Madhyamik Class 10 Physical Science Solved Paper 2023

c. CFCs

Explanation:

CFCs (chlorofluorocarbons) are the gases responsible for the depletion of the ozone layer. When released into the atmosphere, CFCs eventually reach the stratosphere, where they are broken down by ultraviolet (UV) light, releasing chlorine atoms. These chlorine atoms then react with ozone (O₃) molecules, leading to the depletion of the ozone layer.  

b. 2 RT

Explanation:

Number of mole (n) = 4/2 = 2

PV = nRT = 2RT

a. 32 g

Explanation:

C   +  O₂   ​→  CO_2​

12 g   32 g      44 g

From the balanced equation, 12 g of carbon requires 32 g of O₂

(c) 2

Explanation:

For liquids, two types of thermal expansion coefficients are defined:

1. Real (True) Expansion Coefficient – Refers to the actual expansion of the liquid itself.
2. Apparent Expansion Coefficient – Refers to the observed expansion when the liquid is in a container, since the container also expands.

c. red

Explanation:

Deviation depends on the refractive index of the medium for different wavelengths.

• Violet light has the shortest wavelength, hence it bends the most (maximum deviation).
• Red light has the longest wavelength, hence it bends the least (minimum deviation).

d. 45°

Explanation:

According to the law of reflection, the angle of incidence = angle of reflection (measured from the normal). Since the reflected ray makes an angle of 45° with the normal, the angle of incidence will also be 45°.

a. mho·meter⁻¹

d. 8 volts

Explanation:

Current (I) = 0.2 A

Resistence (R) = 4 ohm

Ohm’s law: V = I × R

V = 0.2 × 40 = 8 volt

a. α < β < γ

Explanation:

• α-rays have the least penetrating power because they are heavy and carry +2 charge.
• β-rays are lighter (electrons/positrons) and can penetrate more than α.
• γ-rays are electromagnetic waves with no mass/charge, so they penetrate the most.

b. 18

Explanation:

The 4th period starts with Potassium (K, Z=19) and ends with Krypton (Kr, Z=36).

Thus, it contains 18 elements in total.

c. 2

Explanation:

• Calcium (Z = 20) has electronic configuration: 2, 8, 8, 2 → it loses 2 electrons to become Ca²⁺.
• Oxygen (Z = 8) has electronic configuration: 2, 6 → it needs 2 electrons to complete its octet and become O²⁻.

Hence, in CaO formation, 2 electrons are transferred from Ca to O.

d. pure alumina.

Explanation:

a. NaNO₂ and NH₄Cl

Explanation:

In the laboratory, nitrogen gas is prepared by reacting sodium nitrite (NaNO₂) with ammonium chloride (NH₄Cl) in aqueous solution:

NaNO₂ + NH₄Cl → N₂ ↑ + 2H₂O + NaCl

b. ZnS

Explanation:

• Zinc blende is the chief ore of zinc, and its chemical formula is ZnS.
• Other important ores are ZnCO₃ (Calamine) and ZnO (Zincite), but ZnS = Zinc blende.

d. CH₃CH₂OH

Explanation:

• CH₃CH₂OH (Ethanol) contains the –OH functional group, so it is an alcohol.
• CH₃OCH₃ is an ether.
• CH₃CHO is an aldehyde.
• CH₃COOH is a carboxylic acid.

Nitrogen (N₂).

The calorific value of a sample of coal being 30,000 kJ/kg means that when one kilogram of this coal is completely burned, it releases 30,000 kilojoules of energy in the form of heat.

Wind energy can be used for sustainable growth development because it is a renewable resource.

The increase in volume is Y_o/273.

d. 1 : 4

Explanation:

At STP, equal volumes of gases contain equal numbers of molecules (Avogadro’s law).

So, molecules ∝ volume ⇒ (1 L H₂) : (4 L CO₂) = 1 : 4.

True.

OR

Diamond > Silver > Iron.

A convex mirror is commonly used as a rearview mirror in vehicles.

A ray that is parallel to the principal axis of a concave mirror, after reflection, will pass through the focal point (F) of the mirror.

No. For the same potential difference (V), length (L), and cross-section (A), the current depends on resistivity (ρ)

I-V graph

One peaceful use of atomic energy is nuclear power generation.

OR

Electromagnetic wave.

2.11.1 → (c) Ca

2.11.2 → (a) Fe

2.11.3 → (d) K

2.11.4 → (b) Zn

True.

The formation of an ionic compound is made possible largely by the formation of a stable ionic network (crystal lattice), which releases a large amount of lattice energy and stabilizes the compound.

In the refining of impure copper metal by the process of electrolysis, the mass of the cathode increases.

OR

In the electroplating of gold over silver, potassium gold cyanide (KAu(CN)₂) is commonly used as the electrolyte.

During electrolysis, electricity is carried through the electrolyte by ions.

One reason for the relative chemical inertness of N₂ (nitrogen gas) is its triple bond.

OR

Ammonia (NH₃)

The compound formed by the reaction of atmospheric nitrogen and oxygen as a result of lightning is nitrogen monoxide (NO).

The IUPAC name for CH₃CH=CH₂ is prop-1-ene.

OR

In methane (CH₄), the four valencies of carbon are disposed in a tetrahedral geometry.

Denatured spirit is used as a solvent and fuel in various industries.

Two possible future effects of global warming on the environment are:

• Increased Sea Level Rise: Melting ice caps will lead to coastal flooding and erosion.
• Extreme Weather Events: Global warming will cause more frequent and intense hurricanes, droughts, and heatwaves.

V₁ ​ = 580 cm³ (initial volume)

T₁ ​ = 17°C = 17 + 273.15 = 290.15 K

T₂ ​ = 47°C = 47+273.15 = 320.15K

V₂ ​ = ? (final volume)

Charles’s Law: V_1\over T_1 = V_2\over T_2

⇒ V₂ = V_1\over T_1 × T₂

⇒ V₂ = 580\over 290.15 × 320.15 = 638.16cm³

OR

Volume of Gas 1 (V₁) = 4480 mL

Volume of Gas 2 (V₂) = 5600 mL

For Gas 1: n₁ = 4480/22400 = 0.2 moles

For Gas 2: n₂ = 5600/22400 = 0.25 moles

From relation: M_1\over M_2 = n_2\over n_1

⇒ M_1\over M_2 = 0.25\over 0.2  = 5\over 4

The ratio of the molar masses of the two gases is 5:4.

Snell’s law : The ratio of the sine of the angle of incidence (i) to the sine of the angle of refraction (r) is a constant, for the light of a given colour and for the given pair of media.

Mathematical form: μ = sin i / sin r

OR

Characteristics of the Image 

• Upright (erect) and Virtual
• Enlarged

Electrical Heater Wire: Has a high resistance and High Melting Point.

Fuse Wire: Has a low melting point and low resistance.

Lewis dot diagram of CH₄

• Carbon shares one of its four valence electrons with each of the four hydrogen atoms.
• Each hydrogen atom shares its single electron with carbon.
• This sharing results in four covalent bonds.

Sodium chloride (NaCl) conducts electricity when dissolved in water, indicating it is composed of ions. Upon dissolution, NaCl dissociates into sodium ions (Na⁺) and chloride ions (Cl⁻), which are free to move in the solution, allowing it to conduct electric current. This behaviour confirms its ionic nature.

OR

Sodium chloride (NaCl) is formed through the transfer of an electron from sodium to chlorine, resulting in the formation of Na⁺ and Cl⁻ ions, which are held together by ionic bonds.

When hydrogen sulfide (H₂S) gas is passed through an aqueous solution of lead(II) nitrate (Pb(NO₃)₂), a chemical reaction occurs that results in the formation of lead(II) sulfide (PbS) as a precipitate and nitric acid (HNO₃) as a byproduct.

Balanced Chemical Equation:

H₂S(g) + Pb(NO₃)₂ ​ (aq) → PbS(s) ↓ + 2HNO₃ ​ (aq)

The reaction occurs at the cathode during the process of electrolysis.

This is a reduction reaction because it involves the gain of electrons.

OR

One use of aluminium: It is used in making utensils, foils, and lightweight vehicle parts.

Aluminium reacts with acids present in food (like citric acid, acetic acid, etc.), forming aluminium salts, some of which are toxic and can contaminate the food.

Polymerisation of ethylene: Ethylene is liquified at high pressure (1500-2000 atm). In the presence of catalysts such as peroxide, oxygen or chromium oxide and at temperatures 150℃-200℃, a large number of ethylene molecules join to form a white solid called polyethylene or polythene.

nC₂​H₄​→(C₂​H₄​​)_n

OR

The conversion of ethyne (HC≡CH) to ethane (CH₃CH₃) can be carried out through hydrogenation using platinum (Pt) as a catalyst.

HC = CH + H_2 ​ {\overset{Pt}{\longrightarrow}} CH₃​CH₃

A gas which obeys Boyle’s law, Charles’ law and Avogadro’s law for all values of temperature and pressures and which obeys the equation of state PV = nRT under all conditions of temperature and pressure is called an ideal gas.

The pressure of a gas in a closed container increases with an increase in temperature due to the kinetic theory of gases. As temperature rises, gas molecules move faster, leading to more frequent and forceful collisions with the container walls, which raises the pressure.

Balanced Chemical Equation:

S        +      O₂ →     SO₂

32 g         1 mol       22.4 L

(i) Amount of S required to produce 22.4 L of SO₂ = 32 g

⇒ Amount of S required to produce 2240 L of SO₂ = 32\over 22.4 × 2240 = 3200 g

(ii) The number of moles of oxygen required to produce 22.4 L of SO₂ = 1

⇒ The number of moles of oxygen required to produce 2240 L of SO₂ = 1\over 22.4 × 2240 = 100 mol

OR

Given Data

• Mass of solid compound burned = 480 g
• Mass of oxygen used = 352 g
• Mass of solid compound produced = 320 g
• Vapor density of gaseous compound = 32

Molar Mass = 2 × Vapor Density

= 2 × 32

= 64

Mass of gaseous compound=480 g + 352 g − 320 g

= 512 g

∴ Moles of gaseous compound = 512/64 = 8 mol

Definition: The coefficient of volume expansion of a solid is defined as the fractional increase in its volume per degree rise in temperature.

Coefficient of volume expansion (γ) = V_2 – V_1\over V_1(θ_2-θ_1)

OR

Examples of Thermal Expansion

• Solid: Railway Tracks – Railway tracks expand during hot weather, which can cause them to bend or warp if not properly spaced.
• Liquid: Thermometer – The mercury in a thermometer expands and rises when heated, allowing it to indicate temperature changes.
• Gas: Inflated Balloon – A balloon filled with air expands and may burst when heated, as the air inside takes up more space due to thermal expansion.

Angle of incidence (i) = 45º

Angle of refraction (r) = 60º

Angle of deviation (δ) = i − r

= 45º – 60º = −15º

The negative sign indicates that the deviation is towards the normal.

Given:

Object length (h) = 6 cm

Object distance (u) = – 2.4 cm

Image distance (v) = 4.8 cm

(i) Linear Magnification (m) = 4.8\over -2.4 = -2

(ii) Length of the Image = m × h = – 2 × 6 cm = -12 cm

The negative sign indicates that the image is inverted.

OR

Speed of light in vacuum = 3 × 10⁵ km/s

Speed of light in glass = 2 × 10⁵ Km/s

Speed of light in water = 2.25 × 10⁵ Km/s

μ_glass = 3 × 10^5\over 2 × 10^5 = 1.5

μ_water = 3 × 10^5\over 2.25 × 10^5 = 4/3

Ratio = μ_glass : μ_water = 1.5 : 4/3 = 9:8

Uses

1. X-ray: X-rays are commonly used in medical imaging to visualize the internal structures of the body, such as bones and teeth, helping in the diagnosis of fractures and other conditions.
2. γ-ray (Gamma-ray): Gamma rays are used in cancer treatment (radiotherapy) to target and destroy cancer cells.

Harmful Effect of γ-ray

One harmful effect of gamma rays is that they can cause DNA damage in living cells, potentially leading to mutations, cancer, or radiation sickness.

R = ρ {l}\over {a}

or,R = ρ {l}\over πr^2

⇒ R ∝  1\over r^2

⇒ {R_A} \over {R_B} = {{r_B}^2\over {r_A}^2

Given: r_A = 2r_B

⇒ R_A\over R_B = {{r_B}^2\over {2r_B}^2

⇒ R_A\over R_B = {{r_B}^2\over 4{r_B}^2

⇒ R_A\over R_B = 1\over 4

∴ The ratio of resistances of the two wires 1 : 4.

OR

Energy Consumption of the Lamps

• Power of each lamp = 60 W
• Total power for 3 lamps = 3 × 60 W = 180 W
• Daily energy consumption = 180 × 5 hours = 900Wh

Energy Consumption of the Fans

• Power of each fan = 100 W
• Total power for 2 fans = 2 × 100 W = 200 W
• Daily energy consumption = 200 W × 10 hours = 2000 Wh

Total Energy Consumption per Day

= 900Wh + 2000 Wh

= 2900 Wh

= 2.9 kWh

Total Energy Consumption (30 Day) = 2.9 kWh × 30

= 87 kWh

Total cost = ₹ 5 × 87 = ₹ 435

Faraday’s law of electromagnetic induction:

1. Whenever there is a change in magnetic flux linked with a coil, an emf is induced, which lasts as long as the change inmagnetic flux is linked with the coil changes.
2. The magnitude of the induced emf is directly proportional to the rate of change magnitude flux linked with the coil.

LED lamps are more energy-efficient as they consume significantly less power and last longer compared to incandescent lamps.

After the emission of an α-particle:

• Protons: 92 – 2 = 90
• Neutrons: 143 – 2 = 141

The new atom will have 90 protons and 141 neutrons.

The energy of stars is primarily produced by nuclear fusion reactions.

Mendeleev’s contributions to the creation of the periodic table include:

1. Periodic Law: He arranged elements in order of increasing atomic mass and discovered that elements with similar properties appeared at regular intervals (periodicity).
2. Predictions: Mendeleev left gaps in the table for undiscovered elements and accurately predicted their properties, such as gallium and germanium.
3. Grouping of Elements: He successfully grouped elements with similar chemical properties into columns, establishing the foundation for the modern periodic table.

OR

The atomic radius of an atom is the distance from the center of the nucleus to the outermost shell of electrons. It represents the size of the atom.

For group 14 elements (C, Si, Ge):

C < Si < Ge

Two Classes of Electrolytes:

1. Strong Electrolytes: Completely dissociate into ions in solution (e.g., sodium chloride, hydrochloric acid).
2. Weak Electrolytes: Partially dissociate into ions in solution (e.g., acetic acid, ammonium hydroxide).

Differentiation:

• Strong Electrolytes conduct electricity well due to full ionization.
• Weak Electrolytes conduct electricity poorly because they only partially ionize

Balanced Chemical Equation for the Haber Process: 

N₂ (g) + 3H₂ ​ (g) ⇌ 2NH₃ ​ (g)

Conditions of the Process:

1. Temperature: Approximately 450°C.
2. Pressure: Around 200 atmospheres.
3. Catalyst: Finely divided iron with promoters like potassium and aluminium oxides or molybdenum.

The hydrocarbon is methane (CH₄).

Balanced Chemical Equation for the First Step:

CH₄+ Cl₂ {\overset{\text{diffused sunlight}}{\longrightarrow}}  CH₃ + HCl

In this reaction, methane reacts with chlorine to form methyl chloride (CH₃Cl) and hydrogen chloride (HCl).

Use of Methane:

Methane is widely used as a fuel in domestic and industrial applications due to its high energy content.

OR

The primary industrial sources of LPG (Liquefied Petroleum Gas) are natural gas processing and crude oil refining.

Uses:

1. Acetic Acid: Used as a preservative and flavouring agent in food (e.g., vinegar).
2. Poly (tetrafluoroethylene): Commonly known as Teflon, it is used as a non-stick coating for cookware.

Carbon dioxide.

PV = nRT

= 1 × 0.082 × 273

= 22.4 atm L.

DC (Direct Current) is a type of electric current that flows in a single, constant direction. In a DC circuit, the electric charge (current) does not change direction.

γ-rays.

The structural formula of ethane:

Importance of Insulators in Household Wiring:

1. Safety: Prevents electric shock.
2. Prevents Short Circuits: Avoids electrical fires.
3. Efficiency: Reduces energy loss.
4. Durability: Protects against moisture and corrosion.

A concave lens is called a diverging lens.

Reason:

When parallel rays of light pass through a concave lens, they diverge or spread out after refraction.

When dilute sulfuric acid (H₂SO₄) is added to ferrous sulfide (FeS), a chemical reaction occurs, producing hydrogen sulfide gas (H₂S) which has a characteristic rotten egg smell and ferrous sulfate (FeSO₄).

Balanced Chemical Equation:

FeS + H₂SO₄ ​ →FeSO₄ ​ + H₂S

Reasons for Using Paper for Packaging:

1. Biodegradable: Paper is biodegradable and breaks down naturally, reducing environmental impact compared to plastic packaging.
2. Recyclable: Paper can be easily recycled, promoting sustainability and reducing the need for new raw materials.