Solved 2022 Term 1 Question Paper CBSE Class 10 Science

Section A

Question 1

A student took Sodium Sulphate solution in a test tube and added Barium Chloride solution to it. He observed that an insoluble substance has formed. The colour and molecular formula of the insoluble substance is:

1. Grey, Ba₂SO₄
2. Yellow, Ba(SO₄)₂
3. White, BaSO₄
4. Pink, BaSO₄

Answer

White, BaSO₄

Reason — When sodium sulphate is reacted with barium chloride, a white ppt. of barium sulphate is produced.

Na₂SO₄ (aq) + BaCl₂ (aq) ⟶ BaSO₄ (s) + 2NaCl (aq)

Question 2

Which of the following oxide(s) is/are soluble in water to form alkalis?

(i) Na₂O

(ii) SO₂

(iii) K₂O

(iv) NO₂

1. (i) and (iii)
2. (i) only
3. (ii) and (iv)
4. (iii) only

Answer

(i) and (iii)

Reason — Sodium oxide and potassium oxide dissolve in water to form alkalis.

Na₂O + H₂O ⟶ 2NaOH

K₂O + H₂O ⟶ 2KOH

Question 3

Study the diagram given below and identify the gas formed in the reaction.

1. Carbon di-oxide which extinguishes the burning candle.
2. Oxygen due to which the candle burns more brightly.
3. Sulphur dioxide which produces a suffocating smell.
4. Hydrogen which while burning produces a popping sound.

Answer

Hydrogen which while burning produces a popping sound.

Reason — When zinc reacts with sulphuric acid, it produces hydrogen gas and zinc sulphate.

Zn + H₂SO₄ ⟶ ZnSO₄ + H₂↑

Question 4

Sodium reacts with water to form sodium hydroxide and hydrogen gas. The balanced equation which represents the above reaction is

1. Na(s) + 2H₂O(l) ⟶ 2NaOH(aq) + 2H₂(g)
2. 2Na(s) + 2H₂O(l) ⟶ 2NaOH(aq) + H₂(g)
3. 2Na(s) + 2H₂O(l) ⟶ NaOH(aq) + 2H₂(g)
4. 2Na(s) + H₂O(l) ⟶ 2NaOH(aq) + 2H₂(g)

Answer

2Na(s) + 2H₂O(l) ⟶ 2NaOH(aq) + H₂(g)

Reason — The balanced equation for the reaction between sodium and water to form sodium hydroxide and hydrogen gas is:

2Na(s) + 2H₂O(l) ⟶ 2NaOH(aq) + H₂(g)

Question 5

Which of the options in the given table are correct?

1. (i) and (ii)
2. (i) and (iv)
3. (ii) and (iii)
4. (iii) and (iv)

Answer

(ii) and (iii)

Reason — Sour milk contains lactic acid and ant sting contains methanoic acid.

Question 6

C₆H₁₂O₆ (aq) + 6O₂ (aq) ⟶ 6CO₂ (aq) + 6H₂O (l)

The above reaction is a/an

1. displacement reaction
2. endothermic reaction
3. exothermic reaction
4. neutralisation reaction

Answer

exothermic reaction

Reason — The name of the above reaction is respiration and it is an exothermic reaction. The glucose from food combines with oxygen in the cells of our body and provides energy as heat.

Question 7

Which of the following statements about the reaction given below are correct?

MnO₂ + 4HCl ⟶ MnCl₂ + 2H₂O + Cl₂

(i) HCl is oxidized to Cl₂

(ii) MnO₂ is reduced to MnCl₂

(iii) MnCl₂ acts as an oxidizing agent

(iv) HCl acts as on oxidizing agent

1. (ii), (iii) and (iv)
2. (i), (ii) and (iii)
3. (i) and (ii) only
4. (iii) and (iv) only

Answer

(i) and (ii) only

Reason — The reaction is a redox reaction where, HCl is oxidized to Cl₂ as it loses hydrogen whereas MnO₂ is reduced to MnCl₂ as it loses oxygen.

Question 8

Select from the following the statement which is true for bases.

1. Bases are bitter and turn blue litmus red.
2. Bases have a pH less than 7.
3. Bases are sour and change red litmus to blue.
4. Bases turn pink when a drop of phenolphthalein is added to them.

Answer

Bases turn pink when a drop of phenolphthalein is added to them.

Reason — Phenolphthalein is a pH indicator which turns pink when added to a basic solution.

Question 9

Study the following table and choose the correct option:

Answer

Reason — Sodium acetate made from acetic acid and sodium hydroxide is basic in nature.

Question 10

It is important to balance the chemical equations to satisfy the law of conservation of mass. Which of the following statements of the law is incorrect?

1. The total mass of the elements present in the reactants is equal to the total mass of the elements present in the products.
2. The number of atoms of each element remains the same, before and after a chemical reaction.
3. The chemical composition of the reactants is the same before and after the reaction.
4. Mass can neither be created nor can it be destroyed in a chemical reaction.

Answer

The chemical composition of the reactants is the same before and after the reaction.

Reason — During the reaction, the chemical composition of the reactants change to form new products. Hence, this statement is incorrect.

Question 11

Consider the following statements in connection with the functions of the blood vessels marked A and B in the diagram of a human heart as shown.

(i) Blood vessel A — It carries carbon dioxide rich blood from the lungs.

(ii) Blood vessel B — It carries oxygen rich blood from the lungs.

(iii) Blood vessel B — Left atrium relaxes as it receives blood from this blood vessel.

(iv) Blood vessel A — Right atrium has thick muscular wall as it has to pump blood to this blood vessel.

The correct statements are

1. (i) and (ii) only
2. (ii) and (iii) only
3. (ii), (iii) and (iv)
4. (i), (ii) and (iii)

Answer

(i), (ii) and (iii)

Reason— Blood vessel A is Pulmonary artery that takes deoxygenated blood to lungs and Blood vessel B is Pulmonary vein that takes oxygenated blood from lungs to left atrium.

Question 12

In living organisms during respiration which of the following products are not formed if oxygen is not available?

1. Carbon dioxide + Water
2. Carbon dioxide + Alcohol
3. Lactic acid + Alcohol
4. Carbon dioxide + Lactic acid

Answer

Carbon dioxide + Water

Reason — Carbon dioxide + Water is formed during aerobic respiration in presence of oxygen.

Question 13

The correct statements with reference to single celled organisms are:

(i) Complex substances are not broken down into simpler substances.

(ii) Simple diffusion is sufficient to meet the requirement of exchange of gases.

(iii) Specialised tissues perform different functions in the organism.

(iv) Entire surface of organism is in contact wih the environment for taking in food.

1. (i) and (iii)
2. (ii) and (iii)
3. (ii) and (iv)
4. (i) and (iv)

Answer

(ii) and (iv)

Reason — In unicellular organisms respiration occurs by simple diffusion and they have entire cell surface to take food.

Question 14

Which one among the following is not removed as a waste product from the body of a plant?

1. Resins and Gums
2. Urea
3. Dry Leaves
4. Excess water

Answer

Urea

Reason — Plants do not excrete urea. Urea is an animal waste product.

Question 15

Which of the following statements are correct in reference to the role of A (shown in the given diagram) during a breathing cycle in human beings?

(i) It helps to decrease the residual volume of the air in lungs.

(ii) It flattens as we inhale.

(iii) It gets raised as we inhale.

(iv) It helps the chest cavity to become larger.

1. (ii) and (iv)
2. (iii) and (iv)
3. (i) and (ii)
4. (i), (ii) and (iv)

Answer

(ii) and (iv)

Reason — While breathing in, we lift our ribs and flatten our diaphragm, and the chest cavity becomes larger. Because of this, air is sucked into the lungs and fills the expanded alveoli.

Question 16

Which one of the following conditions is true for the state of stomata of a green leaf shown in given diagram?

1. Large amount of water flows into the guard cells.
2. Gaseous exchange is occurring in large amount.
3. Large amount of water flows out from the guard cells.
4. Large amount of sugar collects in the guard cells.

Answer

Large amount of water flows out from the guard cells.

Reason — Large amount of water flows out from the guard cells making the cells flaccid. This closes the stomata. The stomata opens again when guard cells become turgid by taking in water.

Question 17

In which of the following is a concave mirror used?

1. A solar cooker
2. A rear view mirror in vehicles.
3. A safety mirror in shopping malls.
4. In viewing full size image of distant tall buildings.

Answer

A solar cooker

Reason — Large concave mirrors are used to concentrate sunlight to produce heat in solar cookers.

Question 18

A student wants to obtain a magnified image of an object AB as on a screen. Which one of the following arrangements shows the correct position of AB for him/her to be successful?

1.

2.

3.

4.

Answer

Reason — When the object is kept between F and 2F, enlarged, real and inverted image is obtained on the screen.

Question 19

The following diagram shows the use of an optical device to perform an experiment of light. As per the arrangement shown, the optical device is likely to be a;

1. Concave mirror
2. Concave lens
3. Convex mirror
4. Convex lens

Answer

Concave lens

Reason — As the rays are passing through the device so it should be a lens and as we can see that the rays are diverging, hence it is a concave lens.

Question 20

A ray of light starting from the air passes through medium A of refractive index 1.50, enters medium B of refractive index 1.33 and finally enters medium C of refractive index 2.42. If this ray emerges out in the air from C, then for which of the following pairs of media the bending of light is least?

1. air-A
2. A-B
3. B-C
4. C-air

Answer

A-B

Reason — The bending of light is least when the refractive index change is least. When light is travelling from medium A to medium B, the change in refractive index is from 1.50 to 1.33 which is the least in this case. Hence, the bending of light is also the least for A-B.

Question 21

Which of the following statements is not true for the scattering of light?

1. Colour of the scattered light depends on the size of particles of the atmosphere.
2. Red light is least scattered in the atmosphere.
3. Scattering of light takes place as various colours of white light travel with different speeds in air.
4. The fine particles in the atmospheric air scatter the blue light more strongly than red. So the scattered blue light enters our eyes.

Answer

Scattering of light takes place as various colours of white light travel with different speeds in air.

Reason — Various colours of white light travel with same speed in vacuum/air.

Question 22

For the diagram shown, according to the new cartesian sign convention the magnification of the image formed will have the following specifications :

1. Sign — Positive, Value — Less than 1
2. Sign — Positive, Value — More than 1
3. Sign — Negative, Value — Less than 1
4. Sign — Negative, Value — More than 1

Answer

Sign — Positive, Value — More than 1

Reason — When the object is kept between focus and the optical centre in a concave mirror, then the image formed is of larger size than object and the image is erect.

Question 23

A ray of light is incident as shown. If A, B and C are three different transparent media, then which among the following options is true for the given diagram?

1. ∠ 1 > ∠ 4
2. ∠ 1 < ∠ 2
3. ∠ 3 = ∠ 2
4. ∠ 3 > ∠ 4

Answer

∠ 3 = ∠ 2

Reason — As the two normals are parallel to each other, so ∠ 2 = ∠ 3 as they form a pair of alternate angles. Hence, ∠ 3 = ∠ 2 is true for the given diagram.

Question 24

In the diagram given below, X and Y are the end colours of the spectrum of white light. The colour of 'Y' represents the

1. Colour of the sky as seen from Earth during the day.
2. Colour of the sky as seen from the moon.
3. Colour used to paint the danger signals.
4. Colour of sun at the time of noon.

Answer

Colour used to paint the danger signals.

Reason — We can observe from the image that the Y colour has deviated the least. Hence, Y is red colour or the colour used to paint the danger signals.

Section B

Question 25

Which one of the following reactions is categorized as a thermal decomposition reaction?

1. 2H₂O (l) ⟶ 2H₂(g) + O₂ (g)
2. 2AgBr(s) ⟶ 2Ag(s) + Br₂(g)
3. 2AgCl(s) ⟶ 2Ag(s) + Cl₂(g)
4. CaCO₃(s) ⟶ CaO(s) + CO₂(g)

Answer

CaCO₃ (s) ⟶ CaO(s) + CO₂ (g)

Reason — The decomposition of CaCO₃ is carried out by heating hence the above reaction is a thermal decomposition reaction.

Question 26

Consider the pH value of the following acidic samples :

The decreasing order of their H⁺ ion concentration is

1. 3 > 4 > 1 > 2
2. 2 > 1 > 3 > 4
3. 2 > 1 > 4 > 3
4. 3 > 4 > 2 > 1

Answer

2 > 1 > 4 > 3

Reason — The number of H⁺ ion concentration determines the acidic strength of the sample. The pH and hydrogen ion concentration are inversely related i.e., as the value of pH increases, the H⁺ ion concentration decreases hence decreasing order of their H⁺ ion concentration is 2 > 1 > 4 > 3.

Question 27

Study the experimental set-up shown in given figure and choose the correct option from the following:

Answer

Reason — The reaction between potassium carbonate and HCl gas produces carbon dioxide gas.

K₂CO₃ + 2HCl (dil.) ⟶ 2KCl + H₂O + CO₂

Calcium hydroxide reacts with carbon dioxide gas and forms calcium carbonate, which turns the solution milky.

Ca(OH)₂ + CO₂ ⟶ CaCO₃ + H₂O

Question 28

Which one of the following structures correctly depicts the compound CaCl₂?

Answer

Reason — The valency of calcium is +2 and that of chlorine is -1. Two chlorine anions and one calcium cation form an ionic bond and the chemical formula of calcium chloride is CaCl₂.

Question 29

The pair(s) which will show displacement reaction is/are

(i) NaCl solution and copper metal

(ii) AgNO₃ solution and copper metal

(iii) Al₂(SO₄)₃ solution and magnesium metal

(iv) ZnSO₄ solution and iron metal

1. (ii) only
2. (ii) and (iii)
3. (iii) and (iv)
4. (i) and (ii)

Answer

(ii) and (iii)

Reason — AgNO₃ solution and copper metal will give displacement reaction where copper being more reactive than silver, displaces it from silver nitrate . Similarly, Al₂(SO₄)₃ solution and magnesium metal will give displacement reaction where magnesium being more reactive than aluminium, displaces it from aluminium sulphate.

Question 30

Which of the following salts do not have the water of crystallisation?

(i) Bleaching Powder

(ii) Plaster of Paris

(iii) Washing soda

(iv) Baking soda

1. (ii) and (iv)
2. (i) and (iii)
3. (ii) and (iii)
4. (i) and (iv)

Answer

(i) and (iv)

Reason — Bleaching Powder [CaOCl₂] and baking soda [NaHCO₃] do not have water of crystallization whereas plaster of Paris [CaSO₄.$\dfrac{1}{2}$ H₂O] and washing soda [Na₂CO₃.10H₂O] have.

Question 31

Assertion (A): Sodium hydrogen carbonate is used as an ingredient in antacids.

Reason (R): NaHCO₃ is a mild non-corrosive basic salt.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, and R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Reason — Sodium hydrogen carbonate [NaHCO₃] is used as an ingredient in antacids, as it is a mild non-corrosive basic salt and it neutralizes the excess acid produced in our stomach.

Question 32

Assertion (A): Burning of Natural gas is an endothermic process.

Reason (R): Methane gas combines with oxygen to produce carbon dioxide and water.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, and R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is false and R is true.

Reason — Burning of natural gas is an exothermic process and methane gas combines with oxygen to produce carbon dioxide and water.

CH₄ + 2O₂ ⟶ CO₂ + 2H₂O

Question 33

Assertion (A): Nitrogen is an essential element for plant growth and is taken up by plants in the form of inorganic nitrates or nitrites.

Reason (R): The soil is the nearest and richest source of raw materials like Nitrogen, Phosphorus and other minerals for the plants.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, and R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true, and R is not the correct explanation of A.

Reason — Nitrogen is changed into its nitrate or nitrite form by bacterial action.

Question 34

Assertion (A): Sun appears reddish at the time of Sunrise and Sunset.

Reason (R): Distance travelled by sunlight in the atmosphere is lesser during sunrise and sunset as compared to noon.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, and R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is true and R is false.

Reason — During the sunrise and sunset, the sun is near the horizon and most of the blue light and shorter wavelengths are scattered away by the particles. Therefore, the light that reaches our eyes is of longer wavelength. This gives rise to the reddish appearance of the sun.

During sunrise and sunset, sun is at a farther distance while at noon sun is directly overhead. Hence, distance travelled by sunlight in the atmosphere is more during sunrise and sunset as compared to noon.

Question 35

Assertion (A): Hydrochloric acid helps in the digestion of food in the stomach.

Reason (R): Hydrochloric acid creates an acidic medium to activate protein digesting enzymes.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, and R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true, and R is the correct explanation of A.

Reason — The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin by activating it.

Question 36

A student was asked to write a stepwise procedure to demonstrate that carbon dioxide is necessary for photosynthesis. He wrote the following steps. The wrongly worded step is:

1. Both potted plants are kept in dark rooms for at least three days.
2. Bottom of the bell jars is sealed to make them air tight.
3. Both potted plants are kept in sunlight after the starch test.
4. A leaf from both the plants is taken to test the presence of starch.

Answer

Both potted plants are kept in sunlight after the starch test.

Reason — Starch test is done after they have been kept in sunlight to know whether photosynthesis occurred or not.

Question 37

Respiratory structures of two different animals — a fish and a human being are as shown.

Observe (a) and (b) and select one characteristic that holds true for both of them.

1. Both are placed internally in the body of animal.
2. Both have thin and moist surface for gaseous exchange.
3. Both are poorly supplied with blood vessels to conserve energy.
4. In both the blood returns to the heart after being oxygenated.

Answer

Both have thin and moist surface for gaseous exchange.

Reason — Gills as well as alveoli have moist surface. Also, fishes have only two chambers to their hearts, and the blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body.

Question 38

Observe the diagram of an activity given below. What does it help to conclude, when the person exhales into the test-tube?

1. Percentage of carbon dioxide is more in inhaled air.
2. Fermentation occurs in the presence of oxygen.
3. Percentage of carbon dioxide is more in exhaled air.
4. Fermentation occurs in presence of carbon dioxide

Answer

Percentage of carbon dioxide is more in exhaled air.

Reason — Exhaling through the straw turns the lime water milky showing that percentage of carbon dioxide is more in exhaled air.

Question 39

If a lens can converge the sun rays at a point 20 cm away from its optical centre, the power of this lens is –

1. +2D
2. –2D
3. +5D
4. –5D

Answer

+5D

Reason — Given,

Convex lens as converging rays.

Focal length (f) = 20 cm

P = $\dfrac{100}{\text{f(cm)}}$

Substituting we get,

P = $\dfrac{100}{20}$ = +5D [positive sign as convex lens.]

Question 40

The radius of curvature of a converging mirror is 30 cm. At what distance from the mirror should an object be placed so as to obtain a virtual image?

1. Infinity
2. 30 cm
3. Between 15 cm and 30 cm
4. Between 0 cm and 15 cm

Answer

Between 0 cm and 15 cm

Reason — Given, concave mirror as it is a converging mirror.

R = 30 cm

We know, R = 2f

Substituting we get, 30 = 2 x f

f = $\dfrac{30}{2}$ = 15 cm

In a concave mirror, virtual image is obtained when the object is placed between focus and optical centre hence, object should be placed between 0 cm and 15 cm.

Question 41

The length of small intestine in a deer is more as compared to the length of small intestine of a tiger. The reason for this is :

1. Mode of intake of food
2. Type of food consumed
3. Presence or absence of villi in intestine
4. Presence or absence of digestive enzymes

Answer

Type of food consumed

Reason — The length of the small intestine differs in various animals depending on the food they eat. Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.

Question 42

Identify the two components of phloem tissue that help in transportation of food in plants.

1. Phloem parenchyma & sieve tubes
2. Sieve tubes & companion cells
3. Phloem parenchyma & companion cells
4. Phloem fibres and sieve tubes

Answer

Sieve tubes & companion cells

Reason— The translocation of food and other substances takes place in the sieve tubes with the help of adjacent companion cells both in upward and downward directions.

Question 43

A converging lens forms a three-times magnified image of an object, which can be taken on a screen. If the focal length of the lens is 30 cm, then the distance of the object from the lens is

1. –55 cm
2. –50 cm
3. –45 cm
4. –40 cm

Answer

–40 cm

Reason — Given, convex lens as converging lens

f = 30 cm

From formula,

m = $\dfrac{\text{v}}{\text{u}}$

-3 = $\dfrac{\text{v}}{\text{u}}$ [-ve sign as real and inverted image is formed.]

v = -3u

Using formula,

$\dfrac{1}{\text{f}}$ = $\dfrac{1}{\text{v}}$ - $\dfrac{1}{\text{u}}$

We get,

$\dfrac{1}{\text{30}}$ = $\dfrac{1}{\text{-3u}}$ - $\dfrac{1}{\text{u}}$

$\dfrac{1}{\text{30}}$ = $\dfrac{-1-3}{\text{3u}}$ = $\dfrac{-4}{\text{3u}}$

3u = -4 x 30

u = $\dfrac{-120}{3}$ = -40 cm

Hence, distance of the object from the lens = -40 cm.

Question 44

Which of the following statements is not true in reference to the diagram shown below?

1. Image formed is real.
2. Image formed is enlarged.
3. Image is formed at a distance equal to double the focal length.
4. Image formed is inverted.

Answer

Image formed is enlarged.

Reason — When object is placed at the centre of curvature (i.e. 2f), the image is formed at the same point and of same size as the object.

Question 45

In the diagram shown below n₁, n₂ and n₃ are refractive indices of the media 1, 2 and 3 respectively. Which one of the following is true in this case?

1. n₁ = n₂
2. n₁ > n₂
3. n₂ > n₃
4. n₃ > n₁

Answer

n₃ > n₁

Reason — According to the figure, the light ray bends towards the normal when it passes from medium 1 to medium 2 and then it bends further when it passes from medium 2 to 3. We know, ray of lights bends towards the normal when it passes from rarer to denser medium hence medium 3 is denser than medium 1 i.e., n₃ > n₁.

Question 46

The refractive index of medium A is 1.5 and that of medium B is 1.33. If the speed of light in the air is 3 × 10⁸ m/s, what is the speed of light in medium A and B respectively?

(a) 2 × 10⁸ m/s and 1.33 × 10⁸ m/s

(b) 1.33 × 10⁸ m/s and 2 × 10⁸ m/s

(c) 2.25 × 10⁸ m/s and 2 × 10⁸ m/s

(d) 2 × 10⁸ m/s and 2.25 × 10⁸ m/s

Answer

2 × 10⁸ m/s and 2.25 × 10⁸ m/s

Reason — We know,

refractive index of medium = $\dfrac{\text{speed of light in air}}{\text{speed of light in medium}}$

Substituting we get,

For medium A,

1.5 = $\dfrac{3 \times 10^8}{\text{speed of light in medium A}}$

speed of light in medium A = $\dfrac{3 \times 10^8}{1.5}$

Hence, speed of light in medium A = 2 × 10⁸ m/s

For medium B,

1.33 = $\dfrac{3 \times 10^8}{\text{speed of light in medium B}}$

speed of light in medium B = $\dfrac{3 \times 10^8}{1.33}$

Hence, speed of light in medium B =2.25 × 10⁸ m/s

Question 47

An object of height 4 cm is kept at a distance of 30 cm from the pole of a diverging mirror. If the focal length of the mirror is 10 cm, the height of the image formed is

1. +3.0 cm
2. +2.5 cm
3. +1.0 cm
4. +0.75 cm

Answer

+1.0 cm

Reason — Given, convex mirror as diverging mirror.

focal length (f) = 10 cm

u = -30 cm

h_o = 4 cm

v = ?

Using formula,

$\dfrac{1}{\text{f}}$ = $\dfrac{1}{\text{v}}$ + $\dfrac{1}{\text{u}}$

We get,

$\dfrac{1}{\text{10}}$ = $\dfrac{1}{\text{v}}$ - $\dfrac{1}{\text{30}}$

$\dfrac{1}{\text{v}}$ = $\dfrac{1}{\text{10}}$ + $\dfrac{1}{\text{30}}$

$\dfrac{1}{\text{v}}$ = $\dfrac{3+1}{\text{30}}$ = $\dfrac{4}{\text{30}}$

$\dfrac{1}{\text{v}}$ = $\dfrac{2}{\text{15}}$

v = $\dfrac{15}{\text{2}}$ = 7.5

m = - $\dfrac{\text{v}}{\text{u}}$ = $\dfrac{\text{h}_i}{\text{h}_o}$

Substituting we get,

-$\dfrac{7.5}{-30}$ = $\dfrac{\text{h}_i}{4}$

height of the image = $\dfrac{7.5 \times 4}{30}$ = +1 cm

Hence, height of the image = +1 cm

Question 48

50.0 mL of tap water was taken in a beaker. Hydrochloric acid was added drop by drop to water. The temperature and pH of the solution was noted. The following graph was obtained. Choose the correct statements related to this activity.

(i) The process of dissolving an acid in water is highly endothermic.

(ii) The pH of the solution increases rapidly on addition of acid.

(iii) The pH of the solution decreases rapidly on addition of acid.

(iv) The pH of tap water was around 7.0.

1. (i) and (ii)
2. (i) and (iii)
3. (iii) and (iv)
4. (ii) and (iv)

Answer

(iii) and (iv)

Reason — The pH of tap water was around 7.0 because tap water is a neutral solution. On addition of acid to water the heat energy is released hence the reaction is exothermic. The pH of the solution decreases rapidly from 3 to 1 with the addition of acid.

Section C

Case I

A student, took four metals P, Q, R and S and carried out different experiments to study the properties of metals. Some of the observations were :

• All metals could not be cut with a knife except metal R.
• Metal P combined with oxygen to form an oxide M₂O₃ which reacted with both acids and bases.
• Reaction with water.
  • P – Did not react either with cold or hot water but reacted with steam
  • Q – Reacted with hot water and the metal started floating
  • R – Reacted violently with cold water.
  • S – Did not react with water at all

Based on the above observations answer the following:

Question 49

Out of the given metals, the one which needs to be stored under Kerosene is

1. P
2. R
3. S
4. Q

Answer

R

Reason — R reacts vigorously and catches fire when kept in open, hence it needs to be stored in kerosene oil. Example : sodium and potassium

Question 50

Out of the given metals, the metal Q is

1. Iron
2. Zinc
3. Potassium
4. Magnesium

Answer

Magnesium

Reason — The metal Q is magnesium as it reacts with hot water only and starts floating due to the bubbles of hydrogen gas sticking to the surface.

Question 51

Metal which forms amphoteric oxides is

1. P
2. Q
3. R
4. S

Answer

P

Reason — The metal P combines with oxygen to form an amphoteric metal oxide M₂O₃ which reacted with both acids and bases.

Question 52

The increasing order of the reactivity of the four metals is;

1. P < Q < R < S
2. S < R < Q < P
3. S < P < Q < R
4. P < R < Q < S

Answer

S < P < Q < R

Reason — Based on the reactions of the above given metals with water, the increasing order of reactivity is S < P < Q < R .

Case II

The figure shown below represents a common type of dialysis called as Haemodialysis. It removes waste products from the blood such as excess salts, and urea which are insufficiently removed by the kidney in patients with kidney failure. During the procedure, the patient's blood is cleaned by filtration through a series of semi-permeable membrane before being returned to the blood of the patient. On the basis of this, answer the following questions:

Question 53

The haemodialyzer has semi-permeable lining of tubes which help to:

1. To maintain osmotic pressure of blood.
2. To filter nitrogenous wastes from the dialyzing solution.
3. In passing the waste products in the dialyzing solution.
4. To pump purified blood back into the body of the patient.

Answer

In passing the waste products in the dialyzing solution.

Reason — It allows the waste to pass from blood to dialyzing solution.

Question 54

Which one of the following is not a function of Artificial Kidney?

1. To remove nitrogenous wastes from the blood.
2. To remove excess fluids from the blood.
3. To reabsorb essential nutrient from the blood.
4. To filter and purify the blood.

Answer

To reabsorb essential nutrient from the blood.

Reason — Reabsorption of nutrient occurs only in kidney.

Question 55

The 'used dialysing' solution is rich in:

1. Urea and excess salts
2. Blood cells
3. Lymph
4. Proteins

Answer

Urea and excess salts

Reason — The Urea and excess salts move into the the dialyzing solution from the blood.

Question 56

Which part of the nephron in human kidney, serves the function of reabsorption of certain substances?

1. Glomerulus
2. Bowman's capsule
3. Tubules
4. Collecting duct

Answer

Tubules

Reason — Reabsorption occurs in Proximal convoluted tubule of nephron.

Case III

A compound microscope is an instrument that consists of two lenses L₁ and L₂. The lens L₁ called objective forms a real, inverted and magnified image of the given object. This serves as the object for the second lens L₂; the eyepiece. The eyepiece functions as a simple microscope or magnifier. It produces the final image, which is inverted with respect to the original object, enlarged and virtual.

Question 57

What types of lenses must be L₁ and L₂?

1. Both concave
2. Both convex
3. L₁ – concave and L₂– convex
4. L₁ – convex and L₂ – concave

Answer

Both convex

Reason — A compound microscope is made up of two convergent lens i.e., two convex lens.

Question 58

What is the value and sign of magnification (according to the new Cartesian sign convention) of the image formed by L₁?

1. Value = Less than 1 and Sign = Positive
2. Value = More than 1 and Sign = Positive
3. Value = Less than 1 and Sign = Negative
4. Value = More than 1 and Sign = Negative

Answer

Value = More than 1 and Sign = Negative

Reason — The image formed is magnified and inverted, hence the magnification is more than one and with negative sign.

Question 59

What is the value and sign of (according to the new Cartesian sign convention) magnification of the image formed by L₂?

1. Value = Less than 1 and Sign = Positive
2. Value = More than 1 and Sign = Positive
3. Value = Less than 1 and Sign = Negative
4. Value = More than 1 and Sign = Negative

Answer

Value = More than 1 and Sign = Negative

Reason — The image formed is magnified and inverted, hence the magnification is more than one and with negative sign.

Question 60

If the power of the eyepiece (L₂) is 5 diopters and it forms an image at a distance of 80 cm from its optical centre, at what distance should the object be?

1. 12 cm
2. 16 cm
3. 18 cm
4. 20 cm

Answer

16 cm

Reason — Given,

Power = +5D [convex lens has positive sign]

v = -80 cm.

u = ?

From formula,

P = $\dfrac{100}{\text{f(cm)}}$

Substituting we get,

5 = $\dfrac{100}{f}$

f = $\dfrac{100}{5}$ = 20 cm

Using formula,

$\dfrac{1}{\text{f}}$ = $\dfrac{1}{\text{v}}$ - $\dfrac{1}{\text{u}}$

We get,

$\dfrac{1}{\text{20}}$ = $\dfrac{1}{\text{-80}}$ - $\dfrac{1}{\text{u}}$

$\dfrac{1}{\text{u}}$ = -$\dfrac{1}{\text{80}}$ - $\dfrac{1}{\text{20}}$

$\dfrac{1}{\text{u}}$ = $\dfrac{-1-4}{\text{80}}$ = $\dfrac{-5}{\text{80}}$

$\dfrac{1}{\text{u}}$ = $-\dfrac{1}{\text{16}}$

u = -16

Hence, distance of the object from the lens = 16 cm.