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 is in packaging materials, such as aluminium foil.

Acidic foods should not be kept in an aluminium container because they can react with the metal, leading to the leaching of metal into the food, which alters the taste and poses health risks due to potential neurotoxicity from high aluminium intake.

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

Gases which obey the PV=RT (for 1 mole) equation at all temperature and pressure are called ideal gases.

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

⇒ \text{R}_\text{A}\over \text{R}_\text{B} = ({r_B})^2\over ({2r_B})^2

⇒ \text{R}_\text{A}\over \text{R}_\text{B} = ({r_B})^2\over 4({r_B})^2

⇒ \text{R}_\text{A}\over \text{R}_\text{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