908 + Interview Questions in Chemistry in Class 7

1.	Two thermometers A and B are dipped in water and alcohol respectively taken in two containers of similar diamensions at room temperature. Compare the temperatures shown by these two thermometers giving appropriate reasons.
Answer» Solution :The rate of evaporation depends upon the nature of the liquid. In case of ALCOHOL, the SURFACE molecules possess high kinetic energy as a RESULT they easily escape into atmosphere that is the of evaporation is more. As evaporation causes cooling, decrease in temperature in case of alcohol is more. DUE to this reason, a decrease in the level of mercury is OBSERVED in the case observed in the case of container B having alcohol but not in the case of A having water.

Discussion

2.	What is the volumetric composition of water?
Answer» SOLUTION :The VOLUMETRIC COMPOSITION of hydrogen and oxygen in water is in the RATIO of 2 : 1.

Discussion

3.	Which of the following processes is not involved in the purification of drinking water?
Answer» SEDIMENTATION Filtration Chlorination Distillation Solution :Distillation PROCESS is not involved in the PURIFICATION of DRINKING water.

Discussion

4.	What is a chemical displacement reaction ? Mention the condition required for it.
Answer» Solution :The chemical reaction in which the more REACTIVE element displaces the LESS reactive elementfrom its compound is CALLED chemical DISPLACEMENT reaction. `X+YZtoXZ+Y` X is more reactive element than y. `Y+XZto`Noreaction Y cannot displace X from its compound SINCE it is less reactive than X.

Discussion

5.	X and Y arenon mtalsin whichM shell is valence shell . Y is precedent to X . X shows uninegative valence . Identify the formulae of the compounds formed when X and Y react with divalent metal M.
Answer» `MX_(2),MY` `MX,MY_(2)` `M_(3)X_(2),M_(2)Y_(3)` `M_(2)X_(3),M_(3)Y_(2)` Solution :Electronic configuration ofX is 2 , 8 , 7 Electronic configuration of Yis 2 , 8 , 6 `:.` VALENCIES of X and Y are 1 and 2 respectively. `M^(+2)X^(-)""M^(+2)Y^(-2)` `MX_(2) "" MY`

Discussion

6.	Two test tubes X and Y are filled with water and mercury, respectively. After these two liquids were poured, water drops on the inner walls of X were observed but no mercury drops in Y were seen. Give reasons.
Answer» SOLUTION :In between WATER molecules and glass molecules, adhesive forces continually act which are predominant over cohesive forces and hence water droplets are observed on the INNER walls of the glass TUBE X. In case of mercury cohesive forces are more than adhesive forces and hence mercury, droplets are not observed on the inner walls of 'Y'.

Discussion

7.	Write the electronic configurations of the followingelements.(a) magnesium(b) Silicon(c )Sulphur(d) Argon
Answer» Solution :(a)MAGNESIUM`(Z=12)to(2,8,2)` (B)Silicon `(Z=5)to(2,8,4)` (C ) BORON`(Z=5)to(2,3)` (d) Argon `(Z=18)to(2,8,8)`

Discussion

8.	What is permutit? Give its formula?
Answer» Solution :Hydrated SODIUM aluminium silicate is called permutiet. Formula of permutit is `Na_(2) Al_(2)Si_(2)O_(8) XX H_(2)O`

Discussion

9.	Which among the following is a weak acid?
Answer» SULPHURIC ACID Hydrochloric acid NITRIC acid CARBONIC acid Solution :Carbonic acid is a WEAK acid.

Discussion

10.	When the temperature of water rises from 0^(@)C to 10^(@)C, the density of water
Answer» decreases gradually. decreases up to `4^(@)C` and then INCREASES. increases up to `4^(@)C` and then decreases. increases gradually. Solution :DENSITY of water is maximum at `4^(@)C` du to anomalous EXPANSION of water. Hence, when the temperature of water is raised from `0^(@)C` to `10^(@)C`, the density increases up to `4^(@)C`, then decreases gradually.

Discussion

11.	Which of the following compounds/alloys of silicon in used in grinding wheel and which property of that substance is exploited ?
Answer» Silicon carbide because it is the HARDEST substance. Ferrosilicon because it is resistant to friction. Sodium silicate because it becomes impervious when heated strongly. Silicon dioxide because it is resistant to chemicals. Solution :Silicon carbide is used in GRINDING WHEELS because it is the hardest substance.

Discussion

12.	Which of the following materials can be used for plastering ?
Answer» Cement MORTAR Concrete RCC Anyone of THEABOVE SOLUTION :Cementmortar is USED for plastering.

Discussion

13.	Which among the following is a heterogeneous mixture ?
Answer» SODA water Air Milk Sugar water Solution :Milk is a heterogeneous MIXTURE in which FAT PARTICLES are present in water.

Discussion

14.	Three elements form their respective oxides A, B and C. A and C are gases and 'B' is a solid which on dissolution in water turns red litmus to blue. In presence of moisture, 'A' turns blue litmus red and 'C' is neutral to litmus. Then, A,B and C may be respectively
Answer» `SO_(3), MgO, NO` `SO_(2), CAO, CO_(2)` `CO, Na_(2)O, SO_(3)` `SO_(2), Ca(OH)_(2), NO_(2)` SOLUTION :`SO_(3)` in presence of moisture TURNS blue red. 'NO' is neutral oxide and does not respond to litmus test. MgO is basic and turns red litmus blue.

Discussion

15.	Which of the following substances does not form a curdy precipitate when it is added to hard water?
Answer» Potassium salt of FATTY acid. Sodium salt of fatty acid. sodium lauryl sulphate. None of the above. Solution :Sodium lauryl sulphate does not FORM a CURDY PRECIPITATE in HARD water.

Discussion

16.	Thermal exparision of solids is the least among the three states of matter due to
Answer» high kinetic ENERGY of molecules of solids. close packing of molecules solids. the vibratory motion and rotatory motion of molecules of solids. the large intermolecular SPACE present in solids. SOLUTION :In solid the molecules are closely packed due to strong FORCES of attraction and hance thermal expansion of solid is least among the three state states of matter.

Discussion

17.	What is valency ? Write short note on different types of valencies of cations with examples.
Answer» Solution :VALENCY : The number of electrons gained or lost by an atom of an element for attaining stable octet or duplet connfiguration is called valency. When an atom loses one or more electrons , the number of PROTONS init becomes more than the numberof electrons and hence the ions formed are left with POSITIVE charge . this is called positive valency. When an atom attains stability by GAINING one or more electrons, the number of electrons in it becomes more than the number of protins and hence the ion formed becomes negatively charged. this is called negative valency. The charge on the ion is corresponding to the number of electrons lost or gained . they may be monovalent , bivalent , trivalent and tetravalent which correspond to VALENCIES , 1, 2, 3, 4 respectively.

Discussion

18.	What is the composition of water gas and how is it formed ?
Answer» Solution :Water gas is the MIXTURE of equal volumes of carbon monoxie and hydrogen. Water gas can be prepared by PASSING steam over RED HOT coke. `underset("steam")(C+H_(2)O)tounderset("Water gas")(CO+H_(2))`

Discussion

19.	The symbol of cobalt is _______.
Answer» SOLUTION :CO Thesymbol of COBALT is Co.

Discussion

20.	What are the values of latent heat of fusion of ice and latent heat of vapourisation for water?
Answer» Solution :The value of latent HEAT of FUSION of ice and latent heat of vapourisation of WATER are 80 cal/g and 540 cal/g RESPECTIVELY.

Discussion

21.	Whatis the difference between symbol and formula ?
Answer» SOLUTION :Symbols can be defined as the shorthanf notations which represent a SINGLE ATOMS of elements Formula can be defined as the short HAND notation which represent a molecule of an ELEMENT or compound.

Discussion

22.	Which of the following process is not associated with formation of metal nitrates in soil ?
Answer» Acid rain Nitrogen FIXATION by leguminous plants Lightning followed precipitation Formation of AURORAS Solution :Acid rain, nitrogen fixation and lighterning processes are associated with the formaion of metal `HNO_(3)` when reacts reacts with salts present in the soil, gets converted to CORRESPONDING metal nitrates. Formation of auroras involves collision of ELECTRONS with molecules of `N_(2)" ana "O_(2)` and emission of beautiful RADIATIONS. It does not result in formation of nitrates.

Discussion

23.	Write the step in balancing a chemical equation with an example.
Answer» SOLUTION :Example :`Mg+O_(2)to MgO`is an UNBALANCED chemical equation . THISIS called skeletal equation .A systematic procedure should be following for balancing the chemical equation. StepI The number of times an element occurs on both sides is counted . the element which appears the least number of times should be balanced first. StepII Among THEELEMENTS with same frequency of occurrences , the metallic element is balanced first followed by NONMETALLIC element. Step IIIHydrogen and oxygen is balanced at the end. Examples :R""P `Mg+O_(2)toMgO` `1-Mg-1` `2-O-1` `Mg+O_(2)to2MgO` `1-Mg-2` `2-O-2` `2Mg+O_(2)to2MgO`

Discussion

24.	What type of metals are found in free state ?
Answer» SOLUTION :Noble metals like GOLD, platinum, SILVER are found in free state

Discussion

25.	What is the role of water vapour in the formation of fog ?
Answer» Solution :The presence of water vapour in atmosphere INFLUENCES the flimatic conditions. Water vapour presetn in atmosphere gets condensed on DUST particles during NIGHT time (winter nights) because of low temperaute.Depending up on the temperature, the water vapour produces snow, for, mist, hails and other phenomenon's. When water vapour condenses on dust particles and REMAINS supended in atmosphere, itis called fog.

Discussion

26.	When the temperature of water rises from 0^(@)C to 10^(@)C,the density of water
Answer» decreases gradually. decreases up to `4^(@)C` and then INCREASES. increases up to `4^(@)C` and then decreases. increases gradually. SOLUTION :Density of water is maximum at `4^(@)C` due to anomalous EXPANSION of water. Hence, when the temperature of water is RAISED from `0^(@)C` to `10^(@)C`, the density increases upto `4^(@)C`, then decreases gradually.

Discussion

27.	Which of the following is a biodegradable substance?
Answer» Detergent Pesticides Polythene Waste OBTAINED from biogas PLANT Solution :The waste obtained from biogas plant can be USED as manure as it is an ORGANIC MATTER.

Discussion

28.	What is blue vitriol? Write its method of preparation and its uses?
Answer» Solution :BLUE vitriol is hydratedcoppersulphateprepared by dissolved cupric sulphide or cupric oxide or cupric carbonate in DILUTE in dilute sulphuric ACID. It finds application as an insecticide. Solution of copper SULPHATE is sprayed overcitrus trees and graps vines to kill theinsects.

Discussion

29.	Which of the following salts is responsible for temporary and permanent hardness of water respectively?
Answer» `Mg(HCO_(3))_(2)and Na_(2)SO_(4)` `Ca(HCO_(3))_(2) and MgCl_(2)` `MgSO_(4)and Mg(HCO_(3))_(2)` `CaCl_(2) and CaSO_(4)` Solution :Bicarbonates of calcium and magnesium and chlorides and sulphates of calcium and magnesium are responsible for TEMPORARY and permanent hardness respectively.

Discussion

30.	The reaction of which of the following metal steam is reversible ?
Answer» Calcium Aluminium IRON Lead Solution :The REACTION of iron with STEAM REVERSIBLE REATION.

Discussion

31.	The reactionAgNO_(3)+NaCl toAgCl+ NaNO_(3) is a ________ reaction.
Answer» chemical DISPLACEMENT chemical combination DOUBLE displacement decomposition Solution :`AgNO_(3)+NaCl+NaNO_(3)` is a double displacement REACTION.

Discussion

32.	The ratio of number of electrons present I four shells of an element is1 : 4 : 4 : 1, fourth shellis the valence shell . Thenmassof total positive charge present in the atom is ____________ times to that of mass of electron
Answer» 36 , 704 27 , 555 18 , 370 55, 110 Solution :Theelectronic configuration of the ELEMENT is `{:(K,L,M,N),(2,8,8,2):}` THEREFORE the atomic number is 20 . We know that mass of PROTON is 1837 TIMES that of electron, therefore total positive charge present is `20x1837 =36740`,

Discussion

33.	The ratio of difference in the numberof electrons between K and M shells is3 :2for X and Y elements respectively . 'X' possesses stable electronic configuration and M is the valence shell for both X and Y. Give the electronic configurationsof X and y.
Answer» 2 , 8 , 5 and2 , 8 , 4 2 , 8 , 8 and 2 ,8 , 6 2 , 8 , 8 and2 , 6 , 6 2 , 8 , 6 and 2 , 8 , 4 Solution :`{:(X,:,Y),(3,:,2),(2_(,)8_(,)8,,2_(,)8_(,)x),((8-2)/(x+2)=(3)/(2),,,X=6):}` `:.Xto2,8,8andYto2,8,6`

Discussion

34.	The ratio of difference in the number of electrons between K and M shells is3 :2 for X and Y elements respectively . 'X' possesses stable electronic configuration and M is the valence shell for bothX and Y. The electronic configurations of X and Y are respectively.
Answer» 2 , 8 , 5 AND2 , 8 , 4 2 , 8 , 8 and 2 ,8 , 6 2 , 8 , 8and 2 , 6 , 6 2 , 8 , 6 and 2 , 8 , 4 Solution :`{:(X,:,Y),(2_(,)8_(,)8,,2_(,)8_(,)x),((8-2)/(x-2)=(3)/(2),,rArrx=6):}` `:.Xto2,8,8and Yto2,8,6`

Discussion

35.	The process of separation of components of muddy water is
Answer» decantation sublimation MAGNETIC separation None of these Solution :The process is decantation as mud being HEAVIER than water SETTLES down at the bottom DUE to gravity and SEPARATES from water

Discussion

36.	The process of coating zinc on iron surface is called __________
Answer» SOLUTION :Gold AMALGAM The ALLOY formed gold and MERCURY is called gold amalgam.

Discussion

37.	Theprocess of coating zinc on iron surface is called _________
Answer» SOLUTION :GALVANIZATION Theprocess of COATING ZINC on iron surface is called galvanization.

Discussion

38.	The pressure cooker reduces the cooking time because of
Answer» INCREASE in the boiling point of water high specific heat of water decrease in the boiling point of water high latent heat of vapourization Solution :Cooking in a pressure cooker TAKES less time because in pressure cooker as pressure increases boiling point increases and food is COOKED softer in less time.

Discussion

39.	The percentage of noble gases present in air is more than that of CO_(2).
Answer» Solution :The percentage of noble GASES is 0.94% and that of `CO_(2)` is 0.03% in ATMOSHPHERE.

Discussion

40.	The pair of ions which does not cause hardness of water is
Answer» sulphate, chloride bicarbonate, chloride bicarbonate, sulphate NITRATE, phosphate Solution :Nitrate and phosphate IONS do not CAUSE HARDNESS of water

Discussion

41.	The Ozone present in the troposphere is a major pollutant. However, ozone formation in aquua purifiers, makes drinking water pure and safe. Explain.
Answer» SOLUTION :Aqua PURIFIERS consist of energy source which source which radiates UV rays. Oxygen is CONVERTED to ozone in presence of ULTRA violet rays. Theozone decomposis into oxygen and nascent oxygen in presence of UV rays. The nascent oxygen has ability to kill the harmful micro organisms present in water and HENCE water gets purified. `3O_(2)to2O_(3)` `O_(3)toO_(2)+[O]`

Discussion

42.	The number of valence electrons in the valece shells , 1 , 2 , 3of theX , Y , Z elements are 2 , 8 , 6 respectively . Identify the element which doesn ' t exist monoatomic state.
Answer» X Z Y XandY Solution :`{:(" Element",X,Y,Z),("VALENCE shell",underset((1))(K),underset((2))(L),underset((3))(M)):}` No . Of valence `{:("Electrons",2,8,6),("Element","He","Ne","S"):}` SULPHUR doesn ' t exist in monoatomicstate due to its greater chemical REACTIVELY.

Discussion

43.	The numberof positively charged particles in the elements A, B, C are 10, 18, 8respectively . Identify the element which is chemically reactive?
Answer» A B C Both A and B Solution :`{:("Element",'Z',"Electronic Configuration"),("A",10,2_(,)8),("B",18,2_(,)8_(,)8),("C",8,2_(,)6):}` HENCE , 'C' is chemically REACTIVE . A and B are chemically becauseof stable OCTET configuration.

Discussion

44.	The number of neutrons are equal to the numberof protons present in the nucleus of two elements and their respective dinegative ions possess 8 electrons in L and M shells respectively . Then the ratio of mass numbers of the two elements is
Answer» `1 :2` ` 3:3` `3:4` `2:5` Solution :The ELECTRONIC CONFIGURATION of the dinegative ion with 8 ELECTRONS in VALENCE shell (L shell) is `X^(2)to2 , 8` `Xto2 , 6 (Z)` mass number is 16, `Y^(-2)to2 , 8 , 8` `YTO 2 , 8 , 6 (Z)` Mass number is 32 (A) for Y. Ratio ofmass number`16: 32, "" 1 : 2`

Discussion

45.	The number of electrons present in K shells of hydrogen and helium are
Answer» 2 and 1 respectively 2 in both the elements 1 and 2 respectively 1 in both the elements Solution :`H(Z=1)` electronic CONFIGURATION =1, He `(Z=2) electronic configuration =2

Discussion

46.	The number of electrons in second shellof a metal with three valence electrons in the third shell is eight.
Answer» SOLUTION :True The electrons enter III shell after II shell gets COMPLETELY filled by eight electrons.

Discussion

47.	The number of atoms of a molecule or compound are balance on either side of achemical equation by keeping apprpriate_________.
Answer» Solution :COEFFICIENTS The number of atoms ONEITHER side of the chemical eqution are balanced by KEEPING appropriate coefficients.

Discussion

48.	The nucleus consists of
Answer» PROTON and electrons electrons and neutron protons and NEUTRONS All the above Solution :The protons and neutrons are present in nucleus.

Discussion

49.	The name ofCrO_(4)^(-2) radical is dichromate ion.
Answer» SOLUTION :False `Cr_(2)O_(7)^(2-)` CALLED dechromate ion.

Discussion

50.	The most convenient way of separating saw dust from water is
Answer» distillation evaporation FILTRATION sedimentation and decantation Solution :As saw dust FLOATS on WATER, it can separated from water by filtration easily.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Two thermometers A and B are dipped in water and alcohol respectively taken in two containers of similar diamensions at room temperature. Compare the temperatures shown by these two thermometers giving appropriate reasons.

What is the volumetric composition of water?

Which of the following processes is not involved in the purification of drinking water?

What is a chemical displacement reaction ? Mention the condition required for it.

X and Y arenon mtalsin whichM shell is valence shell . Y is precedent to X . X shows uninegative valence . Identify the formulae of the compounds formed when X and Y react with divalent metal M.

Two test tubes X and Y are filled with water and mercury, respectively. After these two liquids were poured, water drops on the inner walls of X were observed but no mercury drops in Y were seen. Give reasons.

Write the electronic configurations of the followingelements.(a) magnesium(b) Silicon(c )Sulphur(d) Argon

What is permutit? Give its formula?

Which among the following is a weak acid?

When the temperature of water rises from 0^(@)C to 10^(@)C, the density of water

Which of the following compounds/alloys of silicon in used in grinding wheel and which property of that substance is exploited ?

Which of the following materials can be used for plastering ?

Which among the following is a heterogeneous mixture ?

Three elements form their respective oxides A, B and C. A and C are gases and 'B' is a solid which on dissolution in water turns red litmus to blue. In presence of moisture, 'A' turns blue litmus red and 'C' is neutral to litmus. Then, A,B and C may be respectively

Which of the following substances does not form a curdy precipitate when it is added to hard water?

Thermal exparision of solids is the least among the three states of matter due to

What is valency ? Write short note on different types of valencies of cations with examples.

What is the composition of water gas and how is it formed ?

The symbol of cobalt is _______.

What are the values of latent heat of fusion of ice and latent heat of vapourisation for water?

Whatis the difference between symbol and formula ?

Which of the following process is not associated with formation of metal nitrates in soil ?

Write the step in balancing a chemical equation with an example.

What type of metals are found in free state ?

What is the role of water vapour in the formation of fog ?

When the temperature of water rises from 0^(@)C to 10^(@)C,the density of water

Which of the following is a biodegradable substance?

What is blue vitriol? Write its method of preparation and its uses?

Which of the following salts is responsible for temporary and permanent hardness of water respectively?

The reaction of which of the following metal steam is reversible ?

The reactionAgNO_(3)+NaCl toAgCl+ NaNO_(3) is a ________ reaction.

The ratio of number of electrons present I four shells of an element is1 : 4 : 4 : 1, fourth shellis the valence shell . Thenmassof total positive charge present in the atom is ____________ times to that of mass of electron

The ratio of difference in the numberof electrons between K and M shells is3 :2for X and Y elements respectively . 'X' possesses stable electronic configuration and M is the valence shell for both X and Y. Give the electronic configurationsof X and y.

The ratio of difference in the number of electrons between K and M shells is3 :2 for X and Y elements respectively . 'X' possesses stable electronic configuration and M is the valence shell for bothX and Y. The electronic configurations of X and Y are respectively.

The process of separation of components of muddy water is

The process of coating zinc on iron surface is called __________

Theprocess of coating zinc on iron surface is called _________

The pressure cooker reduces the cooking time because of

The percentage of noble gases present in air is more than that of CO_(2).

The pair of ions which does not cause hardness of water is

The Ozone present in the troposphere is a major pollutant. However, ozone formation in aquua purifiers, makes drinking water pure and safe. Explain.

The number of valence electrons in the valece shells , 1 , 2 , 3of theX , Y , Z elements are 2 , 8 , 6 respectively . Identify the element which doesn ' t exist monoatomic state.

The numberof positively charged particles in the elements A, B, C are 10, 18, 8respectively . Identify the element which is chemically reactive?

The number of neutrons are equal to the numberof protons present in the nucleus of two elements and their respective dinegative ions possess 8 electrons in L and M shells respectively . Then the ratio of mass numbers of the two elements is

The number of electrons present in K shells of hydrogen and helium are

The number of electrons in second shellof a metal with three valence electrons in the third shell is eight.

The number of atoms of a molecule or compound are balance on either side of achemical equation by keeping apprpriate_________.

The nucleus consists of

The name ofCrO_(4)^(-2) radical is dichromate ion.

The most convenient way of separating saw dust from water is