125876 + Interview Questions in General QA

1.	“Smoke coming out of coal fired chimney appears blue on a misty day.” Why?
Answer» 1. On a misty day, the air has large amount of tiny particles of water droplets, dust and smoke. 2. These tiny particles present in the air scatter blue colour of the white light passing through it. 3. When this scattered blue light reaches our eyes the smoke appears blue.

1.

“Smoke coming out of coal fired chimney appears blue on a misty day.” Why?

Answer»

1. On a misty day, the air has large amount of tiny particles of water droplets, dust and smoke.

2. These tiny particles present in the air scatter blue colour of the white light passing through it.

3. When this scattered blue light reaches our eyes the smoke appears blue.

Discussion

2.	If you are a traffic officer, which steps would you like to suggest to the students to reach the school safely?
Answer» 1. I would create indepth awareness about the rules to be followed on road. 2. Ask the school staff to conduct a mock road usage like Kerb drill. 3. I will ask the students to follow the basic rules like a) Always walk on footpath. b) Cross the road at Zebra Crossing only. c) If Zebra Cross is not available, find safe place to cross, look first at right, then left, if everything is clear – cross the road safety. d) Start early to reach your destination in time and avoid hurriedness on road. e) Follow the traffic signs strictly. Use hand signs wherever necessary. f) Give adequate space to heavy vehicles and never overtake them.

2.

If you are a traffic officer, which steps would you like to suggest to the students to reach the school safely?

Answer»

1. I would create indepth awareness about the rules to be followed on road.

2. Ask the school staff to conduct a mock road usage like Kerb drill.

3. I will ask the students to follow the basic rules like

a) Always walk on footpath.

b) Cross the road at Zebra Crossing only.

c) If Zebra Cross is not available, find safe place to cross, look first at right, then left, if everything is clear – cross the road safety.

d) Start early to reach your destination in time and avoid hurriedness on road.

e) Follow the traffic signs strictly.

Use hand signs wherever necessary.

f) Give adequate space to heavy vehicles and never overtake them.

Discussion

3.	Mention the effects of exchange depreciation on exports
Answer» The currency/exchange depreciation leads to an increase in exports.

Discussion

4.	What is the foreign exchange?
Answer» Foreign exchange refers to all currencies other than the domestic currency of a given country.

Discussion

5.	……. is an electronic device that manipulates information or data according to the set of instructions called program.
Answer» Computer is an electronic device that manipulates information or data according to the set of instructions called program.

Discussion

6.	How will you copy files and folders in windows?
Answer» There are variety of ways to copy files and folders: Method I: COPY and PASTE: To copy a file or folder, first select the file or folder and then choose one of the following: 1. Click Edit → Copy or Ctrl + C or right click → Copy from the pop-up menu. 2. To paste the file(s) or folder(s) in the new location, navigate to the target location then do one of the following: 3. Click Edit → Paste or Ctrl + V. 4. Or Right click → Paste from the pop-up menu. Method II: Drag and Drop: 1. In the RIGHT pane, select the file or folder you want to copy. 2. Click and drag the selected file and/cr folder to the folder list on the left, and drop it where you want to copy the file and/or folder. 3. Your file(s) and folder(s) will now appear in the new area.

6.

How will you copy files and folders in windows?

Answer»

There are variety of ways to copy files and folders:

Method I:

COPY and PASTE:

To copy a file or folder, first select the file or folder and then choose one of the following:

1. Click Edit → Copy or Ctrl + C or right click → Copy from the pop-up menu.

2. To paste the file(s) or folder(s) in the new location, navigate to the target location then do one of the following:

3. Click Edit → Paste or Ctrl + V.

4. Or Right click → Paste from the pop-up menu.

Method II:

Drag and Drop:

1. In the RIGHT pane, select the file or folder you want to copy.

2. Click and drag the selected file and/cr folder to the folder list on the left, and drop it where you want to copy the file and/or folder.

3. Your file(s) and folder(s) will now appear in the new area.

Discussion

7.	Are drives such as hard drive and floppy drives represented with drive letters? If so why, if not why?
Answer» The drive letters plays an important role in telling windows where to look. All the computers with a hard drive will always have that default hard drive assigned to a C: and for floppy drivers has a drive letter of A.

Discussion

8.	Meira Paibi Movement refers to A) prevent pubic disorder due to alcohol abuse B) protect human rights with the massive deployment of Indian armed forces in ManipurC) patrolling the streets at night D) all the above
Answer» D) all the above

Discussion

9.	A solid rectangular piece of iron measures 1.05 m x 70 cm x 1.5 cm. Find the weight of this piece in kilograms if 1 cm3 of iron weighs 8 grams.
Answer» We know that, 1m = 100 cm Therefore, Dimensions of the iron piece will be: 105 cm × 70 cm × 1.5 cm We know that, Volume of cuboid = Length × Breadth × Height Total volume of the piece of iron = 105 × 70 × 1.5 = 11025 cm³ We also know that, 1 cm³ = 8 gms Therefore, Weight of the piece = 11025 × 8 = 88200 g = \(\frac{88200}{1000}\) = 88.2 kg

9.

A solid rectangular piece of iron measures 1.05 m x 70 cm x 1.5 cm. Find the weight of this piece in kilograms if 1 cm3 of iron weighs 8 grams.

Answer»

We know that,

1m = 100 cm

Therefore,

Dimensions of the iron piece will be: 105 cm × 70 cm × 1.5 cm

We know that,

Volume of cuboid = Length × Breadth × Height

Total volume of the piece of iron = 105 × 70 × 1.5

= 11025 cm³

We also know that,

1 cm³ = 8 gms

Therefore,

Weight of the piece = 11025 × 8 = 88200 g

= \(\frac{88200}{1000}\)

= 88.2 kg

Discussion

10.	The area of a courtyard is 3750 m2. Find the cost of covering it with gravel to a height of 1 cm if the gravel costs Rs. 6.40 per cubic metre.
Answer» We know that, 1 cm = 0.01m Therefore, Volume of the gravel used = Area × Height = 3750 × 0.01 = 37.5 m³ It is given in the question that cost of the gravel is Rs. 6.40 per cubic meter Therefore, Total cost of covering = (37.5 × 6.4) = Rs. 240

10.

The area of a courtyard is 3750 m2. Find the cost of covering it with gravel to a height of 1 cm if the gravel costs Rs. 6.40 per cubic metre.

Answer»

We know that,

1 cm = 0.01m

Therefore,

Volume of the gravel used = Area × Height

= 3750 × 0.01

= 37.5 m³

It is given in the question that cost of the gravel is Rs. 6.40 per cubic meter

Therefore,

Total cost of covering = (37.5 × 6.4)

= Rs. 240

Discussion

11.

What is the difference between skeletal equation and balanced chemical equation? Give example.

Answer»

The difference between skeletal equation and balanced chemical equation is as follows:

Skeletal Equation	Balanced Equation
1. The number of atoms of each element is not same.	1. The number of atoms of each element is same.
2. These equations are needed to be balanced.	2. These equations are not needed to be balanced.
3. Mass is not same on the both sides of equation.	3. Mass is same on the both sides of equation.
4. E.g. Mg + O₂ → MgO	4. E.g. 3Fe + 4H₂O → Fe₃O₄

Discussion

12.	“We need to balance a skeletal chemical equation.” Give reason to justify this statement.
Answer» Balanced chemical equation: A chemical equation in which the number of atoms of reactants are equal to the number of atoms of products is called a balanced equation. We need to balance a skeletal chemical equation because: i. According to the law of conservation of mass, mass (or atoms) are neither created nor destroyed in chemical reactions. ii. It means the total mass of the products formed in chemical reaction must be equal to the mass of reactants consumed.

12.

“We need to balance a skeletal chemical equation.” Give reason to justify this statement.

Answer»

Balanced chemical equation: A chemical equation in which the number of atoms of reactants are equal to the number of atoms of products is called a balanced equation.

We need to balance a skeletal chemical equation because:

i. According to the law of conservation of mass, mass (or atoms) are neither created nor destroyed in chemical reactions.

ii. It means the total mass of the products formed in chemical reaction must be equal to the mass of reactants consumed.

Discussion

13.	Define variations.
Answer» Variations are differences that occur between the organisms of the same species in spite of the same basic feature.

Discussion

14.	Define heredity.
Answer» Heredity deals with the inheritance of characters from one generation to the next.

Discussion

15.	What were the criteria used by Mendeleev in creating his Periodic Table?
Answer» 1. Mendeleev arranged the elements in the order of their increasing atomic masses. 2. He also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties.

15.

What were the criteria used by Mendeleev in creating his Periodic Table?

Answer»

1. Mendeleev arranged the elements in the order of their increasing atomic masses.

2. He also observed that there occurs a periodic recurrence of elements with similar physical and chemical properties.

Discussion

16.	With whom we associate theory of evolution? (a) Charles Darwin (b) Mendel (c) Stanley Miller (d) Harold Urey
Answer» (a) Charles Darwin

Discussion

17.	If we breed a group of squirrels and surgically remove their tails, then amongst the progeny of these tailless squirrels– (a) All have no tail (b) All have a tail (c) Some of them have tails (d) Cannot be determined.
Answer» (b) All have a tail

Discussion

18.	What is Endocrine glands?
Answer» Different types of endocrine glands present in our body are the pituitary gland, the pineal gland, the hypothalamus, the thyroid, the parathyroid, the thymus, the adrenal gland, the pancreas, the testes and the ovary.

Discussion

19.	Refer to the given figure. lt shows bones of wings of two animals X and Y. These wings are Z structures. Select the option that correctly identifies X, Y and Z.
Answer» Correct option (A) Explanation: Analogous organs (structures) are those organs which have similar functions but are different in their structural details and origin. Wings of bat and bird are analogous organs. Wings of bats are skin folds stretched mainly between elongated fingers, but the wings of a bird are feathery covering all along the arm. The basic designs of the wings of bat and the bird, their structure and components are very different. They only look similar because both are adapted for flying but their origins are different.

19.

Refer to the given figure. lt shows bones of wings of two animals X and Y. These wings are Z structures. Select the option that correctly identifies X, Y and Z.

Answer»

Correct option (A)

Explanation:

Analogous organs (structures) are those organs which have similar functions but are different in their structural details and origin. Wings of bat and bird are analogous organs. Wings of bats are skin folds stretched mainly between elongated fingers, but the wings of a bird are feathery covering all along the arm. The basic designs of the wings of bat and the bird, their structure and components are very different. They only look similar because both are adapted for flying but their origins are different.

Discussion

20.	Explain The adrenal glands.
Answer» These are located above the kidneys. Two regions of the adrenal gland are adrenal cortex and adrenal medulla. • Adrenal cortex secretes the hormones like cortisol, aldosterone and androgens. • Adrenal medulla secretes the hormones like adrenaline and noradrenaline. Adrenaline is also called the “hormone of fight or flight,” or the emergency hormone. It prepares the body to face an emergency condition of physical stress, like danger, anger and excitement.

20.

Explain The adrenal glands.

Answer»

These are located above the kidneys.

Two regions of the adrenal gland are adrenal cortex and adrenal medulla.

• Adrenal cortex secretes the hormones like cortisol, aldosterone and androgens.

• Adrenal medulla secretes the hormones like adrenaline and noradrenaline. Adrenaline is also called the “hormone of fight or flight,” or the emergency hormone. It prepares the body to face an emergency condition of physical stress, like danger, anger and excitement.

Discussion

21.	Explain The thyroid gland.
Answer» • It is located in the neck, ventral to the larynx. • It is the one of the largest endocrine glands. • The principal hormones produced by this gland are triiodothyronine and thyroxine. • Thyroxine is a hormone that regulates the metabolism of carbohydrates, proteins and fats in the body. Iodine is essential for the synthesis of thyroxin. Deficiency of iodine in food causes goiter. One of the symptoms in this disease is a swollen neck.

21.

Explain The thyroid gland.

Answer»

• It is located in the neck, ventral to the larynx.

• It is the one of the largest endocrine glands.

• The principal hormones produced by this gland are triiodothyronine and thyroxine.

• Thyroxine is a hormone that regulates the metabolism of carbohydrates, proteins and fats in the body. Iodine is essential for the synthesis of thyroxin. Deficiency of iodine in food causes goiter. One of the symptoms in this disease is a swollen neck.

Discussion

22.	Mendel selected garden peas as his experimental material because (i) Pea plants possess a number of well defined contrasting characters. (ii) Pea plants contain unisexual flowers. (iii) Pea plants have perfect bisexual flowers.(iv) These are annual plants. (A) (i) and (iv) only (B) (i) and (ii) only (C) (i) and (iii) only (D) (i), (iii) and (iv) only
Answer» (D) (i), (iii) and (iv) only

Discussion

23.	If A and B have n characteristics common while A and C have n/2 characteristics common, then which of the two organisms are more closely related? (a) A and C (b) A and B (c) Characteristics need to be known (d) None of these
Answer» (c) Characteristics need to be known

Discussion

24.	Forelimbs of organisms X and Y are.......organs while forelimbs of organisms Y and Z are .....organs Direction: Read the given passage and answer the following questions. Siddhi studied forelimbs of three organisms and described them as follows : Organism X - Long and short bones, covered with muscles, used for running. Organism Y - Long and short bones, covered with feathers used for flying. Organism Z - A layer of a complex chemical with supporting framework which is not made of bones and used for flying.(A) Analogous, Vestigial (B) Homologous, Vestigial (C) Analogous, Homologous (D) Homologous, Analogous
Answer» Correct option (D) Homologous, Analogous Explanation: Organisms X and Y are vertebrates. X is a mammal whereas Y is a bird. Z is an insect (invertebrate). Forelimbs of vertebrates are homologous organs, i.e., organs having same fundamental structure but performs different functions. Wings of insects and wings of birds are analogous organs, i.e., organs having similar functions but different in their structural details and origin.

24.

Forelimbs of organisms X and Y are.......organs while forelimbs of organisms Y and Z are .....organs Direction: Read the given passage and answer the following questions. Siddhi studied forelimbs of three organisms and described them as follows : Organism X - Long and short bones, covered with muscles, used for running. Organism Y - Long and short bones, covered with feathers used for flying. Organism Z - A layer of a complex chemical with supporting framework which is not made of bones and used for flying.(A) Analogous, Vestigial (B) Homologous, Vestigial (C) Analogous, Homologous (D) Homologous, Analogous

Answer»

Correct option (D) Homologous, Analogous

Explanation:

Organisms X and Y are vertebrates. X is a mammal whereas Y is a bird. Z is an insect (invertebrate). Forelimbs of vertebrates are homologous organs, i.e., organs having same fundamental structure but performs different functions. Wings of insects and wings of birds are analogous organs, i.e., organs having similar functions but different in their structural details and origin.

Discussion

25.	ln which of the following organisms sex determination occurs under the effect of environmental factors? (A) Chrysemys picta (B) Homo sapiens (C) Drosophila melanogaster (D) Pavo cristatus
Answer» Correct option (A) Chrysemys picta Explanation: ln Chrysemys picta, a species of turtle, high incubation temperature above 33°C results in development of female progeny while a temperature below 28°C produces only males. lt is an example of effect of environmental role on sex determination.

25.

ln which of the following organisms sex determination occurs under the effect of environmental factors? (A) Chrysemys picta (B) Homo sapiens (C) Drosophila melanogaster (D) Pavo cristatus

Answer»

Correct option (A) Chrysemys picta

Explanation:

ln Chrysemys picta, a species of turtle, high incubation temperature above 33°C results in development of female progeny while a temperature below 28°C produces only males. lt is an example of effect of environmental role on sex determination.

Discussion

26.	Explain Sex determination.
Answer» It is a mechanism which determines the individual to be a male or a female based on the sex chromosomes present in it. In human beings, sex is determined by genetic inheritance. Genes inherited from the parents determine whether an offspring will be a boy or a girl. Gene for all the characters are linearly arrange on the chromosomes. The chromosomes that carry genes for sexual characters are called autosomes or sex chromosomes while those that carry genes for the vegetative characters are called autosomes or non sex chromosomes. Women have XX chromosomes while men have XY. All the children will inherit an X chromosome from their mother regardless of whether they are boys or girls. Thus the sex of the children will be determined by what they inherit from their father.

26.

Explain Sex determination.

Answer»

It is a mechanism which determines the individual to be a male or a female based on the sex chromosomes present in it. In human beings, sex is determined by genetic inheritance. Genes inherited from the parents determine whether an offspring will be a boy or a girl. Gene for all the characters are linearly arrange on the chromosomes. The chromosomes that carry genes for sexual characters are called autosomes or sex chromosomes while those that carry genes for the vegetative characters are called autosomes or non sex chromosomes.

Women have XX chromosomes while men have XY.

All the children will inherit an X chromosome from their mother regardless of whether they are boys or girls. Thus the sex of the children will be determined by what they inherit from their father.

Discussion

27.	The forelimbs of a frog, a bird and a man show the same basic design (or basic structure) of bones. What name is given to such organs ?
Answer» Homologous Organs.

Discussion

28.	Quick lime reacts vigorously with water releasing a large amount of heat. Which type of reaction is this ? 1) Precipitation reaction2) Combination reaction 3) Decomposition reaction 4) Exothermic reaction A) 1, 2 B) 2, 3 C) 2, 4 D) 4
Answer» Correct option is C) 2, 4

Discussion

29.	What is the Dalton’s atomic theory?
Answer» Dalton’s Atomic theory- All matter is made of atoms. Atoms are indivisible and indestructible. All atoms of a given element are identical in mass and properties. Compounds are formed by a combination of two or more different kinds of atoms. A chemical reaction is a rearrangement of atoms.

29.

What is the Dalton’s atomic theory?

Answer»

Dalton’s Atomic theory-

All matter is made of atoms. Atoms are indivisible and indestructible.
All atoms of a given element are identical in mass and properties.
Compounds are formed by a combination of two or more different kinds of atoms.
A chemical reaction is a rearrangement of atoms.

Discussion

30.	The process of preparing slaked lime by adding water to quicklime is this type of chemical reaction. A) Decomposition reaction B) Exothermic reaction C) Endothermic reaction D) Displacement reaction
Answer» B) Exothermic reaction

Discussion

31.	Why does Venus twinkle like a star?
Answer» Venus reaches inferior conjunction today, officially leaving the evening sky. It has been low in the sky, where Earth's atmosphere has caused Venus to scintillate, or twinkle, in many colors. Planets usually shine steadily. But bright Venus is twinkling now – shining in multiple colors – because it's so low in the sky.

Discussion

32.	Balance the chemical equationsBaCl2 + H2SO4 ➝ BaSO4 + HCl
Answer» BaCl₂ + H₂SO₄ ➝ BaSO₄ + 2HCl

Discussion

33.

Enumerate the common defects of vision, their causes and the possible methods of correcting them.

Answer»

Defect of vision	Cause	Corrective measure
Myopia	Lengthening of eye ball from front to back or the lens is too curved.	Using suitable concave lens
Hyperopia	Shortening of eye ball from front to back or the lens is too flat.	Using suitable convex lens
Astigmatism	Uneven curvature of the cornea	Using suitable cylindrical lenses
Presbyopia	Loss of flexibility of lens	Using suitable convex lens
Cataract	Lens turning opaque	Surgery or use of convex lens or implantation of plastic lens.
Colour blindness	Genetic defect	No control measure
Squint	Formation of cross-eye	Surgery and suitable exercise

Discussion

34.	How can corrosion be prevented?
Answer» 1. Corrosion damages buildings, bridges, automobiles, ships, iron railings and other articles made of iron. 2. It can be prevented by using an anti-rust solution, coating the surface by a paint, processes like galvanising and electroplating with other metals.

34.

How can corrosion be prevented?

Answer»

1. Corrosion damages buildings, bridges, automobiles, ships, iron railings and other articles made of iron.

2. It can be prevented by using an anti-rust solution, coating the surface by a paint, processes like galvanising and electroplating with other metals.

Discussion

35.	How are compounds formed?
Answer» Compounds are formed by a chemical combination of two or more different kinds of atoms.

Discussion

36.	Why can stars be seen without planets?
Answer» The planets are much closer, inside our solar system. Although the planets are much smaller than the stars, planets appear to be about the same size as the stars because they are so close to us. Planets don't produce their own light. They reflect the light of the sun in the same way our moon reflects sunlight.

Discussion

37.	What are the molecular formulae of salt, slaked lime, water, lime, limestone?
Answer» The molecular formulae for Salt – Sodium chloride – NaCl Slaked lime – Calcium hydroxide Ca(OH)₂ Water – H₂O Lime – Calcium oxide – CaO Lime stone – Calcium carbonate – CaCO₃

37.

What are the molecular formulae of salt, slaked lime, water, lime, limestone?

Answer»

The molecular formulae for

Salt – Sodium chloride – NaCl

Slaked lime – Calcium hydroxide Ca(OH)₂

Water – H₂O

Lime – Calcium oxide – CaO

Lime stone – Calcium carbonate – CaCO₃

Discussion

38.	Millions of people of the developing countries of world are suffering from corneal blindness. These persons can be cured by replacing the defective cornea with the cornea of a donated eye. A charitable society of your city has organised a campaign in your neighbourhood in order to create awareness about this fact. If you ate asked to participate in this mission how would you contribute in this noble cause ? (i) State the objective of organising such campaigns. (ii) List two arguments which you would give to motivate the people to donate their eyes after death. (iii) List two values which are developed in the persons who actively participate and contribute in such programmes.
Answer» (i) Objectives - To make people aware and realize their duties towards society. (ii) One person can give sight to two people. Our eyes can live even after our death. (iii) Concern for others/ Responsible behavior/ Group work or any other.

38.

Millions of people of the developing countries of world are suffering from corneal blindness. These persons can be cured by replacing the defective cornea with the cornea of a donated eye. A charitable society of your city has organised a campaign in your neighbourhood in order to create awareness about this fact. If you ate asked to participate in this mission how would you contribute in this noble cause ? (i) State the objective of organising such campaigns. (ii) List two arguments which you would give to motivate the people to donate their eyes after death. (iii) List two values which are developed in the persons who actively participate and contribute in such programmes.

Answer»

(i) Objectives - To make people aware and realize their duties towards society.

(ii) One person can give sight to two people. Our eyes can live even after our death.

(iii) Concern for others/ Responsible behavior/ Group work or any other.

Discussion

39.	Two samples ‘m’ and ‘n’ of slaked lime were obtained from two different reactions. The details about their composition are as follows:‘sample m’ mass : 7g Mass of constituent oxygen : 2g Mass of constituent calcium : 5g ‘sample n’ mass : 1.4g Mass of constituent oxygen : 0.4g Mass of constituent calcium : 1.0g(1) Which law of chemical combination does this prove? Explain.
Answer» (i) The expected proportion by weight of the constituent elements of quick lime that is calcium oxide would be from its known molecular formula CaO. The atomic mass of Ca and O are 40 and 16 respectively. This means, the proportion by weight of the constituent elements Ca and O in the compound CaO is 40 :16 which is 5 : 2. (ii) Now, for the given sample’m’ of CaO = 5 g mass of given sample = 7 g mass of constituent Ca in sample’m’ = 5 g mass of constituent O in sample’m’ = 2 g (iii) This means that 7 g of calcium oxide contairis 5 g of calcium (Ca) and 2 g of oxygen (O); apd the proportion by weight of calcium and oxygen in it is 5 : 2. (iv) Now, for the given sample ‘n’ of CaO mass of given sample CaO = 1.4 g Mass of constituent Ca in sample ‘n’ = 1.0 g Mass of constituent O in sample ‘n’ = 0.4 g This means that 1.4g of calcium oxide contains 1.0 g of calcium (Ca) and 0.4 g of oxygen (O); and the proportion by weight of calcium and oxygen in it is 5 : 2. (v) Above samples’m’ and ‘n’ of calcium oxide (CaO) shows that the proportion by weight of the constituent elements in different samples of a compound is always constant that is the proportion by weight of calcium (Ca) and oxygen (O) in different samples of calcium oxide (CaO) is constant. (vi) The experimental value of proportion by weight of the constituent elements matched with the expected proportion calculated by molecular mass. This proves and verifies the law of constant proportion. The law states that ‘The proportion by weight of the constituent elements in the various samples of a compound is fixed’.

39.

Two samples ‘m’ and ‘n’ of slaked lime were obtained from two different reactions. The details about their composition are as follows:‘sample m’ mass : 7g Mass of constituent oxygen : 2g Mass of constituent calcium : 5g ‘sample n’ mass : 1.4g Mass of constituent oxygen : 0.4g Mass of constituent calcium : 1.0g(1) Which law of chemical combination does this prove? Explain.

Answer»

(i) The expected proportion by weight of the constituent elements of quick lime that is calcium oxide would be from its known molecular formula CaO. The atomic mass of Ca and O are 40 and 16 respectively. This means, the proportion by weight of the constituent elements Ca and O in the compound CaO is 40 :16 which is 5 : 2.

(ii) Now, for the given sample’m’ of CaO = 5 g

mass of given sample = 7 g

mass of constituent Ca in sample’m’ = 5 g

mass of constituent O in sample’m’ = 2 g

(iii) This means that 7 g of calcium oxide contairis 5 g of calcium (Ca) and 2 g of oxygen (O); apd the proportion by weight of calcium and oxygen in it is 5 : 2.

(iv) Now, for the given sample ‘n’ of CaO mass of given sample CaO = 1.4 g

Mass of constituent Ca in sample ‘n’ = 1.0 g

Mass of constituent O in sample ‘n’ = 0.4 g

This means that 1.4g of calcium oxide contains 1.0 g of calcium (Ca) and 0.4 g of oxygen (O); and the

proportion by weight of calcium and oxygen in it is 5 : 2.

(v) Above samples’m’ and ‘n’ of calcium oxide (CaO) shows that the proportion by weight of the constituent elements in different samples of a compound is always constant that is the proportion by weight of calcium (Ca) and oxygen (O) in different samples of calcium oxide (CaO) is constant.

(vi) The experimental value of proportion by weight of the constituent elements matched with the expected proportion calculated by molecular mass. This proves and verifies the law of constant proportion.

The law states that ‘The proportion by weight of the constituent elements in the various samples of a compound is fixed’.

Discussion

40.	Zinc reacts with hydrochloric acid. The reaction is a reaction. (a) combination (b) decomposition (c) displacement (d) double decomposition
Answer» Correct option is: (c) displacement c... displacement Zn + 2HCL - ZnCl₂+ h₂

Discussion

41.

41.	Magnesium reacts with con. HCl to form………..salt. (a) copper chloride (b) ferrous chloride (c) calcium chloride (d) magnesium chloride
Answer» Correct option is: (d) magnesium chloride `Mg + 2HCL -> MgCl` ₂+ h₂ `_\|` `_magnesium` `_chloride`

Magnesium reacts with con. HCl to form………..salt. (a) copper chloride (b) ferrous chloride (c) calcium chloride (d) magnesium chloride

Answer»

Correct option is: (d) magnesium chloride

Mg + 2HCL -> MgCl

₂+ h₂

_|

_magnesium

_chloride

Discussion

42.	State whether the following statements are True or False:i. Nascent oxygen is always denoted by showing the symbol of oxygen.ii. Antioxidants are used to prevent oxidation or food containing fats and oils.iii. When oils and fats are allowed to stand for a long time, they become rancid.iv. The chemical formula of rust is Fe3O4 xH2O.v. Glucose combines with oxygen in our body and provides energy. The reaction is an endothermic reaction.
Answer» i. False. (Nascent oxygen is always denoted by showing symbol of oxygen (0) in square brackets.) ii. True. iii. True. iv. False. (The chemical formula or rust is Fe₂O₃ xH₂O.) v. False. (Glucose combines with oxygen in our body and provides energy. The reaction is an exothermic reaction.)

42.

State whether the following statements are True or False:i. Nascent oxygen is always denoted by showing the symbol of oxygen.ii. Antioxidants are used to prevent oxidation or food containing fats and oils.iii. When oils and fats are allowed to stand for a long time, they become rancid.iv. The chemical formula of rust is Fe3O4 xH2O.v. Glucose combines with oxygen in our body and provides energy. The reaction is an endothermic reaction.

Answer»

i. False. (Nascent oxygen is always denoted by showing symbol of oxygen (0) in square brackets.)

ii. True.

iii. True.

iv. False. (The chemical formula or rust is Fe₂O₃ xH₂O.)

v. False. (Glucose combines with oxygen in our body and provides energy. The reaction is an exothermic reaction.)

Discussion

43.	Write true or false for the following statements:Iron shows valency of Fe2+ and Fe3+.
Answer» True Iron shows variable valency. It shows valency of Fe²⁺ and Fe³⁺simultaneously. For example: In ferrous oxide: Fe²⁺ and in ferric oxide: Fe³⁺ Hence, the given statement is true.

43.

Write true or false for the following statements:Iron shows valency of Fe2+ and Fe3+.

Answer»

True

Iron shows variable valency. It shows valency of Fe²⁺ and Fe³⁺simultaneously.

For example: In ferrous oxide: Fe²⁺ and in ferric oxide: Fe³⁺

Hence, the given statement is true.

Discussion

44.	While performing an experiment a student observes that when he heats some green crystals in a boiling tube, the colour of the crystals changes to brown and a gas evolves which smells like burning sulphur. Interpret the observations and results.
Answer» Observation: The green colour of ferrous sulphate crystals changes to brownish black ferric oxide and smell of burning sulphur is observed. Result: Heating of ferrous sulphate is a thermal decomposition reaction because of ferrous sulphate breaks down into simpler compounds-Fe₂O₃, SO₂ and SO₃. 2FeSO₄(s) +Heat → Fe₂O₃(s) + SO₂(g) + SO₃(g)

44.

While performing an experiment a student observes that when he heats some green crystals in a boiling tube, the colour of the crystals changes to brown and a gas evolves which smells like burning sulphur. Interpret the observations and results.

Answer»

Observation: The green colour of ferrous sulphate crystals changes to brownish black ferric oxide and smell of burning sulphur is observed.

Result: Heating of ferrous sulphate is a thermal decomposition reaction because of ferrous sulphate breaks down into simpler compounds-Fe₂O₃, SO₂ and SO₃.

2FeSO₄(s) +Heat → Fe₂O₃(s) + SO₂(g) + SO₃(g)

Discussion

45.	In a double displacement reaction,…………(a) ions remain at rest (b) ions get liberated (c) ions are exchanged (d) ions are not created
Answer» Correct option is: (c) ions are exchanged c. ions are exchanged

Discussion

46.	Identify the chemical change :Melting of Ice or Conversion of milk into curd.
Answer» Chemical Change is : Conversion of milk into curd.

Discussion

47.	Observe the following figures A and B.State the change in substances taken is test-tubes A and B. Mention the type of reaction in each case.
Answer» ln A. green colour of solution fades away and brown-red deposition on iron nail occurs displacement reaction. In B, a reddish brown substance is left in the test tube- decomposition reaction

Discussion

48.	State whether the following statements are True or False:i. Rusting of iron is a fast reaction.ii. Milk is set into curd is a chemical change.iii. The reaction between salt and water is an example of exothermic reaction.iv. The speed of a chemical reaction depends on the catalyst used in the chemical reaction.v. The simple form of representation of a chemical reaction in words is known as word reaction.
Answer» i. False. (Rusting of iron is a slow reaction.) ii. True. iii. False. (The reaction between salt and water is an example of endothermic reaction.) iv. True. v. True.

48.

State whether the following statements are True or False:i. Rusting of iron is a fast reaction.ii. Milk is set into curd is a chemical change.iii. The reaction between salt and water is an example of exothermic reaction.iv. The speed of a chemical reaction depends on the catalyst used in the chemical reaction.v. The simple form of representation of a chemical reaction in words is known as word reaction.

Answer»

i. False. (Rusting of iron is a slow reaction.)

ii. True.

iii. False. (The reaction between salt and water is an example of endothermic reaction.)

iv. True.

v. True.

Discussion

49.

Rupali, a class 10 student has set up the apparatus as shown in the figures.Which of the following observations is correct?(A) Temperature of beakers l, ll and lll will be raised as dissolution of salts is an exothermic process. (B) Temperature of beakers lll and lV will be raised while temperature of beakers I and ll will fall. (C) Temperature will rise only in beaker lV as redox reactions are exothermic. (D) None of these

Answer»

Correct option (B) Temperature of beakers lll and lV will be raised while temperature of beakers I and ll will fall.

Explanation:

Dissolution of salts may be endothermic or exothermic but displacement reactions are always exothermic.

Discussion

50.

Give two examples of fast speed reactions.

Answer»

(1) The reaction between sodium hydroxide (NaOH) and hydrochloric acid (HCl) is a neutralization reaction and it is fast speed reaction.

NaOH_2(aq) + HCl_(aq) → NaCl_(aq) + H₂O_(I)

This neutralizaton reaction is completed in short time, therefore it is fast speed reaction.

(2) Aqueous solution of sodium chloride reacts with silver nitrate solution to form white precipitate of silver chloride (NaCl) and sodium nitrate.

NaCl_(aq) + AgNO_3(aq) → NaNO_3(aq) + AgCl ↓

This reaction is completed in short time, therefore it is fast reaction.

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

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While performing an experiment a student observes that when he heats some green crystals in a boiling tube, the colour of the crystals changes to brown and a gas evolves which smells like burning sulphur. Interpret the observations and results.

In a double displacement reaction,…………(a) ions remain at rest (b) ions get liberated (c) ions are exchanged (d) ions are not created

Identify the chemical change :Melting of Ice or Conversion of milk into curd.

Observe the following figures A and B.State the change in substances taken is test-tubes A and B. Mention the type of reaction in each case.

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