

853.	Fill in the blanks …………….. And ……………. Are obtained rom petroleum.
Answer» ANSWER :PETROL, DIESEL

Discussion

854.	Fill in the blanks : A special type of plastic on which oil and water do not stick is _______
Answer» ANSWER :TEFLON

Discussion

855.	Fill in the blanks : A liquid fuel, used in homes is ________
Answer» ANSWER :A::D

Discussion

856.	Fill In the Blanks : _____ reacts slowly with water.
Answer» ANSWER :IRON

Discussion

857.	Fill in the blanks : _____ leads to an increase in the amount of carbon dioxide in the air.
Answer» ANSWER :DEFORESTATION

Discussion

858.	Fill In the Blanks : _____ is used for wrapping food.
Answer» ANSWER :ALUMINIUM FOIL

Discussion

859.	Fill in the blanks : ________ gets rusted when left exposed to moisture and air.
Answer» ANSWER :IRON

Discussion

860.	Fill in the blanks : _______ can be recycled, reused, coloured, melted, rolled into sheets or made into wires.
Answer» ANSWER :PLASTIC

Discussion

861.	Fill In the Blanks : _____ are both metallic and non-metallic in nature.
Answer» ANSWER :METALLOIDS

Discussion

862.	Fill In the Blanks : _____ and _____ can easily be cut with knife.
Answer» ANSWER :SODIUM; POTASSIUM

Discussion

863.	FeS_(2) on burning in oxygen gives _______.
Answer» SOLUTION :`FEO,SO_(2)`

Discussion

864.	Fe_3O_4+4H_2to3Fe+4H_2O 2Na+Cl_2to2NaCl. Indentify the oxidizing agent in the given reactions.
Answer» SOLUTION :(i) SUBSTANCE which loses OXYGEN (ii) Substance which GAINS the electrons

Discussion

865.	Farmers are advised to grow beans or peas plants in crop rotation. Give reasons in support of your answer.
Answer» Solution :(i) Micro ORGANISM PRESENT in roots ofbean or pea plants. (II) The role of the micro organisms present in beans and pea plants in trapping the aerial nitrogen (iii) Role of nitrogen in the growth of plants.

Discussion

866.	Express the following chemical changes in the form of chemical equations and identify what types of chemical reactions they are. (a)A copper coin is placed in a solution of corrosive sublimate, mercuric chloride. The products obtained are cupric chloride and mercury. (b) A piece of (a) sulphur, (b) charcoal burns vigorously when dropped jn molten potassium nitrate, because potassium nitrate decomposes to form potassimn uitrite and oxygen and this oxygen helps to burn charcoal and sulphur giving out carbon dioxide and sulphurdioxide respectively. (c) Aqueous anmonium hydroxide solution is made to react with aqueous copper sulphate solution and a bluish white precipitate of cupric hydroxide and ammonium sulphate are formed.
Answer» Solution :(a) `Cu+HgCl_2toCuCl_2+Hg` Copper DISPLACES mercury from mercuric chloride and forms cupric chloride and mercury. This is a displacement reaction. (b)`2KNO_3to2KNO_2+O_2to(1)` `S+O_2toSO_2 to(2)` `C+O_2toCO_2to(3)` This first reaction repersents to FORM POTASSIUM nitrite and oxygen. Oxygen LIBERATED helps burn sulphur and charcoal to give sulphuric dioxide and carbon dioxide as given in the reactions (2) and (3). Reaction (1) is DECOMPOSITION reaction reactions. (c) `2NH_2OH+CuSO_4toCU(OH)_2downarrow+(NH_4)_2SO_4`

Discussion

867.	Explain with equations the electrical process for the extraction of phosphorous
Answer» Solution :(i) Raw materials. (ii) Electric FURNACE SET up. (iii) Reactions involved. (IV) Puriflcation

Discussion

868.	Explain why the snow on ht mountain peaks does not melt at a temperature slightly above 0^(@)C.
Answer» Solution :The atmospheric pressure on the mountain peaks is LOW. As ICE contracts on MELTING, with the decrease in pressure its melting point INCREASES. Thus, the snow does not MELT slightly above `0^(@)C`.

Discussion

869.	Explain why the following is made of thermosetting plastics. Saucepan handles.
Answer» ANSWER :Saucepan HANDLES are made of bakelite, a type of THERMOSETTING plastics. As bakelite is a poor conductor of HEAT.

Discussion

870.	Explain why the following is made of thermosetting plastics. Electric plugs/switches/plug boards.
Answer» Answer :Bakelite, a type of thermosetting plastic, is a conductor of heat and ELECTRICITY. Hence, ELECTRIC plugs, switches, plug boards, etc. are made from thermosetting PLASTICS.

Discussion

871.	Explain why the atmospheric pressure changes with altitude?
Answer» SOLUTION :(i) COMPOSITION of air (II) CHANGE in density of air.

Discussion

872.	Explain why temperature in the coastal region is moderate throughout the year.
Answer» Solution :In coastal regionsk the amount of the water is more and the specific heat of water is much higher than of the LAND. Hence a MAJOR part of heat coming from the sun is ABSORBED by water the increase of temperature of water is less because of its higg specific heat. Hence the temperature of the land does not change much.

Discussion

873.	Explain why some fibres are called synthetic.
Answer» ANSWER :Some FIBRES are called synthetic or artifician fibres because they are not obtained from natural source like cellulose, silkworm, WOOD PULP, etc.

Discussion

874.	Explain why plastic containers are favoured for storing food.
Answer» Answer :PLASTIC containers are favoured for STORING food due to the following advantages:(i) They are light in WEIGHT.(ii) They are easy to HANDLE.

Discussion

875.	Explain why CuSO_(4), 5H_(2)O can be dehydrated by reducing the external pressure at room temperature .
Answer» Solution :(i) VAPOUR pressure of `CuSO_(4).5H_(2)O`. (ii) COMPARISION between atmospheric pressure and vapour pressure of HYDRATED copper SULPHATE. (iii) Changes in hydrated `CuSO_(4)` at lower pressure conditions.

Discussion

876.	Explain why cobalt choride acts as a humidity indicator.
Answer» Solution :(i) Changes in PHYSICAL property. (ii) Colour of cobalt chloride. (iii) Vapour pressure of cobalt chloride. (iv) Changes in cobalt chloride in humid ATMOSPHERE. (V) EFFECT on colour of`CoCl_(2)` DUE to these changes.

Discussion

877.	Explain various types of chemical fertilizers with examples
Answer» SOLUTION :Definition of chemical FERTILIZERS. (II) Nitrogenous fertilizers (iii) Phospatatic fertilizers. (iv) Potash fertilizers

Discussion

878.	Explain Thomson's atomic model. What are the drawbacks of this model ?
Answer» Solution :Model: (i) SPACE (ii) Distribution of POSITIVE charge (iii) EMBEDDED ELECTRONS

Discussion

879.	Explain the working principal of scrubber.
Answer» Solution :(i) Substances used in scrubber. (II) Chemical nature of the SUBSTANCE used in the scrubber. (iii) PROPERTY of the kind of impurity that is remvoved by scrubber. (IV) Reactions that take PLACE between the impurities and the substance used in the scrubber.

Discussion

880.	Explain the working of the two types of fire extinguishers.
Answer» SOLUTION :(i) Principle (II) Components (iii) REACTIONS (IV) Limitations.

Discussion

881.	Explain the structure of graphite.
Answer» SOLUTION :LAYERED STRUCTURE of hexagonal RINGS ARRANGED parallel to each other.

Discussion

882.	Explain the separation of charocoal from sulphur.
Answer» SOLUTION :SOLUBILITY of ONE COMPONENT.

Discussion

883.	Explain the role of dry ice in the occurrence of artificial rain.
Answer» SOLUTION :(i) Reason behind the OCCURRENCE of natural rain. (ii) Composition of dry ice. (iii) Condition required for the formation of CLOUDS. (IV) Type of PHASE transition that takes place in dry ice. (v) Effect of the above phase transition on the temperature of the surroundings.

Discussion

884.	Explain the role of baking soda as a leavening agent and as an antacid ?
Answer» Solution :(i) Chemical PROPERTY of baking SODA. (ii) Reaction of baking soda with other component present in baking powder. (iii) Physical state of the PRODUCTS formed. (iv) Effect of the physical state of the products on bakery products. (v) Reaction of baking soda with the excess acid PRODUCED in the stomach. (vi) Nature of the reaction.

Discussion

885.	Explain the reducing property of wood charcoal.
Answer» Solution :When WOOD charcoal heated with oxides of less ACTIVE metal they get REDUCED to FREE METALS.

Discussion

886.	Explain the reaction of chlorine with magnesium
Answer» SOLUTION :`Mg+CL_2rarrMgCL_2`

Discussion

887.	Explain the reaction of chlorine gas with turpentine.
Answer» Solution :(1) Formula of TURPENTINE. (II) Conditions. (iii) PRODUCTS formed

Discussion

888.	Explain the procedure for separation of sand water into sand and water.
Answer» SOLUTION :SAND HEAVIER than WATER.

Discussion

889.	Explain the principle of atomic hydrogen torch.
Answer» SOLUTION :CHEMICAL REACTIONS INVOLVED

Discussion

890.	Explain the principal of the working fo smoke precipitators.
Answer» Solution :(i) REACTIVITY of gaseous species at electrodes. (ii) COMPONENTS present in smoke. (iii) VOLTAGE in smoke precipitators. (iv) CHANGE in components of smoke.

Discussion

891.	Explain the principal involved in the liquefaction of air.
Answer» Solution :(i) Result of sudden expansion of gases. (ii) Temperature required for air to liqnefy. (iii) CONDITIONS to attain the LIQUEFACTION. (IV) Forces between MOLECULES. (V) Effect of temperature on movement of molecules.

Discussion

892.	Explain the methods by which the constituents in gunpowder can be separated.
Answer» SOLUTION :(i) Composition of gun POWDER. (II) Identification of SUITABLE solvents. (III) Extraction of the components from respective solutions.

Discussion

893.	Explain the method by which Cl_(4),H_(2)O and ethyl alcohol mixture can be separated.
Answer» Solution :(i) Miscible and immiscible liquids. (ii) The SEPARATION of miscible and immiscible liquids (iii) Comparison of the physical PROPERTIES of liquid. (iv) SUITABLE separation procedure BASED on physical properties

Discussion

894.	Explain the manufacture of graphite by Acheson process.
Answer» Solution :(i) Raw MATERIAL (ii) SET up (III) CONDITIONS.

Discussion

895.	Explain the law of multiple proportions with an example .
Answer» Solution :(i) Elements combine in DIFFERENT ratios to give defferent products. (ii)Simple integral ratio. (III)Ratio of OXYGEN to NITROGEN in `N_2O, NO,NO_2`.

Discussion

896.	Explain the law of definite proportions with an example.
Answer» SOLUTION :(i) ELEMENTS coinbine in a fixed ratio of their WEIGHTS. (ii) Formation of CARBON dioxide from different sources.

Discussion

897.	Explain the general methods of preparation of hydrogen giving one example each . Among these, which method is preferred for laboratory preparation and why ?
Answer» Solution :(i) Method (II) CHEMICAL equations (iii) Observations (IV) REACTIVITY of reactants

Discussion

898.	Explain the effect of temperature on the electrical conductivity of metals.
Answer» SOLUTION :(i) The CAUSE of ELECTRICAL conductivity in metals. (ii) The effect of temperature on KINETIC energy of METAL atoms. (iii) The effect of temperature on direction of species, conducting electricity. (iv) Effect of these on conductivity.

Discussion

899.	Explain the construction and working of the (i) Mercury barometer (ii) Aneriod barometer
Answer» SOLUTION :(i) Components (ii) Principle (III) CONSTRUCTION (IV) WORKING

Discussion

900.	Explain the construction and working of 3 Nelson cell.
Answer» SOLUTION :(i) Perforated steel Utube. (ii) Brine solution. (III) Graphite rod (iv) Cathode, anode. (v) ELECTROLYTIC dissociation of NaCl. (vi) Liberation of chlorine gas. (vii) Liberation of hydrogen gas. (viii) FORMATION of NaOH.

Discussion

Explore topic-wise InterviewSolutions in .

Fill in the blanks Bitumen is used in place of ………….. Formetalling of roads.

Fill in the blanks : _____are a major source of gaseous pollutants like sulphur dioxide andnitrogen dioxide.

Fill in the blanks …………….. And ……………. Are obtained rom petroleum.

Fill in the blanks : A special type of plastic on which oil and water do not stick is _______

Fill in the blanks : A liquid fuel, used in homes is ________

Fill In the Blanks : _____ reacts slowly with water.

Fill in the blanks : _____ leads to an increase in the amount of carbon dioxide in the air.

Fill In the Blanks : _____ is used for wrapping food.

Fill in the blanks : ________ gets rusted when left exposed to moisture and air.

Fill in the blanks : _______ can be recycled, reused, coloured, melted, rolled into sheets or made into wires.

Fill In the Blanks : _____ are both metallic and non-metallic in nature.

Fill In the Blanks : _____ and _____ can easily be cut with knife.

FeS_(2) on burning in oxygen gives _______.

Fe_3O_4+4H_2to3Fe+4H_2O 2Na+Cl_2to2NaCl. Indentify the oxidizing agent in the given reactions.

Farmers are advised to grow beans or peas plants in crop rotation. Give reasons in support of your answer.

Explain with equations the electrical process for the extraction of phosphorous

Explain why the snow on ht mountain peaks does not melt at a temperature slightly above 0^(@)C.

Explain why the following is made of thermosetting plastics. Saucepan handles.

Explain why the following is made of thermosetting plastics. Electric plugs/switches/plug boards.

Explain why the atmospheric pressure changes with altitude?

Explain why temperature in the coastal region is moderate throughout the year.

Explain why some fibres are called synthetic.

Explain why plastic containers are favoured for storing food.

Explain why CuSO_(4), 5H_(2)O can be dehydrated by reducing the external pressure at room temperature .

Explain why cobalt choride acts as a humidity indicator.

Explain various types of chemical fertilizers with examples

Explain Thomson's atomic model. What are the drawbacks of this model ?

Explain the working principal of scrubber.

Explain the working of the two types of fire extinguishers.

Explain the structure of graphite.

Explain the separation of charocoal from sulphur.

Explain the role of dry ice in the occurrence of artificial rain.

Explain the role of baking soda as a leavening agent and as an antacid ?

Explain the reducing property of wood charcoal.

Explain the reaction of chlorine with magnesium

Explain the reaction of chlorine gas with turpentine.

Explain the procedure for separation of sand water into sand and water.

Explain the principle of atomic hydrogen torch.

Explain the principal of the working fo smoke precipitators.

Explain the principal involved in the liquefaction of air.

Explain the methods by which the constituents in gunpowder can be separated.

Explain the method by which Cl_(4),H_(2)O and ethyl alcohol mixture can be separated.

Explain the manufacture of graphite by Acheson process.

Explain the law of multiple proportions with an example .

Explain the law of definite proportions with an example.

Explain the general methods of preparation of hydrogen giving one example each . Among these, which method is preferred for laboratory preparation and why ?

Explain the effect of temperature on the electrical conductivity of metals.

Explain the construction and working of the (i) Mercury barometer (ii) Aneriod barometer

Explain the construction and working of 3 Nelson cell.

Fill In the Blanks : _ and _ can easily be cut with knife.