908 + Interview Questions in Chemistry in Class 7

1.	Small water droplets associated with dust particles to form larger aggregates called ______
Answer» Solution :SMALL WATER droplets ASSOCIATED with the dust PARTICLES form larger AGGREGATES called micelles.

Discussion

2.	SI unit of atmospheric pressure is
Answer» NEWTON PASCAL Joule kg/m Solution :SI UNIT of atmospheic PRESSURE is Pascal.

Discussion

3.	Shakti along with his parents was going to the reilway station by an auto to catch a train. Shakti's father was recollecting his childhood days and said that in those days, autos were run with petrol only. His mother added that diesel was used to run autos in later days. Shakthi said that nowadays, autos are preferably run with CNG, Shakti questioned his father regarding the advantage of CNG over petrol and diesel. What was his father's explanation ?
Answer» Solution :CNG does not produce any HARMFUL GASES and THUS it reduces the maintenance cost and it a clean fuel. While petrol and DIESEL CONTAIN N and S which upon combustion produce `NO_(2)" and "SO_(2)` respectively. These lead to acid rain. Hence CNG can be a substitute for petrol and diesel.

Discussion

4.	Separation of sawdust from water, can be carried out by the following steps given below. Arrange them in a proper sequence. (a) The mixture is poured gently in to the filter cone and collected into another beaker which is called filtrate. (b) A mixture of saw dust and water is taken in a beaker (c ) A filter paper is folded in the form of a cone and fitted into a funnel by moistening it with few drops of water (d) solid retained on the filter paper is called residue.
Answer» cabd abcd cdba bcad Solution :(i) A mixture of saw dust and water is taken is taken in a beaker (ii) A filter PAPER is FOLDED in the FORM of a cone and fitted into a funnel by moistening it with few drops of water (iii) The mixture is poured gently in to the filter cone and collected into another beaker which is called filtrate. (iv) solid RETAINED on the filter paper is called RESIDUE.

Discussion

5.	Sand and saw dust are mixed with water. Name the techniques that can separate sand and saw dust from water.
Answer» SOLUTION :As the DENSITY of sand is more than saw DUST, it settles down and saw dust floats on water. Sand can be separated by SEDIMENTATION and decantation. Saw dust can be separated by filtration.

Discussion

6.	'Sand and clay which are abundantly available in theearth's crust have significant roles in the comfort zone of modern life''. Comment on this statement.
Answer» Solution :Sand is the important component in all types of mortars such as lime mortar andcement mortar.Sand is also the component of cement concrete and reinforced cement concrete (RCC) which contributes to the infrastructure development invarious fields of modern LIFE. Clay palys important role in ceramics,bricksand various building material, sanitary equipment and household ARTICLES. Because of their DESIRED properties they CONTRIBUTE to a significant role in the comfort zone of modern life.

Discussion

7.	Salt used in purification of water is
Answer» potash alum epsom salt green vitriol BLUE vitriol Solution :Potash alum is USED in purification of water as it HELPS in hastening of sedimentation of suspended IMPURITIES.

Discussion

8.	Salt solutions are good conductors of electricity. This is due to the presence of _______ in solution state.
Answer» mobile electrons mobile IONS molecules both 1 and 3 Solution :Salt SOLUTIONS are good conductors of electricity DUE to the FORMATION of mobile ions.

Discussion

9.	Salt is added to pure water to increase its electrical conductivity.
Answer» SOLUTION :Pure water is a BAD conductor of electricity. Salt or alkali is added to water to INCREASE its CONDUCTIVITY.

Discussion

10.	Saline water contains large amounts of dissolved salts.
Answer» SOLUTION :The water which contains large AMOUNTS of dissolved salt is CALLED SALINE water.

Discussion

11.	Rusting of iron is an example of both physical and chemical change.
Answer» SOLUTION :False Rusting of iron is a chemical change in which iron GETS CORRODED in HUMID AIR .

Discussion

12.	Role of nitre in the manufacture of gun powder is ______ .
Answer» to supply OXYGEN to supply nitrogen to decrease the RATE of combustion to absorb TEMPERATURE produced by combustion Solution :Nitre is `KNO_(3)`, which on heating gives `KNO_(2) "and" O_(2)`. The LIBERATED oxygen is the SOURCE for the combustion of carbon and sulphur.

Discussion

13.	Regeneration of anion exchange resin is carried out by passing
Answer» sodium HYDROXIDE SOLUTION sodium chloride solution sodium BICARBONATE solution All the above Solution :Anion exchange RESIN can be regenerated by passing sodium hydroxide solution because it can replenish `OH^(-)` ions.

Discussion

14.	Rate of evaporation of water
Answer» is more in COASTAL area than in non coatal area. is more in non coastal area than in coatal area. is the same in both caostal and non coastal areas. Cannot be predicted. Solution :RATE of evaporation is inversely PROPORTIONAL to humidity. In non-coastal areas humidity is less when COMPARED to coastal areas, and hence rate of evaporation of water is more in a non-coastal area when compared to coastal area.

Discussion

15.	Pyrex or borosil glass is used for making laboratory apparatus whereas crown glass in used in themanufacture of optical instruments. Give reason.
Answer» SOLUTION :PYREX or borosil glass consists of borax which reduces theexpandability of glass and provides heat resistance whereas of red lead in crown glass increases THEDENSITY of glass to a GREAT extent making it useful for optical INSTRUMENTS.

Discussion

16.	Pure nitric acid on longstanding turns to yellow due to the formation of
Answer» `O_(2), NO "and" H_(2)O` `O_(2), NO_(2) "and" H_(2)O` `NO, NO_(2) "and" H_(2)O` `N_(2)O, O_(2) "and" H_(2)O` Solution :Pure nitric acid is highly unstable and hence undergoes decomposition forming `NO_(2), H_(2)O "and" O_(2)*NO_(2)` is a reddish BROWN gas. Dilute solution of `NO_(2)` appears as YELLOW colour. `4HNO_(3) RARR 4NO_(2) + 2H_(2)O + O_(2)`

Discussion

17.	Pure HNO_(3) is colourless, howerver, it gradually becomes yellow on standing due to _______ .
Answer» the decomposition of `HNO_(3)` and formation of NO. the decomposition of `HNO_(3)` and formation of `NO_(2)`. oxidation by atmospheric `O_(2)` and formation NO. oxidation by atmospheric `O_(2)` and formation of `NO_(2)`. Solution :Pure `HNO_(3)` is highlly unstable which undergoes decomposition giving `H_(2)O, O_(2) "and" NO_(2)* NO_(2)` is a reddish brown gas dissolves in `HNO_(3)` and IMPART yellow colour. `4HNO_(3) rarr 2H_(2)O + 4NO_(2) + O_(2)`

Discussion

18.	Property responsible for spreading of fragrance of flower is ________ .
Answer» compressibility of gas/vapour diffusion of gas/vapour expansibility of gas/vapour Both 3 and 2 Solution :Molecules of gas/vapour DIFFUSE EASILY into each other.

Discussion

19.	Property exploited in the usage of perfumes is _______ .
Answer» compressibility of GASES diffusion of gases expansibility of gases Both (3) and (2) Solution :In gases, intermolecular space is more, so they undergi expansion by RELEASING pressure and hance they diffuse into each other forming a homogeneous mixture.

Discussion

20.	Preparation of salt from sea water involves
Answer» EVAPORATION filtration sedimentation and decantation sublimation Solution :Preparation of SALT from sea WATER INVOLVES evaporation in which water undergose evaporation LEAVING behind salt.

Discussion

21.	Predict the valencies of the elements with atomic numbers 7 , 15 , 16 , 18 , 19 and justifyAlso give the formulae of hydrides formed by the above elements if any.
Answer» SOLUTION : Since N andP need three more electrons to ATTAIN octet , their valencies are 3. Similarly , the valencies of other elements with atomic NUMBER 16 , 18 , 19 are 2 , 0 and 1 respectively. Except argon , all other elements forms hydrides. Phosphorus`- PH_(3)`, Potassium- KH Nitrogen`NH_(3)` SULPHUR`- H_(2)S` Argon does not from any COMPOUND

Discussion

22.	Potassium chlorate on strong heating gives potassium chloride and oxygen . Whattype of reaction is this?
Answer» SOLUTION :It is DECOMPOSITION REACTION.

Discussion

23.	Platinum is used as a catalyst.
Answer» Solution :TRUE REASON : Platinumused as a catalyst for most of the REACTIONS that take PLACE in gaseouse state.

Discussion

24.	Plastics are polymers.
Answer» SOLUTION :TRUE REASON : PLASTICS are POLYMERS.

Discussion

25.	Pick out the correct statement (s) among the following.
Answer» An ALLOY is a homogenous mixture of two more METALS. An alloy may contain a NON metal in addition to metals. Alloys possess better PHYSICAL PROPERTIES than the metals. All the above. Solution :An alloy is a homogenous mixture of two or more metals or may contain a non-metal in addition to metals. These alloyspossess better physical properties than the metals.

Discussion

26.	Permanent hardness is removed by Clark's method.
Answer» Solution :CLARK's method is USED for the removal of TEMPORARY HARDNESS.

Discussion

27.	Percentage of water in animals varies from ______ to ______.
Answer» SOLUTION :Percentage of WATER in ANIMALS VARIES from 70 to 90%

Discussion

28.	People used to apply a coating of sodium silicate on eggs for the purpose of preservation. Justify.
Answer» SOLUTION :Sodium or potassium SILICATE is used as a protective covering for EGGS. When egg is dipped in solution of sodium silicate inwater a layer of sodium silicate forms on the surface of egg which is very impervious to water, air and heat.As a result bacterial growth PREVENTED in egg so that it can be preserved for relatively longer periods of time.

Discussion

29.	Ozone present in …………plays a role in protecting the life on surface from harmful UV rays.
Answer» Troposphere stratosphere mesosphere ionosphere Solution :Ozone PRESETN in stratophere PLAYS a vital ROLE in protecting the life on the EARTHS surface form harmful UV rays.

Discussion

30.	Oxygen is ………………… towards litmus.
Answer» SOLUTION :OXYGEN is NEUTRAL TOWARDS LITMUS

Discussion

31.	Oxygen is neutral towards litmus.
Answer» Solution :OXYGEN is neutral towards LITMUS as it is NEITHER ACIDIC nor basic.

Discussion

32.	One molecule of H_(3) PO_(4) is treated with one molecule of NaOH, two molecues of NaOH and three molecules of NaOH separately. Comment on the nature of products formed and write their names.
Answer» SOLUTION :`H_(3)PO_(4) + NaOH rarr underset("Acidic salt")(NaH_(2)PO_(4) + H_(2)O)` `H_(3)PO_(4) + 2NaOH rarr underset("Acidic salt")(Na_(2)HPO_(4) + 2H_(2)O` `H_(3)PO_(4) + 3NaOH rarr underset("NEUTRAL salt")(Na_(3)PO_(4) + 3H_(2)O)` `NaH_(2)PO_(4) rarr` Sodium dihydrogen phosphate `Na_(2)HPO_(4) rarr` DISODIUM hydrogen phosphate `Na_(3)PO_(4) rarr` Sodium phosphate

Discussion

33.	One molecule of an 'ic' acid of a nonmetal having 5 electrons in valence shell reacts with a molecule of base to form a salt 'X'. The base corresponds to the metal with one electron in valence shell. If the salt so formed can react with the same base in 1 : 2 ratio, predict the formula of the salt 'X'.
Answer» `K_(2)SO_(4)` `Na_(2)HPO_(4)` `KH_(2)PO_(4)` `Na_(3)PO_(4)` Solution :The nonmetal with 5 valence electrons is phosphorus and 'ic' acid of phosphorus is phosphoric acid. Metal with one electron in valence shell forms BASE of the formula MOH. Since the SALT can react with two molecules of base, the salt contains two replaceble hydrogens. The formula of salt'X' is `KH_(2)PO_(4)`.

Discussion

34.	On passing electricity through acidulated water, the gaseous products obtained are collected in two separate test tubes A and B. The volume of the gas collected in test tube A is double the volume of gas collected in test tube B. Identify the two gases in test tube A and B.
Answer» Hydrogen and oxygen Oxygen and hydrogen Hydrogen peroxide and oxygen Oxygen and WATER vapour Solution :On passing electricity through acidulated water it decomposes to hydrogebn and oxygen. VOLUME of hydrogen EVOLVED in TEST TUBE A is double the volume of oxygen collected in test tube B.

Discussion

35.	On passing electricity through acidulated water, the gaseous products obtained are collected in two separate test tubes A and B. The volume of the gas collected in test tube A is double the volume of gas collected in test tube B. Identify the two gases in test tubes A and B respectively.
Answer» Hydrogen and OXYGEN Oxygen and hydrogen Hydrogen peroxide and oxygen Oxygen and water vapour Solution :On passing ELECTRICITY through ACIDULATED water it DECOMPOSES to hydrogebn and oxygen. Volume of hydrogen evolved in test tube A is double the volume of oxygen COLLECTED in test tube B.

Discussion

36.	Odd one among the following with respect to the strength of acids is
Answer» PHOSPHORIC acid carbonic acid SULPHURIC acid acetic acid Solution :Sulphuric acid is a STRONG acid, as sulphuric acid ionizes completely in water to FURNISH large concentration of `H^(+)` IONS.

Discussion

37.	O_(2)" and "CO_(2) prepared in the laboratory can be collected by ……….
Answer» downward displacement of WATER and downward displacement of air respectively downward displacement of water and upward displacement of air respectively upward displacement 0f water in both cases downward displacement of water in both cases Solution :`O_(2)` is COLLECTED by downward displacement of water and `CO_(2)` is collected by upward displacement of air. `O_(2)` is insoluble in water whereas `CO_(2)` in SOLUBLE in water.

Discussion

38.	Number of atoms on either side of a chemical equation is balanced by keeping appropriate coefficients and not by changing the subscripts of the element in the formulae . Justify .
Answer» Solution :If subscripts are changed, the molecular FORMULA the is COMPOSITION is changed. Hence the number of atoms on either side of a CHEMICAL equatoin is balanced by keeping appropriate coefficients.

Discussion

39.	Non-metals usually exist in _______ state.
Answer» SOLUTION :GASEOUS A non-metal GENERALLY EXISTS in the gaseous STATE.

Discussion

40.	Non-metals are generally non-malleable and non-ductile.
Answer» SOLUTION :TRUE REASON : Non-metals are GENERALLY nonmalleable and nonductile

Discussion

41.	Noble gases are chemically _________ .
Answer» SOLUTION :INERT NOBLE GASES are CHEMICALLY inert.

Discussion

42.	Nitrogen dilutes the activity of ………. In atmosphere.
Answer» Ar `CO_(2)` `O_(2)` He Solution :NITROGEN DILUTES the ACTIVITY of OXYGEN in the atmosphere.

Discussion

43.	Nitre is the common name of sodium nitrate.
Answer» Solution :NITRE is the COMMON NAME of potassium nitrate.

Discussion

44.	Nitre is the common name of __________.
Answer» SOLUTION :NITRE is the COMMON name of POTASSIUM NITRATE.

Discussion

45.	Naturally occurring diamonds are sometimes foundin different colours. Give reasons.
Answer» Solution :Naturally occurring DIAMONDS are ASSOCIATED with some IMPURITIES. These impurities have CHARACTERISTIC colours and RETAIN these colours in diamonds, hence naturally occurring diamonds are found to be in different colours.

Discussion

46.	Nascent hydrogen is a strong ………… agent. (reducing/oxidizing)
Answer» SOLUTION :NASCENT HYDROGEN is a STRONG REDUCING agant.

Discussion

47.	Name two states of metter which are fluid.
Answer» SOLUTION :LIQUIDS and GASES are FLUIDS.

Discussion

48.	Name two metals which find application in ayurvedic medicine.
Answer» Solution :Gold and silver METALS FIND APPLICATION in AYURVEDIC medicine.

Discussion

49.	Name two metals that can exhibit variable valency .Also give thenames of redicals.
Answer» Solution :COPPER and Iron `{:("Copper :","Cuprous "Cu^(+)),(,"Cupric "Cu^(2+)),("Iron:","Ferrous "FE^(+2)),(,"FERRIC "Fe^(+3)):}`

Discussion

50.	Name two metal carbontes from which carbon dioxide can not be prepared by heating.
Answer» SOLUTION :CARBONDIOXIDE cannot be PREPARED by heating SODIUM carbonate and POTASSIUM carbonate.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Small water droplets associated with dust particles to form larger aggregates called ______

SI unit of atmospheric pressure is

Sand and saw dust are mixed with water. Name the techniques that can separate sand and saw dust from water.

'Sand and clay which are abundantly available in theearth's crust have significant roles in the comfort zone of modern life''. Comment on this statement.

Salt used in purification of water is

Salt solutions are good conductors of electricity. This is due to the presence of _______ in solution state.

Salt is added to pure water to increase its electrical conductivity.

Saline water contains large amounts of dissolved salts.

Rusting of iron is an example of both physical and chemical change.

Role of nitre in the manufacture of gun powder is ______ .

Regeneration of anion exchange resin is carried out by passing

Rate of evaporation of water

Pyrex or borosil glass is used for making laboratory apparatus whereas crown glass in used in themanufacture of optical instruments. Give reason.

Pure nitric acid on longstanding turns to yellow due to the formation of

Pure HNO_(3) is colourless, howerver, it gradually becomes yellow on standing due to _______ .

Property responsible for spreading of fragrance of flower is ________ .

Property exploited in the usage of perfumes is _______ .

Preparation of salt from sea water involves

Predict the valencies of the elements with atomic numbers 7 , 15 , 16 , 18 , 19 and justifyAlso give the formulae of hydrides formed by the above elements if any.

Potassium chlorate on strong heating gives potassium chloride and oxygen . Whattype of reaction is this?

Platinum is used as a catalyst.

Plastics are polymers.

Pick out the correct statement (s) among the following.

Permanent hardness is removed by Clark's method.

Percentage of water in animals varies from ______ to ______.

People used to apply a coating of sodium silicate on eggs for the purpose of preservation. Justify.

Ozone present in …………plays a role in protecting the life on surface from harmful UV rays.

Oxygen is ………………… towards litmus.

Oxygen is neutral towards litmus.

One molecule of H_(3) PO_(4) is treated with one molecule of NaOH, two molecues of NaOH and three molecules of NaOH separately. Comment on the nature of products formed and write their names.

On passing electricity through acidulated water, the gaseous products obtained are collected in two separate test tubes A and B. The volume of the gas collected in test tube A is double the volume of gas collected in test tube B. Identify the two gases in test tube A and B.

On passing electricity through acidulated water, the gaseous products obtained are collected in two separate test tubes A and B. The volume of the gas collected in test tube A is double the volume of gas collected in test tube B. Identify the two gases in test tubes A and B respectively.

Odd one among the following with respect to the strength of acids is

O_(2)" and "CO_(2) prepared in the laboratory can be collected by ……….

Number of atoms on either side of a chemical equation is balanced by keeping appropriate coefficients and not by changing the subscripts of the element in the formulae . Justify .

Non-metals usually exist in _______ state.

Non-metals are generally non-malleable and non-ductile.

Noble gases are chemically _________ .

Nitrogen dilutes the activity of ………. In atmosphere.

Nitre is the common name of sodium nitrate.

Nitre is the common name of __________.

Naturally occurring diamonds are sometimes foundin different colours. Give reasons.

Nascent hydrogen is a strong ………… agent. (reducing/oxidizing)

Name two states of metter which are fluid.

Name two metals which find application in ayurvedic medicine.

Name two metals that can exhibit variable valency .Also give thenames of redicals.

Name two metal carbontes from which carbon dioxide can not be prepared by heating.

Percentage of water in animals varies from to .