908 + Interview Questions in Chemistry in Class 7

1.	A group of students went for an excursion to Shimla in the month of November. A science teacher also accompanied them. There the temperature fell to -10^(@)C. They took some ice cubes and subjected them to heating while keeping a thermometer in the container. The students monitored the readings of thermometer till the entire ice melted into water. All of them went to their science teacher and showed him their observations. He asked them to discuss among themselves and give a proper justification for the observations on the readings at various stages.
Answer» Solution :The heat energy supplied is completely utilized to convert ice into liquid WATER. As a RESULT, thermometer does not register any rise in temperature till all the ice CUBES melts.

Discussion

2.	A group of students accompanied by their science teacher went trekking. After reaching the top of the hill they felt hungry. The Teacher told them that they would have to bear the hunger as cooking of food is slow and takes a longer time at the top of the hill. The students wanted to known the reason for the above fact. The Teacher explained the reason for the above fact till the food was cooked. Can you predict the explanation given by the teacher?
Answer» Solution :With the INCREASE in altitude the ATMOSPHERIC PRESSURE decreases. Boiling point of WATER is DIRECTLY proportional to the atmosphere pressure. Hence boiling point of water decreases at the top of a hill and cooking takes a longer period of time.

Discussion

3.	A gaseous element 'X' is used in the manufacture of bleaching powder. On reaction withhydrogen, 'X' forms a substance 'Y' which after dissolution in water is usedto clean metal surfaces. Identify X and Y. Justify.
Answer» Solution :The element cholrine is USED in the MANUFACTURE of bleaching power. It reacts with hydrogen to form hydrogen CHLORIDE which dissolves in WATER to gives hydrochloric acid . It is is used to clean the METAL surfaces. So 'X' is chlorine and 'Y' is hydrochloride which on dissolution in water gives hydrochloricacid. Metal surfaces have coating of metal oxides andhydrochloric acid can react with the metal oxides and removes the coating.

Discussion

4.	A gas X when passed through blue litmus solution turns it red. Another gas Y when through either blue litmus or red litmus does not change the colour of the litmus. Identigy the true statement regarding X and Y.
Answer» X is BASIC while Y is neutral. Y is neutral while X is acidic. Y is basic while X is acidic. Y is acidic while X is neutral. Solution :X is an acidic GAS since it changes blue litmus RED. Y is neutral since it does RESPOND to EITHER red or blue litmus test.

Discussion

5.	A gas 'X' when passed through blue litmus solution turn it red. Another gas 'Y' when passed through either blue litmus or red litmus does not change the colour of the litmus. Identigy the trun statement regarding X and Y.
Answer» X is basic while Y is NEUTRAL. Y is neutral while X is ACIDIC. Y is basic while X is acidic. Y is acidic while X is neutral. Solution :X' is anacidic gas since it CHANGES blue litmus red. 'Y' is neutral since it does not RESPOND to either red or blue litmus.

Discussion

6.	A gas of collected by the upward displacement of air but cannotbe collected either downward or upward displacement of water. Identify the probable characteristics of the gas.
Answer» It's HEAVIES than air and insoluble in WATER. It's lighter than air and it is HIGHLY soluble in water. It is heavier than air and it is highly soluble in water. It is lighter than air and water. Solution :"X" is highly soluble in water. HENCE it cannot be colected by water. It is collected by the UPWARD displacement of air as it is heavier then air.

Discussion

7.	A gas is collected by the upward displacement of air but cannot collected by downward displacement of water. Identify the probable characteristics of the gas.
Answer» It is heavier than air and insoluble in water. It's VAPOUR DENSITY is equaol to air and it is highly SOLUBLE in water. It is heavier than air and it is highly soluble water. It is lighter than air and water. Solution :The gas is highly soluble in water. Hence is cannot b COLLECTED by the downward displacement of water. It is collected by the UPWARD displacement of air as it is heavier than air.

Discussion

8.	A form of which of the following non-metals is the hardest substance ?
Answer» Phosphorus Sulphur Iodine CARBON Solution :An ALLOTROPE of carbon, DIAMOND is the HARDEST SUBSTANCE.

Discussion

9.	A form of which of the following non-metal is the hardest substance ?
Answer» Phosphorus Sulphur Iodine Carbon Solution :An ALLOTROPE of carbon, NAMELY diamond is the HARDEST substance.

Discussion

10.	(a) Explain the different causes of depletion of water table. (b) What steps should be taken in day to day life to prevent depletion of water table?
Answer» Solution :(a) Causes of DEPLETION 1. Scanty rainfall or draught conditions: As long as there is balance between the usage of underground water and its replenishment by rainfall, there is no question of depletion. But, during long periods of scanty rainfall or in the absence of rainfall, this balance is disturbed.Usage of underground water continues more or less at the same level while its replenishment becomes very less or almost nil. This results in the depletion of water table. 2. Deforestation: Big trees in dense forests bind the soil particles through the roots. As a result they help in reducing the water flow and help in the seepage of rain water through the soil. Deforestation results in reduction in forest area which allows the rain water flow RAPIDLY into large water bodies. Seepage becomes less thereby leading to imbalance in the replenishment of underground water. Moreover, trees are one of the sources of water vapour which condenses to form clouds and results in rain. 3. Increasing population: Increasing population which forces increased demand for construction This leads to depletion of water table by decreasing the area of seepage and increasing the demand for water. 4. Increasing industrialization: Every industry requires water for usage in various ways. Increase in number of industries leads to tremendous increase in usage of water which does not match with the rate of replenishment. Thus, it also eventually leads to the depletion of water table. 5. Increased agricultural activities: Due to erratic rainfall, the canal irrigation becomes rather impractical in certain AREAS. As a result, agriculture mostly depends on ground water for irrigation. The increased demand for agriculture results in the depletion of water table. the above activities in the long run lead to tremendous depletion of ground water level and eventually to acute shortage of water. (b) Water being the most precious and essential natural resource and the percentage of available water being less should be used judiciously. Several steps should be taken in day to day life both by the citizens as well as authorities for preventing depletion of water table. 1. Water management as such involves two major aspects. One is prevention of wastage of water by providing water supply through pipes without leakage. At the individual level, minimizing the wastage in daily activities is an important step. Another aspect is utilizing the rain water to recharge the ground water. This is called water harvesting or rain water harvesting. This can be done by installing water harvesting systems in the households. 2. Adoption of drip irrigation system in agriculture can also effectively help to minimize the usage of water in agricultural practices. In drip irrigation, water is supplied to the plants by using narrow tubings which deliver water directly at the base of plant. Irrigation by CLOSED pipes instead of open canals can be of help in this direction since it reduces the loss of water by evaporation. 3. In regions with scanty rainfall, a substance called cetyl ALCOHOL is sprayed on the water in reservoirs meant for storage of large quantities of water. This reduces rate of evaporation of water. 4. Growing some plants under plastic covers also minimizes water loss as the water vapour condenses on the inner surface of plastic cover and is given back to soil.

Discussion

11.	A drop of water contains_________
Answer» 2 atoms of hydrogen and one ATOM of oxygen 1 molecules of hydrogen and one atom of oxygen millions of molecules of WATER one molecule of hydrogen and one molecule of oxygen Solution :A DROP of water contains. Millions of molecules of water

Discussion

12.	A divalent metal salt X, which contributes to hardness of water, combines with washing soda and forms an insoluble salt Y and common salt. Salt Y is also used for the laboratory preparation of CO_(2). Identify X and Y respectively.
Answer» `CaSO_(4), CaCO_(3)` `MgSO_(4), MgCO_(3)` `CaCl_(2), CaCO_(3)` `MgCl_(2), MgCO_(3)` Solution :Divalent metal salt X which contributes to hardness of water is `CaCl_(2)` which combines with `Na_(2)CO_(3)`gives insoluble salt Y that is calcium CARBONATE and sodium chloride. `CaCl_(2)+Na_(2)CO_(3)rarrCaCO_(3)darr+2NaCl`

Discussion

13.	A combines with B to form C and D. A and D are major contributors for global warming and both are carbon compounds. B is a supporter of combustion. Magnesium burns in the presence of B with a dazzling white flame and forms a product X which is basic in nature. With C, X forms a corresponding compound which turns red litmus paper to blue. Give the respective chemical reaction involved.
Answer» Solution :A is METHANE, B is oxygen, C is water vapour and D is carbon dioxide. Methane and `CO_(2)` contribute to green house effect and both are carbon COMPOUNDS. Oxygen combines with magnesium produces megnesium oxide with DAZZLING white flame. `2Mg+O_(2)to1MgO`,MgO is basic in nature. `MgO+H_(2)OtoMg(OH)_(2)`. Magnesium hydroxide is base which trurns red litmus blue.

Discussion

14.	A chemistryteacher was teaching polymers in a class. He said that thogh bakelite and polyethylene belong to polymer family, only bakelite is used for making electrical insulators or handles of kitchenware. Why can not polyethyene be used for theabove purpose?
Answer» SOLUTION :POLYTHENE and bakelite are the POLYMERS and have a lot of applications in daily LIFE. Since polythene is a thermoplastic ( which melts on heating ) can not be USES for making electrical insulators or handles. Bakelite can be used for these purposes as it is a thermosetting polymer ( once set into hard mass can not be remelted ).

Discussion

15.	(a) Ca_(3)(PO_(4))_(2) (b) Ca(OH)Cl (c) CaOCl_(2) (d) K_(4)[Fe(CN)6] Arrange the above salts in the order of complex salt, basic salt, normal salt and mixed salts respectively.
Answer» dbca bdca DBAC bdac Solution :dbac. (i) `K_(4)[Fe(CN)_(6)]` (ii) Ca(OH)CI (iii) `Ca_(3)(PO_(4))_(2)` (iv) `CaOCI_(2)`

Discussion

16.	A burning splinter gets extinguished in an atmosphere of CO_(2). Identify the substance which continues to burn in an atmosphere of CO_(2).
Answer» COKE Magnesium Sulphur Phosphorus Solution :Magnesium BURN in an ATMOSPHERE of `CO_(2)`.

Discussion

17.	A+BCtoAC +BIn the above equation , compare the reactivities of A and B.
Answer» SOLUTION :A is more REACTIVE than B.

Discussion

18.	A, B, C and D are four layers of atmosphere A helps in long distance radio communications. It layer B most of weather phenomena take place. The pollutants relesed from air coonditioners and aerosols deplete layer 'D' which also gets depleted by nitrous oxide. Meteorites burn up in layer C. Identify the layers A, B, C and D, arrange them in increasing order of hight from the surface of earth.
Answer» Solution :A = Ionosphere or THERMOSPHERE, B = Troposphere, C = Mesosphere, D = Stratosphere. Increasing order of FIVE layers as per ALTITUDE from the surface of earth are `B lt D lt C lt A`.

Discussion

19.	2KMnO_(4)+H_(2)SO_(4)+H_(2)C_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+10CO_(2)+8H_(2)OPotassium permanganate oxidizes oxalic acid in acidic medium as per the above chemial reaction . IdentifythecoefficientsofH_(2)SO_(4) and H_(2)C_(2)O_(4)in the above equation.
Answer» 3 , 5 4 , 4 5 , 3 4 , 2 Solution :`2KMnO_(4)+3H_(2)SO_(4)+5H_(2)C_(2)O_(4)to2MnSO_(4)+10CO_(2)+8H_(2)O`.

Discussion

20.	2KMnO_(4)+H_(2)C_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+10CO_(2)+8H_(2)O.ltvrgtPotassium permanganate oxidises oxalic acid in acidic medium as per the above chemical reaction. Identifythe coefficient of H_(2)SO_(4)in the above equatio.
Answer» 3 4 5 2 Solution :`2KMnO_(4)+3H_(2)SO_(4)+5H_(2)C_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+10CO_(2)+8H_(2)O`.

Discussion

21.	2HOCl to2HCl+O_(2)is a ____________ decomposition reaction.
Answer» SOLUTION :photolytic `2HOCl to2HCl+O_(2)`is photolytic DECOMPOSITION REACTION.

Discussion

22.	1 g of water at 100^(@)C on heating forms 1g of steam at the same temperature by absorbing ______ cal of energy.
Answer» Solution :1 g of water at `100^(@)C` on heating forms 1 g of STEAM at the same TEMPERATURE by absorbing 540 cal of energy.

Discussion

23.	1g of pure water at 4^(@)C occupies a volume of ______.
Answer» Solution :1 g of PURE water at `4^(@)C` occupies a VOLUME of 1 CC.

Discussion

24.	(1) By using moist blue litmus paper classify the following compounds given below as acids and bases Ca(OH)_(2), H_(2)SO_(4), CH_(3)COOH, NaOH, KOH, Mg(OH)_(2), HNO_(3), NH_(4)OH (2) Mention the acidic or basic or neutral nature of solutions by using (a) litmus (b) methyl orange (c) phenolphthalein indicators.
Answer» Solution :(a) `{:("COMPOUNDS","Colour of blue litmus","NATURE of substance"),(Ca(OH)_(2),"No CHANGES","basic"),(H_(2)SO_(4),"CHANGE to red","acidic"),(CH_(3)COOH,"change to red","acidic"),(NaOH,"no change","basic"),(KOH,"no change","basic"),("Mg"(OH)_(2),"no change","basic"),(HNO_(3),"change to red","acidic"),(NH_(4)OH,"no change","basic"):}` ltBrgt (b) `{:("Indicators","Acidic","Basic","NEUTRAL"),("Litmus","Red","Blue","No change in colour"),("Methyl orange","Yellow","Pink","No change"),("Phenolphthalein","Colourless","Pink","No change"):}`

Discussion

25.	______ volume(s) of hydrogen and ______ volume(s) of oxygen under similar conditions of temperature and pressure combine to give two volumes of water.
Answer» Solution :Two volumes of HYDROGEN and one volume of oxygen under similar CONDITIONS of temperature and PRESSURE combine to GIVE two volume of water.

Discussion

26.	_________ state of matter is incompressible.
Answer» SOLUTION :Solid Solid Solid state is INCOMPRESSIBLE as the FORCE of attraction is STRONG and intermolecular space is less.

Discussion

27.	________ show the properties of metals and non-metals.
Answer» SOLUTION :Matalloids METALLOIDS show the properties of both metals and NON metals.

Discussion

28.	______ on hydrolysis gives a strong acid.
Answer» Sulphur dioxide CARBON dioxide Sulphur trioxide Nitrogen dioxide Solution :`SO_(3)` of hydrolysis GIVES `H_(2)SO_(4)` which is a strong acid `SO_(3) + H_(2)O rarr H_(2)SO_(4)`

Discussion

29.	……….. Is used in the refrigeration of sea food.
Answer» Chlorofluoro carbons DRY ICE Carbon dioxide gas Inert gases Solution :Dry ice is used in the refrigeration of SEA FOOD.

Discussion

30.	…………… is used in advertisment glow tubes.
Answer» NEON Helium Argon Nitrogen Solution :Neon is USED in advertisemint GLOW TUBES

Discussion

31.	_________ is used for filling weather observation balloons.
Answer» SOLUTION :Helium Helium is used for filling WEATHER observation BALLOONS.

Discussion

32.	………………. Is used for burning fuel in the rockets and space ships.
Answer» Solution :LIQUID OXYGEN is USED for BURNING fuels in rockets and SPACE ships.

Discussion

33.	_______ is used as one of the raw materials for making soft soap.
Answer» Sodium CARBONATE Alcohol Potassium hydroxide FINELY GROUND pumice stone Solution :Potassium hydroxide is USED as one of the RAW materials for making soft soap.

Discussion

34.	__________ is used as fuse wire inthermite welding.
Answer» Solution :Magnesium Magnesium is used as FUSE wires in THERMITE WELDING.

Discussion

35.	………. Is used as catalyst in the hydrogenation of oil.
Answer» SOLUTION :NICKEL is USED as CATALYST in the hyrogention of OIL.

Discussion

36.	……… is used as a supporter of combustion in rockets ans space ships.
Answer» Liquid hydrogen Liquid oxygen Coke Liquid carbon dioxide Solution :Liquid oxygen is used as a supporter of combustion in ROCKETS ANS SPACE ships.

Discussion

37.	___________ is used as a solid lubricant for machine parts.
Answer» Solution :GRAPHITE Graphite is USED as a SOLID LUBRICANT for machine PARTS.

Discussion

38.	………….. Is used as a recket fuel.
Answer» SOLUTION :LIQUID hydrogenis USED as a ROCKET FUEL.

Discussion

39.	________ is the suffix used while naming the salt of a metal with lower valency.
Answer» Solution :`-OUS` ` -'ous'` issuffix used to NAME the salt of the corresponding metal with lower valency.

Discussion

40.	…………. Is the process of mixing of a metal or nonmetal a homegenous mixture
Answer» ALLOYING Electroplatin Tinning Galvanization Solution :Alloying is the PROCESS of MIXING a METAL with metal of non-metal to form a homogenous mixture.

Discussion

41.	___ is the non-metal which is a good conductor of electricity.
Answer» SOLUTION :GRAPHITE Graphite is the nonmental which is a GOOD CONDUCTOR of ELECTRICITY.

Discussion

42.	……….. Is the most abundant in earth's crust.
Answer» Si AI `O_(2)` `Fe` Solution :Oxygen is the most ABUNDENT ELEMENT in earth's CRUST.

Discussion

43.	_________ is the least reactive metal which is used as a catalyst.
Answer» SOLUTION :PLATINUM Platinum is the least REACTIVE metal which is used as a CATALYST.

Discussion

44.	………. Is present in sun's atmosphere up to 1.1%
Answer» SOLUTION :HYDROGEN particles HELPS in the FORMATION of cloud.

Discussion

45.	__________ is an example of medicine extracted from the bark of a plant.
Answer» Solution :QUININE Quinine is an EXAMPLE of MEDICINE extracted from thebark of a PLANT.

Discussion

46.	______ is added to prevent the evaporation of water.
Answer» Solution :Cetyl alcohol is ADDED to PREVENT the EVAPORATION of water.

Discussion

47.	_________ is a surface phenomenon whereas boiling is a ________ .
Answer» SOLUTION :Evaporation, BULK phenomenon Evaporation is a SURFACE phenomenon WHEREAS BOILING is a bulk phenomenon.

Discussion

48.	________ is a lustrous non-metal.
Answer» SOLUTION :IODINE Iodine is a LUSTROUS NON METAL.

Discussion

49.	________ in humidity increases rate of evaporation.
Answer» SOLUTION :Decrease Decrease in humidity increases the RATE of evaporation.

Discussion

50.	______ hardness is removed by Clark's method.
Answer» Solution : TEMPORARY HARDNESS is removed by CLARK's method.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

A gaseous element 'X' is used in the manufacture of bleaching powder. On reaction withhydrogen, 'X' forms a substance 'Y' which after dissolution in water is usedto clean metal surfaces. Identify X and Y. Justify.

A gas X when passed through blue litmus solution turns it red. Another gas Y when through either blue litmus or red litmus does not change the colour of the litmus. Identigy the true statement regarding X and Y.

A gas 'X' when passed through blue litmus solution turn it red. Another gas 'Y' when passed through either blue litmus or red litmus does not change the colour of the litmus. Identigy the trun statement regarding X and Y.

A gas of collected by the upward displacement of air but cannotbe collected either downward or upward displacement of water. Identify the probable characteristics of the gas.

A gas is collected by the upward displacement of air but cannot collected by downward displacement of water. Identify the probable characteristics of the gas.

A form of which of the following non-metals is the hardest substance ?

A form of which of the following non-metal is the hardest substance ?

(a) Explain the different causes of depletion of water table. (b) What steps should be taken in day to day life to prevent depletion of water table?

A drop of water contains_________

A divalent metal salt X, which contributes to hardness of water, combines with washing soda and forms an insoluble salt Y and common salt. Salt Y is also used for the laboratory preparation of CO_(2). Identify X and Y respectively.

A chemistryteacher was teaching polymers in a class. He said that thogh bakelite and polyethylene belong to polymer family, only bakelite is used for making electrical insulators or handles of kitchenware. Why can not polyethyene be used for theabove purpose?

(a) Ca_(3)(PO_(4))_(2) (b) Ca(OH)Cl (c) CaOCl_(2) (d) K_(4)[Fe(CN)6] Arrange the above salts in the order of complex salt, basic salt, normal salt and mixed salts respectively.

A burning splinter gets extinguished in an atmosphere of CO_(2). Identify the substance which continues to burn in an atmosphere of CO_(2).

A+BCtoAC +BIn the above equation , compare the reactivities of A and B.

2KMnO_(4)+H_(2)SO_(4)+H_(2)C_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+10CO_(2)+8H_(2)OPotassium permanganate oxidizes oxalic acid in acidic medium as per the above chemial reaction . IdentifythecoefficientsofH_(2)SO_(4) and H_(2)C_(2)O_(4)in the above equation.

2KMnO_(4)+H_(2)C_(2)O_(4)toK_(2)SO_(4)+2MnSO_(4)+10CO_(2)+8H_(2)O.ltvrgtPotassium permanganate oxidises oxalic acid in acidic medium as per the above chemical reaction. Identifythe coefficient of H_(2)SO_(4)in the above equatio.

2HOCl to2HCl+O_(2)is a ____________ decomposition reaction.

1 g of water at 100^(@)C on heating forms 1g of steam at the same temperature by absorbing ______ cal of energy.

1g of pure water at 4^(@)C occupies a volume of ______.

______ volume(s) of hydrogen and ______ volume(s) of oxygen under similar conditions of temperature and pressure combine to give two volumes of water.

_________ state of matter is incompressible.

________ show the properties of metals and non-metals.

______ on hydrolysis gives a strong acid.

……….. Is used in the refrigeration of sea food.

…………… is used in advertisment glow tubes.

_________ is used for filling weather observation balloons.

………………. Is used for burning fuel in the rockets and space ships.

_______ is used as one of the raw materials for making soft soap.

__________ is used as fuse wire inthermite welding.

………. Is used as catalyst in the hydrogenation of oil.

……… is used as a supporter of combustion in rockets ans space ships.

___________ is used as a solid lubricant for machine parts.

………….. Is used as a recket fuel.

________ is the suffix used while naming the salt of a metal with lower valency.

…………. Is the process of mixing of a metal or nonmetal a homegenous mixture

___ is the non-metal which is a good conductor of electricity.

……….. Is the most abundant in earth's crust.

_________ is the least reactive metal which is used as a catalyst.

………. Is present in sun's atmosphere up to 1.1%

__________ is an example of medicine extracted from the bark of a plant.

______ is added to prevent the evaporation of water.

_________ is a surface phenomenon whereas boiling is a ________ .

________ is a lustrous non-metal.

________ in humidity increases rate of evaporation.

______ hardness is removed by Clark's method.

volume(s) of hydrogen and volume(s) of oxygen under similar conditions of temperature and pressure combine to give two volumes of water.

_ is a surface phenomenon whereas boiling is a .