908 + Interview Questions in Chemistry in Class 7

1.	Calculate the number of neutrons in the following.(a)._(15)X^(31)(b)._(92)"U"^(235)(c )._(19)"K"^(39)
Answer» Solution :(a) Neutrous =31 -15 =16 (b)NEUTROUNS = 235 -92 =143 (C )Neutrons =39 -19 = 20

Discussion

2.	Calculate the amount of heat energy required to increase the temperature of 10 g of water through 12^(@)C.
Answer» Solution :Specific HEAT capacity of water is 1 cal `g^(-1) .^(@)C^(-1)`. 1 cal heat is REQUIRED to increase the temperature of 1 g of water by `1^(@)C`. `THEREFORE` To increase the temperature of 10 g water by `12^(@)C`, 120 calories heat is required.

Discussion

3.	Calcium hydroxide on heating gives a solid product 'X' and on treatment with hydrochloric acid gives another solid product Y. What do you observe whe X and Y are exposed to atmosphere? Explain.
Answer» SOLUTION :`CA(OH)_(2) rarr underset(("X"))(CaO + H_(2)O)` `Ca(OH)_(2) + HC1 rarr underset(("Y"))(CaC1_(2)) + H_(2)O` CaO is hygroscopic in nature absorbs moisture and remains in solid state. `CaC1_(2)` is deliquescent in nature, absorbs moisture and is converted into solution state.

Discussion

4.	Calcium hydroxide is added to soils before applying fertilisers. Justify the purpose.
Answer» Solution :Generally SOILS are slightly acidic in nature. As calcium hydroxide is basic in nature it NEUTRALIZES the acidityof soils. Calcium hydroxide is prepared form NATURALLY occurring LIMESTONE.

Discussion

5.	Calassify the chemical reactions into varous types depending on the way the products are formed by giving suitable examples.
Answer» Solution : (i)Chemical combination : Thereaction in which two substances , that is , ELEMENTS , compounds or both combine to form a new compound is called chemicalcombination. Representation :`X+YtoXY` `{:("Type","Example"),("Element - element (synthesis)",H_(2)+Cl_(2)to2HCl),("Element - compound",2SO_(2)+O_(2)to2SO_(3)),("Compound - compound",CaO+H_(2)OtoCa(OH)_(2)):}` (ii) Chemical decomposition :The reaction in which a compound undergoes decomposition to form more than one substance in the PRESENCE of heat or light or electricity is called chemical decomposition. Representation :`ABtoA+B` `{:("Type","Example"),("Thermal decomposition (In presence of heat)",2Pb(NO_(3))_(2)to2PbO+4NO_(2)+O_(2)),("Photolytic decomposition (In presence of light)",2HOCl to2HCl+O_(2)),("Electrolytic decomposition (By passing electricity)",2H_(2)Oto2H_(2)+O_(2)):}` (iii)Chemical displacement :When few pieces of zinc are dipped ingreen coloured ferrous SULPHATE solution , the COLOUR disappears after some time and ironis found to be deposited .Thisphennomenon takes place because zinc is more active metal than iron and hence it takes away the other constituent that is iron from ferrous sulphate and iron gets separated. Whereas , when copper is added to the ferrous sulphate solution , no change is observed . from this observation it can be concluded that copper is less active metal than iron. The chemical reaction in which the more REACTIVE element displaces the less reactive element from its compound is called chemical displacement reaction. Representation : `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. Example :`Zn+FeSO_(4)toZnSO_(4)+Fe` `Cu+FeSO_(4)to` no reaction (iv)Chemical double decomposition / double displacement : The chemical reaction in which the two reactant (compounds) exchange their respective radicals and two other new compounds are formed is called double displacement reaction. Representation : `AB+XYtoAY+XB` Where B and Ycorrespond to the negative radicals which are exchanged to give AY and XB. Example :`2KNO_(3)+FeSO_(4)toK_(2)SO_(4)+Fe(NO_(3))_(2)` In the above reactive `K^(+)` (potassium ion) combines with `SO^(4-)` (sulphate ion) and `Fe^(+2)` (ferrous ion) combines with `NO^(3-)` (nitrate ion) to form two new compounds , `K_(2)SO_(4) and Fe(NO_(3))_(2)` . During certain double displacement reactions , a solid substance is found to be deposited . The solid deposition is called precipitate and this of reaction is called precipitation reaction. Example :`NaCl+AgNO_(3)toNaNO_(3)+AgCl` in theabove reaction , during the exchange of radicals , silver chloride is formed which is insoluble in water . therefore it remains as a solid at the bottom of the container as precipitate.

Discussion

6.	CaC1_(2) is an example of
Answer» normal salt ACIDIC salt basic salt complex salt Solution :`CaC1_(2)` in an EXAMPLE of normal salt as it is formed by complete neutralisation of ACID and base.

Discussion

7.	Both the formation of mist and clouds involve the condensation of water vapour. In which aspect do they differ from each other ?
Answer» The process of colud formation takes place in summer WHEREAS the process of formation of mist takesplace in winter. The cloud formation takes place in lower layers while mist formation takes place in the upper layers of the troposphere. Clouds are suspended in the atmosphere while mist settles downon leaves, walls etc.., on EARTH's surfaces. The water DROPLETS of cloud have a MUCH TEMPERATURE than that of water droplets of mist. Solution :Formation of mist takes place in lower layers while layers while cloud formation takes place in the upper layers of the troposphere. The process of cloud formation takes place through out the year while the formation of mist takes place only tat certain times at perticular temperatures.

Discussion

8.	Both protons and neutrons possess thesame magnitude of charge but opposite signs.
Answer» SOLUTION :False Neutrons carryno CHARGE i.e., they are NEUTRAL , but all protons are POSITIVELY charged.

Discussion

9.	Both galvanizing and tinning are adopted for preventing of iron but only tinned iron containers are used to preserve food material. Justify.
Answer» Solution :In the process of GALVANIZING. Zinc is coated on the iron, the zinc can react with react with ACIDS present in food MATERIAL as a result food items cannot be concumed. Where as tin cannot react react with acids present in food items hence TINNED iron SHEETS are extensively used for making boxes to store edible substances.

Discussion

10.	Boiling point is the temperature at which _______ is converted to ________ at one atmospheric pressure.
Answer» Solution :LIQUID, gas BOILING POINT is the TEMPERATURE at which a liquid is CONVERTED to gas at one atmospheric presssure.

Discussion

11.	Blue vitriol is used as a fungicide for grape plants.
Answer» Solution :TRUE REASON : Blue vitriol is as fungicide for fruit tree in theform of BORDEAUX MIXTURE.

Discussion

12.	Blue coloured solid anhydrous cobalt chloride is exposed to atmosphere and forms pink coloured solid. From this, we can infer that cobalt chloride is
Answer» HYGROSCOPIC deliquescent efflorescent None of these Solution :Cobalt chloride is a hygroscopic substance and HENCE absorbs MOISTURE and forms pink coloured hydrated cobalt chloride without UNDERGOING any change in its STATE.

Discussion

13.	Between H_(2)SO_(4) "and" H_(3)PO_(4), which solution possesses greater number of H^(+) ions in the given volume assuming that the number of molecules of both acids are equal? Give reasons.
Answer» Solution :As `H_(2)SO_(4)` is strong acid it PRODUCES greater NUMBER of `H^(+)` ions that is complete ionization. `H_(2)SO_(4) rarr 2H^(+) + SO_(4)^(-2)` As `H_(3)PO_(4)` is weak acid it produces LESS number of `H^(+)` ions that is complete ionization. `H_(3)PO_(4) rarr 3H^(+) + PO_(4)^(-3)`

Discussion

14.	Balance the following chemical equations.(i)NH_(3)+Br_(2)toN_(2)+NH_(4)Br(ii)FeS_(2)+O_(2)toFe_(2)O_(3)toSO_(2)
Answer» SOLUTION :(i)`NH_(3)+O_(2)toNO+H_(2)O` `4NH_(3)+5O_(2)to4NO+6H_(2)O` (ii)`FeS_(2)+O_(2)toFe_(2)O_(3)+SO_(2)` `4FeS_(2)+11O_(2)to2Fe_(2)O_(3)+8SO_(2)`

Discussion

15.	Balackening of silverware is a ____________ change.
Answer» SOLUTION :CHMICAL CHANGE. Blackening of SILVERWARE is a CHEMICAL change.

Discussion

16.	Baking soda (NaHCO_(3)) is a compound because
Answer» the CONSTITUENTS retain their properties. the constituents van be SEPARATED by PHYSICAL methods. the constituents are combined CHEMICALLY. it is HETEROGENEOUS in nature. Solution :In banking soda `(NaHCO_(3))`, the constitutions are combined chemically in fixed weight ratio and hance it is compound.

Discussion

17.	Bakelite is an example of ________ plastic.
Answer» SOLUTION :THERMOSETTING BAKELIT is an EXAMPLE of thermosetting PLASTIC.

Discussion

18.	Auroras appear in the layer of atmosphere which is known as …………
Answer» SOLUTION :theremosphere AURORAS APPEAR in the layer of the atmosphere which is KNOW as themosphere.

Discussion

19.	Atomicity of ozone is _________ .
Answer» SOLUTION :THREE OZONE is a TRIATOMIC MOLECULE.

Discussion

20.	Atomic number of a metal having 12 neutrons and mass number 23 is __________ .
Answer» Solution :11 Atomic NUMBER= MASS number = number of neutronsAtomic number = 23 -12 =11

Discussion

21.	Assme that temperature is recorded in the termosphere with the help of a thermometer. You will be amazed to find that the temperature recorded in will be extremely low. This is because
Answer» of the complete absorption of high energetic radiations by MOLECULES. of the absence of ATMOSPHERE. of the PRESENCE of very few molecules of ions. it is very high altitudes. Solution :Due to a very thin atmosphere in the termosphere, only a few molecules PRESETN here absorb high energetic rediations and hence the temperature of molecules of inons formed is GREAT but the ambient temperature is very low.

Discussion

22.	Assertion (A): When carbon dioxide gas is passed through lime water, lime water is turned milky. Reason (R): Calcium carbonate is soluble in water.
Answer» Both (A) and ( R) are true and ( R) is the correct explanation for (A). Both (A) and (R ) are true but ( R) is not the correct explanation for (A). (A) is correct but ( R) is false. (A) is false but (R ) is trues. Solution :When CARBON dioxide GAS is passed through limewater is gives white precipitate due to formation of CALCIUM CARBONATE which is insoluble in water.

Discussion

23.	Assertion (A) : Washing soda (Na_(2)CO_(3)) is a compounds. Reason (R ) : Sodium retains its property in washing soda.
Answer» Both A and R are true and R is the correct explanation for A. Both A and R are true but R is not the correct explanation for A. A is true and R FALSE. A is false and R is true. Solution :Washing soda is a compound since the constituents combine chemically. In a compound, constituents do not RETAIN their properties. Since sodium is the constituent of washing soda `(Na_(2)CO_(3))` it does not retain its properties

Discussion

24.	Assertion (A) : Tin is used in the manufacture of fusible alloys. Reason (R) : Tin is a good conductor of electricity.
Answer» Both (A) and (R)are true and (R) is the correct reason of (A). Both (A) and (R) are true but (R) is not the correct EXPLANATION of (A). (A) is true but (R) is FALSE. (A) is false but (R) is true. Solution :Tin is used inthe MANUFACTURE of fusible alloy as it has very LOW MELTING point.

Discussion

25.	Assertion (A) : The total mass of the protons of a born atom is 6185 times the total mass of electrons.Reason (R ) : Mass of one proton is times the mass of electron.
Answer» Both A and R are true and R is the correct explanation For A. Both A and R are true but R is not the correct explanationfor A. A is true and R is false. A is false and R is true. Solution :Mass of one PROTON is1837 times the mass of an ELECTRON . Hence the totol mass of protons in boron is 9185 times`(5xx1837)`the totalmass of ELECTRONS.

Discussion

26.	Assertion (A): The products of electrolysis of water are hydrogen and oxygen. Reason (R ): In electrolysis process of water, hydrogen ions are attracted to anode and hydroxyl ions are attracted to cathode.
Answer» Both (A) and (R ) are TRUE and (R ) is the CORRECT reason for (A). Both (A) and (R ) are true but (R ) is not the correct reason for (A) (A) is true but (R ) is false (A) is false but (R ) is true. Solution :During the electrolysis of water the electrolyte water DISSOCIATES in `H^(+)` and `OH^(-)` ions which move to cathode and anode RESPECTIVELY. Oxygen and hydrogen are produced.

Discussion

27.	Assertion (A): The Clark's method involves removal of permanent hardness. Reason (R ):The Clark's method involves the addition of slaked lime which results in the removal of bicarbonates as insoluble carbonates.
Answer» Both (A) and (R ) are true and (R ) is the correct reason for (A). Both (A) and (R ) are true but (R ) is not the correct reason for (A) (A) is true but (R ) is false (A) is false but (R ) is true. Solution :Clark's METHOD is used to REMOVE temporary hardness. In this process slaked lime is added, which RESULTS in conversion of soluble bicarbonates into INSOLUBLE carbonates. On filtration soft water is obtained.

Discussion

28.	Assertion (A) : sodium formss a monovalent ion.Reason (R ) :Sodium loses only one electron from second last shell.
Answer» Both A and R are true and R is the CORRECT explanation For A. Both A and R are true but R is not the correct explanationfor A. A is true and R is false. A is false and R is true. Solution :Sodium LOSES only one electron from its OUTER most SHELL or valence shell and forms monovalent ion.

Discussion

29.	Assertion (A) : Rate of evaporation is less in rainy season. Reason ( R) Rate of evaporation is directly proportional to humidity.
Answer» Both A and R are true and R is the CORRECT explanation for A. Both A and R are true but R is not the correct explanation for A. A is true and R FALSE. A is false and R is true. Solution :RATE of evaporation is inversely proportional to humidity. In RAINY season humidity is more. Hence rate of evaporation is LESS.

Discussion

30.	Assertion (A): Pure nitric acid on standing for long turns yellow. Reason (R): HNO_(3) undergoes decomposition and forms NO_(2).
Answer» Both A and R are true and R is CORRECT explanation for A. Both A and R are true but R is not correct explanation for A. A is true and R is false. A is false and R is true. Solution :Pure NITRIC acid on standing for long turns YELLOW due to its decomposition and the FORMATION of NO_(2), NO_(2)` imparts yellow colour.

Discussion

31.	Assertion (A): Pure H_(2)SO_(4) is colourless. Reason (R): On long standing H_(2)SO_(4) undergoes decomposition to form SO_(2).
Answer» Both A and R are true and R is CORRECT EXPLANATION for A. Both A and R are true but R is not the correct for A. A is true and R is false. Both A and R are false. Solution :Pure `H_(2)SO_(4)` is COLOURLESS. `H_(2)SO_(4)` is a stable ACID. HENCE it does not undergo decomposition on long standing.

Discussion

32.	Assertion (A): Pickles are generally not stored in tin vessels. Reason (R): Tin reacts with the acid components of pickles.
Answer» Both A and R are true and R is correct explanation for A. Both A and R are true but R is not the correct for A. A is true and R is false. A is false and R is true. Solution :Pickles are GENERALLY not stored in tin VESSELS as tin REACTS with acids present in the pickles.

Discussion

33.	Assertion (A) : Mass number of a carbon is 12.Reason ( R): Carbon possesses equal number of all three fundamental particles.
Answer» Both A and R are true and R is the correct explanation For A. Both A and R are true but R is not the correct EXPLANATIONFOR A. A is true and R is FALSE. A is false and R is true. Solution :NUMBEROF electronic , protons and neutrons in carbon are equal , that is 6.the mass number of carbon is 12.

Discussion

34.	Assertion (A): Many fuel gases contain hydrogen as a major constituent. Reason ( R): Liquid hydrogen is a very light fuel.
Answer» Both (A) and ( R) are true and ( R) is the correct EXPLANATION for (A). Both (A) and ( R) are true but (R ) is the correct explanation for (A). (A) is true but ( R) is false. (A) is false but (R ) is trues. Solution :Many fuel gases contain HYDROGEN as a major CONSTITUENT because of its HIGH CALORIFIC value.

Discussion

35.	Assertion (A): If excess of carbon is passed through lime water, it becomes transparent. Reason ( R): Calcium cicarbonate is soluble in water.
Answer» Both (A) and ( R) are ture and ( R) is the correct EXPLANATION for(A). Both (A) and ( R)are true ( R) is not the correct explanation for (A). (A) is true but ( R) is false. (A) is false but (R ) is trues. Solution :If EXCESS of carbon dioxide is dioxide is passed through lime water it becomes transparent due to the FORMATION of `Ca(HCO_(3))_(2)`.

Discussion

36.	Assertion (A): Hydrogen gas is one of the components in both oxyhydrogen flams and oxyacetylene flame. Reason ( R): Hydrogen is inflammable.
Answer» Both (A) and ( R) are ture and ( R) is the correct REASON of(A). Both (A) and ( R) are trure but ( R) is not the correct reason of (A). (A) is true but ( R) is FALSE. (A) is false but (R ) is trues. Solution :In oxyhydrogen flame, hydrogen gas is involved due to its INFLAMMABLE nature.

Discussion

37.	Assertion (A) : Gold threads are used in silk sarees. Reason (R) : Gold is highly ductile by nature.
Answer» Both (A) and (R)are TRUE and (R) is the correct reason of (A). Both (A) and (R) are true but (R) is not the correct explanation of (A). (A) is true but (R) is FALSE. (A) is false but (R) is true. Solution :In silk sarees GOLD THREADS could be used as gold is highly DUCTILE by nature.

Discussion

38.	Assertion (A) : Gold is used for making jewellery coins. Reason (R) : It is relatively hard metal.
Answer» Both (A) and (R)are true and (R) is the correct reason of (A). Both (A) and (R) are true but (R) is not the correct explanation of (A). (A) is true but (R) is false. (A) is false but (R) true. Solution :Gold is USED for MAKING jewellery COINS asgoldpossessesa yellow lusture , is MALLEABLE, ductile, soft and highly RESISTANT to chemicals.

Discussion

39.	Assertion (A): Generally pickles are stored in glass vessels and plastic vessels. Reason (R): The components of pickles are highly reactive towards glass/plastic.
Answer» Both A and R are TRUE and R is CORRECT explanation for A. Both A and R are true but R is not the correct for A. A is true and R is false. Both A and R are false. Solution :GLASS and plastic do not react with the components of pickle. Hence PICKLES are stored in glass/plastic VESSELS.

Discussion

40.	Assertion (A) : Fuse wire is made up of alloy constituted of lead and tin in 1 : 1 ratio by mass. Reason (R) : Bothlead and tin have comparatively low melting points than other metals.
Answer» Both (A) and (R)are true and (R) is the CORRECT REASON of (A). Both (A) and (R) are true but (R) is not the correct EXPLANATION of (A). (A) is true but (R) is false. (A) is false but (R) is . Solution :Fuse wire is made up of ALLOY constituted of lead andtin in ` 1 : 1` ratio by mass as bothlead andtin have comparatively LOW melting points than other metals.

Discussion

41.	Assertion (A): Electrolysis of water results in liberation of hydrogen at anode and oxygen at cathode. Reason (R ): When burning splinter is introduced in test tube at cathode, it is put off with a pop sound.
Answer» Both (A) and (R ) are true and (R ) is the correct reason for (A). Both (A) and (R ) are true but (R ) is not the correct reason for (A) (A) is true but (R ) is FALSE (A) is false but (R ) is true. Solution :In the electrolysis of water, HYDROGEN is liberated at cathode and OXYGEN is liberated at anode. When burning splinter is INTRODUCED into the test tube with hydrogen, it is put off with a pop sound.

Discussion

42.	Assertion (A) : Dogs stretch out their tongues in summer. Reason (R ) : Evaporation leads to cooling.
Answer» Both A and R are true and R is the CORRECT explanation for A. Both A and R are true but R is not the correct explanation for A. A is true and R FALSE. A is false and R is true. Solution :DOGS stretch out their tongues in summer as evaporation of the saliva leads to cooling

Discussion

43.	Assertion(A) :Copper exhibits variable valency.Reason (R ) : Copper loses two electrons from its valence shell and it can loss one moreelectron from second last shell.
Answer» Both A and R are true and R is the correct EXPLANATION For A. Both A and R are true but R is not the correct explanationfor A. A is true and R is false. A is false and R is true. Solution :COPPER loses ONE electron from its valence shell to form `Cu^(+)`and can loss one more electron from SECOND last shell to from`Cu^(2+)`ion.

Discussion

44.	Assertion (A): Boiling removes both temporary and permanent hardness from water. Reason (R ): Bicarbonates of calcium and magnesium undergoes decomposition on heating
Answer» Both (A) and (R ) are true and (R ) is the CORRECT REASON for (A). Both (A) and (R ) are true but (R ) is not the correct reason for (A) (A) is true but (R ) is false (A) is false but (R ) is true. Solution :Boiling REMOVES only temporary hardness because soluble bicarbonates of CALCIUM and magnesium undergo DECOMPOSITION on heating and insoluble carbonates are formed.

Discussion

45.	Assertion (A) : Baking soda (NaHCO_(3)) is a compound. Reason (R ) : Properties NaHCO_(3) are absolutely different from sodium, carbon, hydrogen and oxygen.
Answer» Both A and R are true and R is the correct EXPLANATION for A. Both A and R are true but R is not the correct explanation for A. A is true and R false. A is false and R is true. Solution :The constituents of baking soda that is Na, H, C and O do not retain their PROPERTIES and hence backing soda is a compound.

Discussion

46.	Asha 's mother asked her daughter Asha to boil the milk and after some time , she told Usha , Asha 's sister to add little curd in the same luke warm milk . Nextday, their father while teaching"Transformation of matter " to his daughters wanted to relate the given activity . so he asked them - " what type of changewas involved in the activities performed by you yesterday ?" Predict the answer given by them and justify.
Answer» Solution :During boiling of milk , the FAT PARTICLES being lighter than water RISE up when some amount of water vaporises . Thislayer of fat becomes thick and forms a COATING over milk is a physical change . Curdling of milk invloves partial conversion of lactose sugar into lactic acid . Since there is change in molecular composition , curdling of milk is a chemical change.

Discussion

47.	Arrange the terms in sequence of water cycle starting from water bodies. Precipitation(b) Condensation(c ) Water vapour (d) Infiltration(e) Ground water table
Answer» edbca cbade cedab ebcad Solution :(i) WATER vapour (ii) CONDENSATION (iii) Precipitation (IV) Infiltration (v) GROUND water table

Discussion

48.	Arrange the steps in sequence for the manufacture of common salt. (a)Recrystallization (b)Evaporation of sea water (c)Addition of sodium iodide and potassium iodide (d)Dissolution in water (e ) Formation of crude salt
Answer» bedac bdeac bcdae abedc Solution :(i) EVAPORATION of sea water (ii) FORMATION of CRUDE salt (iii) Dissolution in water (iv) Recrystallization (v) Addition of sodium iodide and POTASSIUM iodide and potassium iodide

Discussion

49.	Arrange the suitable steps in correct sequence for the manufacture of sodium chloride from sea water. (a)Making of hot saturated solution (b)Evaporation (c)Recrystallization (d) Collection fo sea water (e ) Addition of small quantity of sodium iodide or potassium iodide
Answer» deba debc deabc dbac SOLUTION :(i) COLLECTION of SEA WATER (ii) Evaporation (iii) Making of hot saturated solution (iv) Recrystallization.

Discussion

50.	Arrange the steps in sequence for the manufacture of cement in process. (a) Formation of clinker (b) Pulverization (c) Additon of gypsum (d) Heating to high temperature (1500^(@)C" to " 1600^(@)C)
Answer» bdac badc bcda bcad Solution :(i) PULVERIZATION (ii) HEATING to high temperature `(1500 ^(@) C "to" 1600^(@)C)` (iii) FORMATION of CLINKERS (iv) Addition of gypsum

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Calculate the number of neutrons in the following.(a)._(15)X^(31)(b)._(92)"U"^(235)(c )._(19)"K"^(39)

Calculate the amount of heat energy required to increase the temperature of 10 g of water through 12^(@)C.

Calcium hydroxide on heating gives a solid product 'X' and on treatment with hydrochloric acid gives another solid product Y. What do you observe whe X and Y are exposed to atmosphere? Explain.

Calcium hydroxide is added to soils before applying fertilisers. Justify the purpose.

Calassify the chemical reactions into varous types depending on the way the products are formed by giving suitable examples.

CaC1_(2) is an example of

Both the formation of mist and clouds involve the condensation of water vapour. In which aspect do they differ from each other ?

Both protons and neutrons possess thesame magnitude of charge but opposite signs.

Both galvanizing and tinning are adopted for preventing of iron but only tinned iron containers are used to preserve food material. Justify.

Boiling point is the temperature at which _______ is converted to ________ at one atmospheric pressure.

Blue vitriol is used as a fungicide for grape plants.

Blue coloured solid anhydrous cobalt chloride is exposed to atmosphere and forms pink coloured solid. From this, we can infer that cobalt chloride is

Between H_(2)SO_(4) "and" H_(3)PO_(4), which solution possesses greater number of H^(+) ions in the given volume assuming that the number of molecules of both acids are equal? Give reasons.

Balance the following chemical equations.(i)NH_(3)+Br_(2)toN_(2)+NH_(4)Br(ii)FeS_(2)+O_(2)toFe_(2)O_(3)toSO_(2)

Balackening of silverware is a ____________ change.

Baking soda (NaHCO_(3)) is a compound because

Bakelite is an example of ________ plastic.

Auroras appear in the layer of atmosphere which is known as …………

Atomicity of ozone is _________ .

Atomic number of a metal having 12 neutrons and mass number 23 is __________ .

Assme that temperature is recorded in the termosphere with the help of a thermometer. You will be amazed to find that the temperature recorded in will be extremely low. This is because

Assertion (A): When carbon dioxide gas is passed through lime water, lime water is turned milky. Reason (R): Calcium carbonate is soluble in water.

Assertion (A) : Washing soda (Na_(2)CO_(3)) is a compounds. Reason (R ) : Sodium retains its property in washing soda.

Assertion (A) : Tin is used in the manufacture of fusible alloys. Reason (R) : Tin is a good conductor of electricity.

Assertion (A) : The total mass of the protons of a born atom is 6185 times the total mass of electrons.Reason (R ) : Mass of one proton is times the mass of electron.

Assertion (A): The products of electrolysis of water are hydrogen and oxygen. Reason (R ): In electrolysis process of water, hydrogen ions are attracted to anode and hydroxyl ions are attracted to cathode.

Assertion (A): The Clark's method involves removal of permanent hardness. Reason (R ):The Clark's method involves the addition of slaked lime which results in the removal of bicarbonates as insoluble carbonates.

Assertion (A) : sodium formss a monovalent ion.Reason (R ) :Sodium loses only one electron from second last shell.

Assertion (A) : Rate of evaporation is less in rainy season. Reason ( R) Rate of evaporation is directly proportional to humidity.

Assertion (A): Pure nitric acid on standing for long turns yellow. Reason (R): HNO_(3) undergoes decomposition and forms NO_(2).

Assertion (A): Pure H_(2)SO_(4) is colourless. Reason (R): On long standing H_(2)SO_(4) undergoes decomposition to form SO_(2).

Assertion (A): Pickles are generally not stored in tin vessels. Reason (R): Tin reacts with the acid components of pickles.

Assertion (A) : Mass number of a carbon is 12.Reason ( R): Carbon possesses equal number of all three fundamental particles.

Assertion (A): Many fuel gases contain hydrogen as a major constituent. Reason ( R): Liquid hydrogen is a very light fuel.

Assertion (A): If excess of carbon is passed through lime water, it becomes transparent. Reason ( R): Calcium cicarbonate is soluble in water.

Assertion (A): Hydrogen gas is one of the components in both oxyhydrogen flams and oxyacetylene flame. Reason ( R): Hydrogen is inflammable.

Assertion (A) : Gold threads are used in silk sarees. Reason (R) : Gold is highly ductile by nature.

Assertion (A) : Gold is used for making jewellery coins. Reason (R) : It is relatively hard metal.

Assertion (A): Generally pickles are stored in glass vessels and plastic vessels. Reason (R): The components of pickles are highly reactive towards glass/plastic.

Assertion (A) : Fuse wire is made up of alloy constituted of lead and tin in 1 : 1 ratio by mass. Reason (R) : Bothlead and tin have comparatively low melting points than other metals.

Assertion (A): Electrolysis of water results in liberation of hydrogen at anode and oxygen at cathode. Reason (R ): When burning splinter is introduced in test tube at cathode, it is put off with a pop sound.

Assertion (A) : Dogs stretch out their tongues in summer. Reason (R ) : Evaporation leads to cooling.

Assertion(A) :Copper exhibits variable valency.Reason (R ) : Copper loses two electrons from its valence shell and it can loss one moreelectron from second last shell.

Assertion (A): Boiling removes both temporary and permanent hardness from water. Reason (R ): Bicarbonates of calcium and magnesium undergoes decomposition on heating

Assertion (A) : Baking soda (NaHCO_(3)) is a compound. Reason (R ) : Properties NaHCO_(3) are absolutely different from sodium, carbon, hydrogen and oxygen.

Arrange the terms in sequence of water cycle starting from water bodies. Precipitation(b) Condensation(c ) Water vapour (d) Infiltration(e) Ground water table

Arrange the steps in sequence for the manufacture of common salt. (a)Recrystallization (b)Evaporation of sea water (c)Addition of sodium iodide and potassium iodide (d)Dissolution in water (e ) Formation of crude salt

Arrange the suitable steps in correct sequence for the manufacture of sodium chloride from sea water. (a)Making of hot saturated solution (b)Evaporation (c)Recrystallization (d) Collection fo sea water (e ) Addition of small quantity of sodium iodide or potassium iodide

Arrange the steps in sequence for the manufacture of cement in process. (a) Formation of clinker (b) Pulverization (c) Additon of gypsum (d) Heating to high temperature (1500^(@)C" to " 1600^(@)C)

Boiling point is the temperature at which _ is converted to __ at one atmospheric pressure.