908 + Interview Questions in Chemistry in Class 7

1.	Which among the following is the application of neutralization?
Answer» Farmers add slaked lime to soil. Persons suffering from acidity are given antacid tablets. Usage of lithium HYDROXIDE in submarines. All of above. Solution :The PROCESS due to which an acid completely reacts with a base to FORM SALT and water as the only products is called neutralization. Add slaked lime to soil to neutralize the acidity of the soil. Persons suffering from acidity are given antacid tablets like `Mg(OH)_(2)` to neutralize acidity. Submariners in submarine and ASTRONAUTS in spaceships, use lithium hudroxide to neutralize `CO_(2)` which is exhaled.

Discussion

2.	Two molecules of sulphur trioxide are indicated by________.
Answer» SOLUTION :`2SO_(3)` `2SO_(3)` MEANS 2 MOLECULES of `SO_(3)`.

Discussion

3.	What is photolytic decomposition ? Give an example.
Answer» SOLUTION :A CHEMICAL decomposition reaction which takes place in presence of light is CALLED photolytic decomposition reaction. Example : `2HOCl to2HCl +O_(2)`

Discussion

4.	Which among the following substances has the strongest intermolecular forces of attraction?
Answer» Steam Bromine Oxygen Hydrogen CHLORIDE gas Solution :Bromine is a liquid and HENCE it possesses stronger INTERMOLECULAR forces of ATTRACTIONS.

Discussion

5.	The volumetric composition of water is
Answer» `1 : 2` RATIO of hydrogen and OXYGEN respectively `1 : 8` ratio of hydrogen and oxygen respectively `1 : 1` ratio of hydrogen and oxygen `2 : 1` ratio of hydrogen and oxygen respectively Solution :The volumetric COMPOSITION of water is 2 : 1 of hydrogen and oxygen.

Discussion

6.	Which of the following properties of silicon is not exploited in the manufacture of non-stick cookware ?
Answer» High resistance to heat POOR electrical conductivity Non-stick nature High resistance to chemiclas SOLUTION :Silicone is a bad CONDUCTOR of electricity and this property is not EXPLOITED in the manufacture of non-stick cookware.

Discussion

7.	The salt formed by complete neutralization of calcium hydroxide with ic acid of sulphur having four oxygen atoms is
Answer» CALCIUM sulphite calcium bisulphate calcium sulphate calcium bisulphite Solution :ic ACID of sulphur with four OXYGEN atoms is `H_(2)SO_(4)` `H_(2)SO_(4) + Ca(OH)_(2) UNDERSET(("Calcium sulphate"))(rarr CaSO_(4) + 2H_(2)O)`

Discussion

8.	Which of the following is the most suitable for the construction of a pillar ?
Answer» Cement MORTAR Concrete RCC Pure cenment Solution :RCC is very strongbecause of the presence of structural steel inside it. HENCE, it is most SUITABLE for theconstructionof pillars.

Discussion

9.	Which among the following gas was called former ?
Answer» NITROGEN HYDROGEN Carbon dioxide Oxygen Solution :Oxygen GAS is called ACID former.

Discussion

10.	The thermal expansion of solids is the least among the three states of matter. Explain.
Answer» Solution :In solid, STRONG intermolecular forces of attractions are present between the MOLECULES DUE to which they EXPAND less on heating.

Discussion

11.	Vish went to an electrical shop along with her father to purchase a bulb and some electrical equipment. After returning home, Vish looking at the bulb keenly and asked her father. "Is it filled with air or vacuum?" Her father told her that it was filled with nitrogen or argon. She asked him why the bulb could not be filled with air which is readilyavailable, as nitrogen is obvioslu a part of air ? What was her father's correct explanation to her question ?
Answer» Solution :Air cannot be filled in electric bulbs as air CONTAINS oxygen which oxidizes the filament Hence inert gas lile AR or less reactive gases LIKE NITROGEN are used as it doesn't react with METAL filament.

Discussion

12.	Which among the following liquids has the highest specific heat?
Answer» Petrol Mercury Oil WATER Solution :Water has the HIGHEST specific heat among all the substances.

Discussion

13.	Which compound of silicon is used for the preservation of eggs ?
Answer» SOLUTION :Sodium SILICATE is USED for the PRESERVATION of EGGS.

Discussion

14.	Two non-metallic oxides 'A' and 'B' are produced by buring of fossil fuels 'A' pollutes both air and water. 'B' does not cause water pollution and its presentce in water is essential. It causes air pollution. Idendify A and B.
Answer» `NO_(2),SO_(2)` `SO_(2),CO` `SO_(2),CO_(2)` `CO_(2),NO_(2)` Solution :A' can be `SO_(2)" or "NO_(2)` because they pollute air and cause acid rain to pollute water. 'B' can be `CO_(2)` since it does not cause acid rain. Its presence in water is ESSENTIAL for aquatic plants. It is considered as an air POLLUTANT as it RESULTS in global warming.

Discussion

15.	What is annealing ?
Answer» SOLUTION :Thecooling of molten GLASS at controlled temperature is CALLED ANNEALING.

Discussion

16.	Which of the following is obtained as a byproduct in the manufacture of soap ?
Answer» Glycerine Sodium hydroxide VEGETABLE oil Salt of FATTY acid SOLUTION :Glycerine is obtained as abyproduct in the manufacture of SOAP.

Discussion

17.	When Vasu was running high temperature her mother was nursing him by placing wet cloth on his forehead till temperature has gone down. Justilfy what purpose did the mother's action serve.
Answer» Solution :Evaporation is the process of conversion of liquid into gas. During this process the energy required for the conversion of liquid into gas is taken from the SURROUNDINGS, as a RESULT, the temperature of the surroundings decreases that is evaporation causes cooling. When WET cloth is PLACED on the forehead, water present in the cloth slowly undergose evaporation and hence temperature of the body decreases.

Discussion

18.	Which of the following applications of copper require refining of copper instead of alloying?
Answer» Making statues Making household utensils Making SHELLS of ammunitions Making electric transmission cables. Solution :PURE COPPER is REQUIRED to manufacture electric transmission cables.

Discussion

19.	The two metals involved in the galvanization process are
Answer» iron and copper iron and zinc zinc andcopper copper and aluminium Solution :The process of COATING zinc over iron to PREVENT resting is called GALVANIZATION.

Discussion

20.	Which ofthe following is not achemical change ?
Answer» Passing of steam over redhot coke. Change in the COLOUR of dilute nitric acid upon LONG standing. Absorption of moisture by `P_(2)O_(5)`. Absorption of moistureby `CaCl_(2)` . Solution :ANHYDROUS`CaCl_(2)` , absorbs moisture TILL it becomes saturated and changes its physical state . Hence it is a deliquencent substance.

Discussion

21.	Which of the following water is suitable for drinking?
Answer» SOFT water Demineralized water Potable water Distilled water Solution :Potable water is SUITABLE for drinking purpose.

Discussion

22.	The scullptures and monuments get damged due to acid rains. Usage of scrubbers, containing lime water, in indestries decreases the percentage content of the major air pollutants that contribute to acid rain. The characteristic reaction incolved in the surbber is
Answer» neutrazation oxidation reduction combination followed by decompositon. Solution :Marble is made of `CaCO_(3)` which gets dissolved when it reacts with acids like `H_(2)SO_(4)" or "HNO_(3)` of acid rains. The MAJOR pollutants which contribute to acid rain `(NO_(2)" and "SO_(2))` RELEASED into atmosphere. The `NO_(2)" and "SO_(2)` percentage CONTENT in the atmosphere can be decreasede by using equipment like scrubbers. In a SCRUBBER, lime water is taken which combines with `SO_(2)" to form "CaSO_(3)` which is removed as slurry. Hence it is a neutraliztion reaction. `underset("base")(Ca(OH)_(2))+underset("acid gas")(SO_(2)toCaSO_(3))+H_(2)O`

Discussion

23.	What happens when potassium nitrate is subjected to heating ?
Answer» SOLUTION :It decomposes to GIVE `KNO_(2)` and OXYGEN. `KNO_(3)toKNO_(2)+O_(2)uarr`

Discussion

24.	Water sticks to due to __________
Answer» ADHESIVE forces between WATER and GLASS. cohesive forces between water and glass. cohesive forces between water molecules. cohesive forces between glass molecules. Solution :Water STICKS to glass due to adhesive forces acting between water and glass.

Discussion

25.	X is an atom of an element in which 4th shell is the valence shell and the number of electrons are in 1 : 1 ratio in 1st, 4th and 2nd, 3rd shells respectively. Its corresponding oxide Y on hydrolysis gives Z. Explain the changes that take place when phenolphthalein and methyl orange are added to Z separately.
Answer» Solution :As the element burns with a brick red flame, it is calcium with electronic configuration 2, 8, 8, 2 `underset(("X"))(Ca) + O_(2) RARR underset(("Y"))(CAO)` `underset(("Y"))(CaO) + H_(2)O rarr underset(("Z"))(Ca(OH)_(2))` As `Ca(OH)_(2)` is basic in NATURE it turns phenolphthalein PINK and methyl orange yellow.

Discussion

26.	Xenon and krypton is used in electricbulbs to slow down the__________ of tungsten.
Answer» Solution :SUBLIMATION Xenon and KRYPTON is USED in electric bulbs to SLOW down the sublimation of tungsten.

Discussion

27.	What is alloying ?
Answer» Solution :The process of mixing of a particular metal uniformaly with quatities of different metals in their MOLTEN STATE in order to improve the MECHANICAL properties of the metal is called alloying.

Discussion

28.	Write formulae and names of the various salts formed when magnesium hydroxide is treated with sulphurous acid.
Answer» Solution :`Mg(OH)_(2)` is a diacidic base and `H_(2)SO_(3)` is a dibasic ACID. HENCE there is possibility of three different salts. `Mg(OH)_(2) + H_(2)SO_(3) rarr underset("MAGNESIUM hydroxy bisulphite")(Mg(OH)HSO_(3) + H_(2)O)` `Mg(OH)HSO_(3) + H_(2)SO_(3) rarr underset("Magnesium bisulphite")(Mg(HSO_(3))_(2) + H_(2)O)` `Mg(OH)_(2) + H_(2)SO_(3) rarr underset("Magnesium bisulphite")(Mg(HSO_(3))_(2) + H_(2)O)` `Mg(HSO_(3))_(2) + Mg(OH)_(2) rarr underset("Magnesium sulphite")(2MgSO_(3) + 2H_(2)O)`

Discussion

29.	The trapping of solar heat energy by certain gaseous molecules present in the earth's atmophere is called………..
Answer» Solution :GREEN house effect The TRAPPING of solar hear energy by energy by certain GASEOUS molecules present in the EARTH's atmosphere is called green house effect.

Discussion

30.	Which of the gas is the most unsuitable forfilling up weather observation balloons?
Answer» HELIUM Neon Hydrogen ARGON Solution :Argon is unsuitable for filling upweather OBSERVATION BALLOONS because it is heavier than air.

Discussion

31.	What is the role of calcium hydroxide used in making mortar and white washing?
Answer» Solution :Mortar is a mixture of CALCIUM hydroxide, sand and water. On exposure to atmosphere calcium hydroxide reacts with`CO_(2) "forming" CaCO_(3)` which is a HARD SUBSTANCE and hence strengthens the construction. `Ca(OH)_(2)` is used for white washing because of the formation of white coloured `CaCO_(3)` substance.

Discussion

32.	What are the human activites that contribute to air pollution ?
Answer» Solution :HUMAN ACTIVITIES responsible for air pollution are (i) buring of fossil fuels. (ii) deforestation (III) emission of polluted gases from vehicles. (iv) AGRICULTURAL activities which involves usage of fertilizers, pesticides etc. (v) lack of civic SENSE by the people.

Discussion

33.	Which of the following is not an alloy ?
Answer» Brass Bronze Magnalium MAGNESIUM Solution :Magnesium is an ELEMENT.

Discussion

34.	Three naturally occurring elements X,Y and Z are good conductors of electricity and are very precious. Z is more reactive than X and Yand on exposure to air for a long time turns black. Z forms analloy withY and is used in jewellery and Xis used as a catalyst. Identify X , Y and Z.
Answer» Solution :THREE precious elements that OCCUR nature are silver, GOLD and platinum. Silver is more reactive than gold and platinum is used as a CATALYST. Alloy of gold with silver is used in jewellery. So X is platinum, Y is gold and Z si silver.

Discussion

35.	Which of the following dissolved gases are present in drinking water?
Answer» Oxygen, nitric oxide Oxygen, CARBON monoxide Oxygen, carbon dioxide Oxygen, nitrogen Solution :Oxygen and carbon dioxide are the two DISSOLVED gases PRESENT in DRINKING WATER.

Discussion

36.	Thermal pollution of water leads to the death of biotic life. Explain.
Answer» Solution :Thermal pollution of water is due to HEAVY industries such as STEEL, thermal power plants. These sources DISCHARGE large amounts of hot water into the rivers, which helps in the rapid growth of alage. This algae depletes dissolved OXYGEN in water. This in turn leads to the death of biotic life.

Discussion

37.	Underground water is free from suspended impurities.
Answer» Solution :Under GROUND water is passed through several LAYERS of SOIL HENCE it is FREE from suspended impurities.

Discussion

38.	X ana Y are gases at room temperature. X is less rective and is used to preserve food matrial, while 'Y' is required for combustion. Metal 'M' gets corroded when it combines with 'Y' in the presence of 'Z'. An atom of 'M' possesses 14 electrons in the second last shell and N is the shell.Identify X, Y, Z and M.
Answer» SOLUTION :14 electrons in M shell and 2 electrons in N shell corresponds to metal 'Fe'. X is nitrogen which is FILLED in air tight food packets to prevent oxidation and Y is oxygen which is required for combusion. In presence of oxygen and water vapour (Z) metal IRON (M) GETS ruted to form a compound that is `Fe_(2)O_(3).XH_(2)O.` X = nitrogen Y = oxygen, Z = water vapour and M = Fe.

Discussion

39.	Which of the following fertilizers cannot replenish nitrogen?
Answer» Super phosphate of LIME (calcium DIHYDROGEN phosphate with GYPSUM) Nitre Ammonium sulphate Triammonium phosphate Solution :SUPERPHOSPHATE of lime cannot proide nitrogen.

Discussion

40.	The valency of helium is zero.
Answer» SOLUTION :True HELIUM possesses stable duplet configuration with 2 electrons on I shell . Henceits valency is ZERO.

Discussion

41.	The valency of argon is ________.
Answer» SOLUTION :ZERO The VALENCY of ARGON is zero.

Discussion

42.	Water containing calcium bicarbonate produces ______ with soap.
Answer» Solution : WATER CONTAINING bicarnonate produces SCUM with SOAP.

Discussion

43.	Zincite is obtained by heating ________
Answer» Solution :ZINC CARBONATE Zincite is OBTAINED by HEATING zinc carbonte.

Discussion

44.	What is emulsification ?
Answer» Solution :Thephenomenon of REMOVEL of DIRT by THEFORMATION of emulsion with SOAPS and detergent is called emulsification.

Discussion

45.	Water containing calcium bicarbonate produces scum with soap.
Answer» Solution :Soft WATER produces LATHER with soap WHEREAS HARD water produces scum with soap.

Discussion

46.	Washing soda (Na_(2)CO_(3)) is a compound because the constituents combine
Answer» CHEMICALLY in fixed RATIO by weight chemically in any ratio by weight. physically in fixed ratio by weight. physically in any ratio by weight. Solution :In washing soda `(Na_(2)CO_(3))`, the constituents are combined chemically in fixed ration of their weights and hance it is a COMPOUND.

Discussion

47.	Which among the following is/are poor conductors of electricity?
Answer» CONCENTRATED and pure `H_(2)SO_(4)` Concentrated and pure `HNO_(3)` Liquid hydrogen chloride All the above Solution :ACIDS act as GOOD conductors of electricity when they are in the ionized state. Concentrated and pure `H_(2)SO_(4)`, concentrated and pure `HNO_(3)` and liquefied HCI do not ionize and hence are bad conductors of electricity.

Discussion

48.	Which among the following is based on the principle that boiling point decreases with decrease in atmosphere pressure?
Answer» COOKING food at sea-level takes longer period of TIME Cooking food at HIGHER altitudes takes longer period of time Working principle of air coolers Working of pressure cooker. Solution :As we move to higher altitudes, pressure decreases and hence boiling point decreases. Water boils at low temperatures on the HILLS andthus the cooking of food takes longer time.

Discussion

49.	Wealthy but not healthy agriculture can be achieved by
Answer» introducing biogas plants using NATURAL pesticides such as neem oil. using drip irrigation using artifical FERTILIZERS. Solution :By introducing artifical fertilizers, crop yield is IMPROVED but at the same time it contributes to WATER pollution.

Discussion

50.	What is an aquifer?
Answer» Solution :Below the WATER table, there is an UNDERGROUND layer of water BEARING permeable rock of unconsolidated materials from which ground water can be usefully extracted using a water well. This is CALLED AQUIFER.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Which among the following is the application of neutralization?

Two molecules of sulphur trioxide are indicated by________.

What is photolytic decomposition ? Give an example.

Which among the following substances has the strongest intermolecular forces of attraction?

The volumetric composition of water is

Which of the following properties of silicon is not exploited in the manufacture of non-stick cookware ?

The salt formed by complete neutralization of calcium hydroxide with ic acid of sulphur having four oxygen atoms is

Which of the following is the most suitable for the construction of a pillar ?

Which among the following gas was called former ?

The thermal expansion of solids is the least among the three states of matter. Explain.

Which among the following liquids has the highest specific heat?

Which compound of silicon is used for the preservation of eggs ?

Two non-metallic oxides 'A' and 'B' are produced by buring of fossil fuels 'A' pollutes both air and water. 'B' does not cause water pollution and its presentce in water is essential. It causes air pollution. Idendify A and B.

What is annealing ?

Which of the following is obtained as a byproduct in the manufacture of soap ?

When Vasu was running high temperature her mother was nursing him by placing wet cloth on his forehead till temperature has gone down. Justilfy what purpose did the mother's action serve.

Which of the following applications of copper require refining of copper instead of alloying?

The two metals involved in the galvanization process are

Which ofthe following is not achemical change ?

Which of the following water is suitable for drinking?

The scullptures and monuments get damged due to acid rains. Usage of scrubbers, containing lime water, in indestries decreases the percentage content of the major air pollutants that contribute to acid rain. The characteristic reaction incolved in the surbber is

What happens when potassium nitrate is subjected to heating ?

Water sticks to due to __________

Xenon and krypton is used in electricbulbs to slow down the__________ of tungsten.

What is alloying ?

Write formulae and names of the various salts formed when magnesium hydroxide is treated with sulphurous acid.

The trapping of solar heat energy by certain gaseous molecules present in the earth's atmophere is called………..

Which of the gas is the most unsuitable forfilling up weather observation balloons?

What is the role of calcium hydroxide used in making mortar and white washing?

What are the human activites that contribute to air pollution ?

Which of the following is not an alloy ?

Three naturally occurring elements X,Y and Z are good conductors of electricity and are very precious. Z is more reactive than X and Yand on exposure to air for a long time turns black. Z forms analloy withY and is used in jewellery and Xis used as a catalyst. Identify X , Y and Z.

Which of the following dissolved gases are present in drinking water?

Thermal pollution of water leads to the death of biotic life. Explain.

Underground water is free from suspended impurities.

Which of the following fertilizers cannot replenish nitrogen?

The valency of helium is zero.

The valency of argon is ________.

Water containing calcium bicarbonate produces ______ with soap.

Zincite is obtained by heating ________

What is emulsification ?

Water containing calcium bicarbonate produces scum with soap.

Washing soda (Na_(2)CO_(3)) is a compound because the constituents combine

Which among the following is/are poor conductors of electricity?

Which among the following is based on the principle that boiling point decreases with decrease in atmosphere pressure?

Wealthy but not healthy agriculture can be achieved by

What is an aquifer?