908 + Interview Questions in Chemistry in Class 7

1.	What is meant by synthesis reaction ? Given an example.
Answer» SOLUTION :Synthesis is a combination chemical REACTION in which two ELEMENTS combine to give one SINGLE compound. Example`H_(2)+Cl_(2)to2HCl`

Discussion

2.	What is the latent heat of fusion and latent heat of vapourization of 10 g of ice and water resepectively?
Answer» 800 cal, 800 cal 540 cal, 540 cal 800 cal, 5400 cal 540 cal, 800 cal Solution :LATENT HEAT of fusion of 10 g of ice is `10 xx 80` = 800 cal Latent heat of vapourization of 10 g of water is `10 xx 540` = 5400 cal

Discussion

3.	Which of the following food items provides the maximum energy ?
Answer» VEGETABLE oil GLUCOSE Cereals PULSES Solution :Vegetable oil is a fat and it PROVIDES the maximum energy.

Discussion

4.	Which of the following chemical change is a photolytic decomposition reaction?
Answer» DECOMPOSITION of HOCl on standing. Formation of hydrogen chloride from their CONSTITUENT elements. Decomposition of limestone . Both 1 and 2. Solution :Decomposition of limestone TAKES place at higher temperatures . Henceit is a thermal decomposition REACTION . Formation of HCltakes place in presence of light . But it is not a decomposition reaction. HOCl on standing in presence of light decompose to give HCL and `O_(2)`.

Discussion

5.	Though fat provides the maximum amount of energy, it forms a minor part ofour diet while a large part of diet contains carbohydrates?
Answer» Solution :Both FATS and carbohydrates are energy giving food NUTRIENTS and bothcontain CARBON, hydrogen and oxygen, but the molecularstructure of fat is more complex than that of carbohydrates. Carbohydrates breaks down to form carbon dioxide and water and water and releases energy. Combustion of fat takes a long period of time and hence carbohydrates are preferable to fats. Fats are considered as reservoirs of energywhile carbohydrates serveserve as instant SOURCE of energy.

Discussion

6.	Which among the following is used to remove moisture from the surroundings?
Answer» Calcium chloride Magnesium chloride Zinc chloride Calcium OXIDE Solution :Calcium oxide is a hygroscopic SUBSTANCE and HENCE it is used to remove MOISTURE from the surroundings.

Discussion

7.	Which among the following pairs of elements forms cation and anion respectively ?
Answer» SULPHUR and neon Chlorine and sodium Potassium and phosphorus Aluminum and lithium Solution :Potassium loses one electron to form CATION and phosphorous GAINS THREE electrons to form anion.

Discussion

8.	Which among the following is a detergent?
Answer» SODIUM STEARATE Sodium chloride Sodium carbonate Sodium lauryl sulphate Solution :EXAMPLE of detergent is sodium lauryl sulphate.

Discussion

9.	Which of the following is not a chemical change?
Answer» Passing of steam over redhot coke. Colour change 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 . Henceit is a deliquescent substance.

Discussion

10.	What is the latent heat of fusion and latent heat of vapourisation of 10 g of ice and water respectively?
Answer» 800 cal, 800 cal 540 cal, 540 cal 800 cal, 5400 cal 540 cal, 800 cal Solution :LATENT heat of FUSION of 10 G of water is `10 xx 80 = 800` cal Latent heat of vapourisation of 10 g of steam is `10 xx 540` = 5400 cal

Discussion

11.	What is meant by thermal decomposition ? Give an example.
Answer» SOLUTION :The chemical DECOMPOSITION which TAKES PLACE in presence of heat is called thermal decomposition. Example : `2PB(NO_(3))_(2)to2PbO+4NO_(2)+O_(2)`

Discussion

12.	What is depletion of water table?
Answer» Solution :When there is an imbalance between UNDERGROUND WATER and its replenishment the level of water table MAY GO down. This is called depletion of water table.

Discussion

13.	What is the difference between element and compounds ?
Answer» Solution :An element is a substance which is constituted of only ONE kind of atoms and cannot be further DIVIDED by any physical or chemical means. A compound is a substance which is FORMED due to the chemical COMBINATION of TWO or more elements a definite proportion by mass.

Discussion

14.	What is the action of litmus on oxygen ?
Answer» SOLUTION :OXYGEN is NEUTRAL TOWARDS LITMUS.

Discussion

15.	What are the different kinds of soap? What are the raw materials used for the manufacure of different kinds of soap? Mention their applications.
Answer» SOLUTION :

Discussion

16.	The salts of which among the pairs of metals cause greater water pollution?
Answer» Calcium, ALUMINIUM Mercury, cadmium Calcium, cadmium Calcium, mercury Solution :salts of mercury and cadmium cause GREATER WATER pollution.

Discussion

17.	What is meant by rain water harvesting?
Answer» Solution :UTILIZING the rian water to RECHARGE the GROUND water is called water harvesting or rain water harvesting.

Discussion

18.	What is diffusion ? Give one application.
Answer» Solution :The MOVEMENT of gas MOLECULES from HIGHER concentration to lower concentration is called DIFFUSION. Example : SPREADING of perfume.

Discussion

19.	Y' is obtained by the decomposition of a substance 'X'. Oxygen present in 'X' is univalent. 'Y' reacts with a neuteral oxide and evolves 'Z' which is composed of reddish brown fumes which turns moist blue litmus red. Identify 'X', 'Y' and 'Z'.
Answer» `H_(2)O_(2),H_(2)" and "CO_(2)` `H_(2)O_(2),O_(2)" and "NO_(2)` `KCIO_(3),Cl_(2)" and "O_(2)` `HgO,O_(2)" and "NO` Solution :`underset((X))(H_(2)O_(2))toH_(2)O_(2)+O_(2)` `underset((Y))(NO)+O_(2)tounderset((Z))underset(("reddish brown"))(NO_(2))` `O_(2)`(Y) is NEUTRAL towards litmus while `NO_(2)` is ACIDIC and HENCE turns MOIST bule to red

Discussion

20.	Which of thefollowing fertilizers replenishes only one essential among nitrogen, phosphorus
Answer» Potassium NITRATE Triammonium PHOSPHATE Potassium bisulphate All the above. SOLUTION :Potassium bisuphate REPLENISHES only potassium to the soil.

Discussion

21.	What are fertilizers? How are they classified ? Explain the classification of fertilizers with an example.
Answer» Solution :Fertilizers are compounds or mixtures of compounds which are added to the soil in order to provide theessential nutrients to the PLANTS. Fertilizers can be categorized into two TYPE depending on the source from which they are obtained. (i) natural fertilizer and(ii) artificial fertilizer. Natural fertilizer : Example ofnatural fertilizer is manure. The excreta of live stock and human being is mixed with straw and then the mixture is buried deep into the pits for few months. The mixture decomposes there and manure is obtained. The manure is RICH in the nutrients required for the growth of the plants. Artificial fertilizer : Artificial fertilizers are the chemical compounds manufactured in the industries. They CONTAIN one or more essential nutrients required for thegrowth of the plant. Artificial fertilizers can further be classified depending on their chemical composition i.e. theessential nutrient (s) they contian. (i) Nitrogenous fertilizers : These fertilizers replenish the deficiency of nitrogen. Calcium ammoniumnitrate, ammonium SULPHATE, basic calciumnitrate and urea aer the examples of nitrogenous fertilizers. (ii) Phosphatic fertilizers : These fertilizers replenish the deficiency of phosphorus. Trianmmonium phosphate and superhosphate of lime are the examples of phosphatic fertilizers. (iii) Potash fertilizers : These fertilizers replenish the deficiency of potassium. Potassium nitrate, potassium sulphate and potassium chloride are the examples of potash fertilizers.

Discussion

22.	Which among the following metals is the most suitable to be used as telecommunication cable?
Answer» ALUMINIUM Tin Iron COPPER Solution :ELECTRICAL CONDUCTIVITY of copper is the MAXIMUM.

Discussion

23.	Whichof thefollowing steps is not involved in the preparation of sodium chloride from sea water ?
Answer» EVAPORATION DISSOLUTION in WATER Recryztalllization Distillation Solution :The process of distillation is not INVOLVED in the EXTRACTION of sodium chloride from sea water.

Discussion

24.	Which of the following chemicals leads to water pollution?
Answer» Fertilizers INSECTICIDES Pesticides All the above Solution :Fertilizers, insecticides, and pesticides CONSIST of chemicals added during AGRICULTURAL activities. When these are let into water bodies they harm the auatic life and if this water is used for drinking purpose it affects human SYSTEM.

Discussion

25.	Which of the following pair is a major contributor to global warming ?
Answer» Carbon dioxide, nitrogen oxide Methane, WATER vapour Carbon dioxie, ozone Carbon dioxide, water vapour Solution :`CO_(2)` and watervapour are GIVEN house green house GASES present in atmosphere. Their percentage increase in atmosphere increases thetemperature of the earth and contributes to GLOBAL warming. These are the MAJOR contributors to global warming.

Discussion

26.	Which of the following elements is used for the purification of surface water to make it free from germs so that it can be used for drinking purpose?
Answer» Oxygen Flourine Chlorine Carbon Solution :Chlorine is INVOLVED in making SURFACE water potable by the process CALLED CHLORINATION.

Discussion

27.	While a teacher was her class about air and oxygen she emphasized the importance of nitrogen in the atmosphere. A student named Vivek asked the teacher-"What would happen if the percentages of nitrogen and oxygen were interchanged in the atmosphere?" The teacher praised him for the question and explained it. What was the teacher's explanation ?
Answer» Solution :Increased levels of oxygen increases the RATE of RESPIRATION which WOULD affect the human SYSTEM.

Discussion

28.	What do youmean bygrouting? Where does this technique find application ?
Answer» SOLUTION :Grouting is a TECHNIQUE used in construction activities . Pure cement or cement mixed with sand and WATER in definite proportion is applied in thegaps of construciton MATERIAL like bricks, the tiles etc., for making the surface smooth and strengthening the STRUCTURE.

Discussion

29.	Which of the following types of water does not contain dissolved gases such as oxygen and carbon dioxide?
Answer» Potable water Distilled water Saline water Soft water Solution :Potable water, soft or SEA water contain DISSOLVED gases such as oxygen and carbon DIOXIDE but distilled water does not contain `O_(2)` and `CO_(2)` because during distillation these dissolved gases are distilled off.

Discussion

30.	Which of the following water does not contain dissolved gases such as oxygen and carbon dioxide?
Answer» POTABLE water Distilled water SALINE water Soft water Solution :Potable water, soft water and SEA water CONTAIN dissolved gases such as oxygen andcarbon DIOXIDE but distilled water does not contain `O_(2)` and `CO_(2)` because during distillation these dissolved gases are distilled off.

Discussion

31.	Two salts "X" and "Y" are taken in two test tubes "A" and "B" respectively and subjected to heating Water is added to two test tubes, in case of "A" salt regains its original colour and in case of "B" water starts boiling. Then X and Y may be respectively
Answer» Blue VITRIOL and limestone blue vitriol and BAKING soda nitre and limestone nitre and WASHING soda Solution :X is blue vitriol `CuSO_(4)5H_(2)O` which is blue in colour. This on heating loses water of CRYSTALLIZATION and forms anhydrous salt which is colourless. When water is added to anhydrous salt it forms copper SULPHATE pentahydrate which is blue in colour. `underset("Blue")(CuSO_(4)5H_(2)O overset("heating") rarr underset("Colourless")(CuSO_(4)) overset(+H_(2)O) rarr underset("blue")(CuSO_(4)*5H_(2)O)` Y is limestone, `CaCO_(3)` which on heating gives CaO, It is an exothermic reaction and hence water starts boiling.

Discussion

32.	Which the increase in altitude, the atmopheric pressure
Answer» INCREASES DECREASES remains the some first increases then decreases. Solution :With increase in altitude the atmospheric PRESSURE decreases.

Discussion

33.	Write the symbols of the following elements.(a)Cadmium(b) Bismuth(c )Silicon(d) Argon
Answer» Solution :(a) CADMIUM `to CD` (b)BISMUTH `to BI` (c ) Silicon `to Si` (d)Argon`to AR`

Discussion

34.	Whatis the valence shell ? What is the maximum number of electrons it can have in an atom?
Answer» SOLUTION :The OUTERMOST shell is called valence shell and it can never have more than 8 ELECTRONS in any ATOM.

Discussion

35.	Which among the following pairs of substances has strongest intermolecular forces of attraction ?
Answer» Bromine, mercury Gallium, bromine Bromine, sodium CARBON, POTASSIUM Solution :Carbon and potassium are SOLID substance and hance the intermolecular forces of ATTRACTION among their constituent molecules are the STRONGEST.

Discussion

36.	Which of the following metals cannot be used in printed circuit boards ?
Answer» Copper Aluminium Silver Zinc Solution :Zinc is BRITTLE and hence cannot be USED in printed circuit BOARDS.

Discussion

37.	When Rita opened the perfume bottle in the bedroom without the permission of her mother, how did her mother came to know while watching TV in the drawing room ?
Answer» Solution :Gas particles move with high speeds and the INTERMOLECULAR spaces in gases are very large. These properties of gases allow a gas to diffuse easily into another. As a result, the SMELL of perfume which is in vapour STATE reaces QUICKLY to the other corner of the ROOM.

Discussion

38.	When the water gets converted to ice, its volume
Answer» decrease increases REMAINS the same initially decreases and then increases Solution :When the WATER gets converted to ice, its volume increases as MASS of substance remains same. As a result, DENSITY of ice is less than that of water.

Discussion

39.	Two non-metallic oxides A and B are produced by burning of fossil fuels. A pollutes both air and water. B does not cause water pollution and its presence in water is essential. It causes air pollution. Identify 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

40.	Which among the following is an antacid pair?
Answer» `Mg(OH)_(2), NAOH` `Mg(OH)_(2), A1(OH)_(3)` KOH, NaOH `A1(OH)_(3), NaOH` Solution :ANTACID is the SUBSTANCE which is used to neutralize the acidity in stomach. Generally, ANTACIDS used are MAGNESIUM hydroxide and aluminium hydroxide.

Discussion

41.	Why are people advised not to sleep in a compound Z. 'Z' which is used for construction of monuments gets affected by acid rain. The compound X is used in while washing. Identify X, Y and Z and and write the corresponding balanced chemical equations.
Answer» Solution :It is DANGEROUS to sleep in closed room with COKE burning in improperly desi9gned CHULHA's because coalundergoes incomplete combustion and PRODUCES and produces carbon monoxide which is a harmful GAS and leads to respiratory problems.

Discussion

42.	Which of the following pairs is a major contributor to global warming ?
Answer» Carbon DIOXIDE, oxides of nitrogen Methane, WATER vapour Carbon dioxide, ozone Carbon dioxide, water vapour Solution :`CO_(2)` and watervapour are given house gases PRESENT in atmosphere. Their PERCENTAGE increase in atmosphere increases the temperature of the contributes to GLOBAL warming. These are the major contributors to global warming.

Discussion

43.	Which among the following pairs of bases does not decompose on heating?
Answer» Calcium HYDROXIDE, potassium hydroxide SODIUM hydroxide, potassium hydroxide Copper hydroxide, calcium hydroxide Sodium hydroxide, copper hydroxide Solution :Sodium hydroxide and potassium hydroxide do not DECOMPOSE on heating.

Discussion

44.	The temperature at which solid changes to liquid is called _________
Answer» MELTING POINT boiling point evaporation condensation Solution :The TEMPERATURE at which solid CONVERTS in to liquid is called melting point

Discussion

45.	The solvent water is used in the car radiators. Which of the following properties of water is exploited?
Answer» HIGH solubility Poor conductivity Maximum density High SPECIFIC heat Solution :Water has high specific heat, which means that water needs a LARGE AMOUNT of heat to become hot.

Discussion

46.	Which among the following pairs possess low melting points ?
Answer» MEGNESIUM, mercury Mercury, manganese Sodium, potassium Calcium. Manganese Solution :Sodium and potassium have LOW melting are BOILING POINTS.

Discussion

47.	Y is obtaned by the decomposition of a substance X. Oxygen present in. Y reacts with a neutral oxide and evolves Z which is composed of reddish brown fumes which turns moist blue litmus red. Identify X, Y and Z.
Answer» `H_(2)O_(2),H_(2)" and "CO_(2)` `H_(2)O_(2),O_(2)" and "NO_(2)` `KCIO_(3),CI_(2)" and "O_(2)` `HgO, O_(2)" and "NO` Solution :`underset((X))(H_(2))O_(2)toH_(2)O_(2)+underset((Y))(O_(2))` `NO+underset((Y))(O_(2))tounderset(("reddish brown"))underset((Z))(NO_(2))` `O_(2)` (Y) is neutral towards litmus whlile `NO_(2)` is acidic and HENCE turns moist BLUE to RED.

Discussion

48.	Which of the following is the application of the highest specific heat capacity of water?
Answer» Cooling of SOFTDRINK BOTTLES in ice Cooling of earth's atmosphere after hail storm Usage of water as coolant Bursting of water pipes during WINTER in COLD countries Solution :Water can be used as coolant because of its high specific HEAT.

Discussion

49.	What is meant by neutralisation? Give balanced equations showing neutralisation reactions of the following. (a) Slaked lime and sulphuric acid (b) Sodium bicarbonate and hydrochloric acid. (c) Magnesium carbonate and sulpuric acid.
Answer» Solution :All acids react with alkalies to form SALT and water. The reaction of an acid with a base to form salt and water as the products is called NEUTRALIZATION. (i) `Ca(OH)_(2) + H_(2)SO_(4) rarr CaSO_(4) + 2H_(2)O` (ii) `NaHCO_(3) + HC1 rarr NaC1 + CO_(2) + H_(2)O` (iii) `MgCO_(3) + H_(2)SO_(4) rarr MgSO_(4) + CO_(2) + H_(2)O`

Discussion

50.	What is carbogen ?
Answer» SOLUTION :A mixture of 95% oxygen and 50% `CO_(2)` is called CARBOGEN.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

What is meant by synthesis reaction ? Given an example.

What is the latent heat of fusion and latent heat of vapourization of 10 g of ice and water resepectively?

Which of the following food items provides the maximum energy ?

Which of the following chemical change is a photolytic decomposition reaction?

Though fat provides the maximum amount of energy, it forms a minor part ofour diet while a large part of diet contains carbohydrates?

Which among the following is used to remove moisture from the surroundings?

Which among the following pairs of elements forms cation and anion respectively ?

Which among the following is a detergent?

Which of the following is not a chemical change?

What is the latent heat of fusion and latent heat of vapourisation of 10 g of ice and water respectively?

What is meant by thermal decomposition ? Give an example.

What is depletion of water table?

What is the difference between element and compounds ?

What is the action of litmus on oxygen ?

What are the different kinds of soap? What are the raw materials used for the manufacure of different kinds of soap? Mention their applications.

The salts of which among the pairs of metals cause greater water pollution?

What is meant by rain water harvesting?

What is diffusion ? Give one application.

Y' is obtained by the decomposition of a substance 'X'. Oxygen present in 'X' is univalent. 'Y' reacts with a neuteral oxide and evolves 'Z' which is composed of reddish brown fumes which turns moist blue litmus red. Identify 'X', 'Y' and 'Z'.

Which of thefollowing fertilizers replenishes only one essential among nitrogen, phosphorus

What are fertilizers? How are they classified ? Explain the classification of fertilizers with an example.

Which among the following metals is the most suitable to be used as telecommunication cable?

Whichof thefollowing steps is not involved in the preparation of sodium chloride from sea water ?

Which of the following chemicals leads to water pollution?

Which of the following pair is a major contributor to global warming ?

Which of the following elements is used for the purification of surface water to make it free from germs so that it can be used for drinking purpose?

What do youmean bygrouting? Where does this technique find application ?

Which of the following types of water does not contain dissolved gases such as oxygen and carbon dioxide?

Which of the following water does not contain dissolved gases such as oxygen and carbon dioxide?

Two salts "X" and "Y" are taken in two test tubes "A" and "B" respectively and subjected to heating Water is added to two test tubes, in case of "A" salt regains its original colour and in case of "B" water starts boiling. Then X and Y may be respectively

Which the increase in altitude, the atmopheric pressure

Write the symbols of the following elements.(a)Cadmium(b) Bismuth(c )Silicon(d) Argon

Whatis the valence shell ? What is the maximum number of electrons it can have in an atom?

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

Which of the following metals cannot be used in printed circuit boards ?

When Rita opened the perfume bottle in the bedroom without the permission of her mother, how did her mother came to know while watching TV in the drawing room ?

When the water gets converted to ice, its volume

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

Which among the following is an antacid pair?

Why are people advised not to sleep in a compound Z. 'Z' which is used for construction of monuments gets affected by acid rain. The compound X is used in while washing. Identify X, Y and Z and and write the corresponding balanced chemical equations.

Which of the following pairs is a major contributor to global warming ?

Which among the following pairs of bases does not decompose on heating?

The temperature at which solid changes to liquid is called _________

The solvent water is used in the car radiators. Which of the following properties of water is exploited?

Which among the following pairs possess low melting points ?

Y is obtaned by the decomposition of a substance X. Oxygen present in. Y reacts with a neutral oxide and evolves Z which is composed of reddish brown fumes which turns moist blue litmus red. Identify X, Y and Z.

Which of the following is the application of the highest specific heat capacity of water?

What is meant by neutralisation? Give balanced equations showing neutralisation reactions of the following. (a) Slaked lime and sulphuric acid (b) Sodium bicarbonate and hydrochloric acid. (c) Magnesium carbonate and sulpuric acid.

What is carbogen ?