Madhyamik Class 10 Physical Science Question Paper Solved 2018

c. CO₂

Explanation: Among the given greenhouse gases, CO₂ (carbon dioxide) has the maximum contribution to global warming.

(b)

Explanation: If you plot PV (product of pressure and volume) against P (pressure), the graph will be a horizontal straight line. This is because, according to Boyle’s Law, the product of pressure and volume remains constant for a given amount of gas at a constant temperature.

d. C₂H₂

Explanation: Molecular Mass = 2 × Vapour Density

= 2 × 13 = 26

• Molecular Mass of CO₂ = 44
• Molecular Mass of C₂H₄ = 28
• Molecular Mass of C₂H₆ = 30
• Molecular Mass of C₂H₂ = 26

c. °C^-1

d. Virtual and erect

Explanation: When an object is placed between the optical center and the focus of a convex lens, the rays diverge after refraction, making them appear to originate from a point on the same side as the object. This results in a virtual, erect, and magnified image.

a. 0°

Explanation: When a ray of light is incident perpendicularly (at 90° to the surface) on a transparent glass slab, it passes through the slab without bending. Since there is no change in direction, the angle of deviation is 0°.

d. ohm

Explanation: The SI unit of electrical resistance is the ohm (Ω). It is defined as the resistance between two points of a conductor when a constant potential difference of one volt, applied to these points, produces a current of one ampere.

b. live line

Explanation: In a domestic electric circuit, the fuse wire is connected to the live line. This is because the live wire carries the current.

a. a stream of electrons

Explanation: β-rays (beta rays) emitted from a radioactive element consist of a stream of electrons. These electrons are high-energy, high-speed particles that are emitted during beta decay.

d. 18

Explanation: The long form of the periodic table has 18 groups. These groups are columns in the table where elements share similar chemical properties.

b. LiH

Explanation: In LiH (lithium hydride), the octet rule is not obeyed because lithium requires only 2 electrons to achieve a stable configuration (duet rule), and hydrogen also needs just 2 electrons.

a. molten NaCl

Explanation: Molten NaCl can conduct electricity because, in its liquid form, sodium chloride dissociates into ions that are free to move.

c. Deep blue

Explanation: When excess aqueous ammonia is added to an aqueous solution of copper sulfate, a deep blue solution is formed.

b. Brass

Explanation: Brass is an alloy that contains zinc. It is primarily composed of copper and zinc. Bell metal, bronze, and duralumin do not contain zinc in their composition.

d. C₂H₆

Explanation: C₂H₆ (ethane) is a saturated hydrocarbon, meaning it contains only single bonds between carbon atoms. The other compounds, C₃H₆ (propene), C₂H₄ (ethylene), and C₂H₂ (ethyne), are unsaturated hydrocarbons with double or triple bonds.

Domestic cooking and lighting in villages.

OR

NO (nitric oxide) acts as a catalyst in breaking down ozone (O₃) into oxygen (O₂) in the ozone layer, thereby contributing to ozone depletion.

False

OR

Among iron, invar and copper invar has the least coefficient of linear expansion.

α <  β <  γ ray.

OR

Fusion reaction is the source of the sun’s energy.

Silver (Ag) is used as the cathode to electroplate silver over a copper spoon.

OR

Acetic acid (CH₃COOH).

One use of liquid ammonia is as a refrigerant in refrigeration systems.

OR

The formula of the precipitate formed when aqueous ammonia is added to an aqueous solution of aluminium chloride is Al(OH)₃ (aluminium hydroxide).

Propanal or Propan-1-al.

OR

The structural formula of the positional isomer of CH₃CH₂CH₂OH (1-propanol) is CH₃CH(OH)CH₃ (2-propanol).

Used as a coating in non-stick cookware due to its hydrophobic and high heat-resistant properties.

P₂ = 2P1, V₂ = V₁/2, T₁ = 273 K

From the combined gas equation : P_1V_1\over T_1=P_2V_2\over T_2

or, P_1V_1\over 273=2P_1V_1\over 2 × T_2

T₂ = 273 K

∴ Final temperature (T₂) = O ºC

OR

Initial Temperature (T₁) = 273 K,

Final Temperature (T₂) = 273 + 546 = 819 K

From Charle’s Law: V_1\over T_1=V_2\over T_2

⇒ V_1\over 273=V_2\over 819

⇒ V_2\over V_1=819\over 273

⇒ V₂ : V₁ = 3 : 1

If a ray of light passes through a Convex lens such that the direction of the emergent rays is parallel to the direction of the incident rays, then the path of the ray of light inside the lens intersects the principal axis at a particular point. This point is called the optical centre of the convex lens.

OR

The Earth’s sky appears blue during the daytime because blue light from the Sun is scattered more than other colours due to its shorter wavelength. This scattering causes the sky to look predominantly blue to our eyes.

According to Lewis’s concept, a covalent bond is formed when two atoms share a pair of electrons. For example, in a hydrogen molecule (H₂), each hydrogen atom shares its single electron with the other, forming a single covalent bond:

H⋅ + ⋅H → H − H

OR

The bond in sodium chloride (NaCl) cannot be expressed as Na-Cl because NaCl is an ionic compound, not a covalent one. Sodium (Na) donates an electron to chlorine (Cl), forming Na⁺ and Cl⁻ ions, which are held together by electrostatic forces rather than sharing electrons.

• Liquid covalent compound: Bromine (Br₂)
• Solid covalent compound: Diamond (a form of carbon)

When H₂S gas is passed through an aqueous copper sulfate (CuSO₄) solution, it reacts to form copper sulfide (CuS) and sulfuric acid (H₂SO₄). Balanced chemical equation:

CuSO₄​(aq) + H₂S(g) → CuS(s) + H₂SO₄ ​(aq)

When an aqueous solution of MSO₄ (where M is a metal) is electrolyzed, the cathode reaction is:

M²⁺(aq) + 2e⁻ → M (s)

Reason: This reaction is reduction because the metal cations (M²⁺) gain electrons (reduced) to form solid metal (M) at the cathode.

OR

Use of Copper:

• Electrical wiring – Copper is widely used for electrical wiring due to its excellent electrical conductivity.

Use of Aluminium:

• Aircraft construction – Aluminium is used in aircraft manufacturing because of its lightweight and high strength.

In the substitution reaction of methane with chlorine, the condition required is exposure to ultraviolet (UV) light or high temperatures. This initiates the reaction by generating chlorine radicals.

The balanced chemical equation for the first step (chlorination) is: CH₄ ​ + Cl₂ ​​ \overset \text{U V light} {\longrightarrow} CH₃Cl + HCl

OR

The balanced chemical equation for the reaction of ethanol with metallic sodium is:

2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂

In this reaction, ethanol (C₂H₅OH) reacts with sodium (Na) to form sodium ethoxide (C₂H₅ONa) and hydrogen gas (H₂).

The state of any gas can be completely be described by four variables such as pressure (P), Volume (V), Absolute temperature (T) and number of moles (n) of the gas.

According to Boyle’s law:

V ∝ 1/P (T and n are constant)

According to Charle’s law:

V ∝ T (P and n are constant)

According to Avogadro’s law:

V ∝ n (P and T are constant)

By method of compound variation: V ∝ nT/p,

When P, T and n of the gas vary

Therefore, V ∝ RnT/P (R = molar gas constant).

Or, PV = nRT. This equation is called the Ideal Gas Equation.

Balanced Chemical Eq

4FeS₂ + 11O₂ → 2Fe₂O₃ + 8SO₂

480 g                                    512 g

From the equation, it is evident that 480 g of FeS₂ is required to produce 512 g of SO₂

OR

According to the law of conservation of mass, the mass of the gaseous compound produced = 200 – 112 = 88 g

Molecular weight (M) = 2 × VD

= 2 × 22

= 44 g

Number of moles (n) = 88/44 = 2

The thermal conductivity of a material is the amount of heat which when passes normally in one second through the opposite faces of unit cube (i.e, 1 m cube), the difference in temperature between its 2 opposite faces is 1⁰C. The S.I. unit of thermal conductivity is J.m^-1.K^-1.s^-1.

OR

The coefficient of linear expansion of a substance is the change in length relative to its original length at 0ºC per unit of temperature.
The S.I. unit of the coefficient of linear expansion of a substance is K^-1.

When the object is placed between focus and the optical centre, an erect and magnified image be formed with the help of a convex lens.

Long Sightedness is rectified using a convex lens.

The R.I of a medium is given by,

μ  = Velocity of light in vacuum/Velocity of light in the medium

or, μ = 3 × 10^8\over 2 × 10^8

or, μ = 3\over2 = 1.5

OR

Refractive Index (μ) = sin\ i\over sin\ r

√2 = sin\ 45º\over sin\ r

sin r = sin\ 45º\over √2 

sin r = {1\over √2}\over √2

sin r = 1\over 2 = sin 30º

∠ r = 30º

Since refraction is taking place from rarer to denser medium,
angle of deviation,

δ = ∠ i – ∠ r  = 45⁰ – 30⁰ = 15⁰.

Joule’s law of heating :

If H amount of heat is produced in a conductor of resistance R, when a steady current I is passed through it for time t, then H is

1. directly proportional to the square of the current (H ∝ I²), when R and t are kept constant.
2. directly proportional to the resistance of the resistor (H ∝ R), when I and t are kept constant
3. directly proportional to the time for which the current flows through the resistor (H ∝ t), when I and R are kept constant.

Therefore, H = kI²Rt (k = Joule’s constant)

Resistance (r) of each part = 10\over2 = 5 Ω

Equivalent Resistance (R) = r × r\over r + r

= 5 × 5\over 5 + 5

= 2.5 Ω

OR

Energy consumed per day

By lamp = 2 × 60 × 5  = 600 Wh

By fan    = 2 × 80 × 5 = 800 Wh

Total energy consumed per day = 600 + 800 = 1400 Wh

Energy consumed in one month = 1400 × 30

= 42000 Wh

= 42 kWh or 42 BOT

Solution

Comparison of α and γ Rays:

1. Charge:

• α Rays: These are positively charged particles (helium nuclei) consisting of 2 protons and 2 neutrons.
• γ Rays: These are uncharged electromagnetic waves (gamma photons) and carry no electrical charge.

Ionizing Power:

• α Rays: Have high ionizing power. They ionize atoms more effectively because they are heavier and carry a charge. They can cause significant ionization in a small volume.
• γ Rays: Have low ionizing power. They penetrate materials more deeply but ionize fewer atoms along their path compared to α rays.

One use of radioactivity is in nuclear medicine for diagnostic imaging (e.g., PET scans) and treatment (e.g., radiotherapy for cancer).

Ionization energy is the amount of energy required to remove an electron from an atom or ion in its gaseous state to form a positively charged ion.

Increasing Order: Rb < K < Na < Li

OR

Similarity of Properties of Hydrogen:

With Group 1 Elements:

• Formation of Hydrides: Like alkali metals (Group 1), hydrogen forms hydrides (e.g., H₂O with oxygen, similar to how alkali metals form metal hydrides).

With Group 17 Elements:

• Formation of Acids: Hydrogen forms acids with halogens (Group 17 elements) such as HCl, HBr, and HI, similar to halogens forming hydrogen halides.
• Electron Configuration: Both hydrogen and halogens have a tendency to gain or share one electron to achieve a stable electronic configuration.

In the extraction of aluminium by electrolysis, cryolite (Na₃AlF₆) is added to the molten alumina (Al₂O₃). Cryolite lowers the melting point of the alumina and increases its conductivity, which makes the electrolytic process more efficient.

• Cathode: Carbon coating in the inner wall.
• Anode: Carbon rods.

Conditions for the Industrial Production of Ammonia by Haber’s Process:

1. Temperature: Typically around 450-500°C.
2. Pressure: Approximately 200-300 atmospheres.
3. Catalyst: Iron (Fe) with Molybdenum (Mo) as a promoter.
4. Reactants: Nitrogen (N₂) and hydrogen (H₂).

Balanced Chemical Equation:

N₂ (g) + 3H₂ (g) → 2NH₃ (g)

In this process, nitrogen and hydrogen gases react in the presence of an iron catalyst at high temperature and pressure to produce ammonia gas.

Identification of the Organic Compound: The compound with the molecular formula C₂H₄O₂ is acetic acid (CH₃COOH). It is soluble in water and reacts with sodium bicarbonate (NaHCO₃) to release carbon dioxide (CO₂), indicating it is a carboxylic acid.

Reaction with Ethanol:

Acetic acid reacts with ethanol in the presence of a catalyst (usually sulfuric acid) to form ethyl acetate through an esterification reaction.

Balanced Chemical Equation:

CH₃COOH + CH₃CH₂OH → CH₃​COOC_2​H₅​ + H₂​O

OR

Comparison of Properties of Organic and Inorganic Compounds:

Storms occur in the troposphere.

The alkaline earth metals are placed in Group 2 of the periodic table.

The two resistances must be connected in parallel.

The gas that smells like rotten eggs is hydrogen sulfide (H₂S).

The product of pressure and volume of 2 g of hydrogen at STP is 22.4 L·atm.

One common ore of copper is copper pyrites, also known as chalcopyrite.

• Name: Chalcopyrite
• Formula: CuFeS₂

A convex lens is called a convergent lens because it converges (brings together) parallel rays of light that pass through it.

When ethylene (C_₂H₄) reacts with bromine (Br₂), an addition reaction occurs. The double bond in ethylene breaks and bromine atoms add across the carbon atoms, forming 1,2-dibromoethane.

Balanced Chemical Equation:

C₂​H₄ ​+ Br₂​ → C_2​H_4​Br₂​

Resistance is derived from Ohm’s Law:

R = V/I

This means resistance (R) is the ratio of voltage (V) to current (I). It shows how much a material opposes the flow of electric current.