1. A transition element. - (b) Nickel

2. A transuranium element. - (d) Plutonium

3. Reduces Fe₂SO₃ at high temperatures in the thermit process. - (a) Aluminium

4. Present in the alloy bell metal. - (c) Tin

The electrical conductivity increases because sulfuric acid dissociates into ions (H⁺ and SO₄²⁻), which carry electric current, unlike pure water.

Or

The carriers of electricity during electrolysis are ions—cations (positive) and anions (negative).

During the electrolysis of an aqueous solution of CuSO₄ using copper electrodes, the Cu²⁺ (copper ions) migrate towards the cathode. At the cathode, these ions gain electrons and are deposited as copper metal.

When H_₂S gas is passed through an acidified aqueous solution of potassium dichromate, the solution changes from orange to green due to the reduction of dichromate ions (Cr₂O₇²⁻) to chromium ions (Cr³⁺).

The other substance used in the production of urea, besides ammonia, is carbon dioxide (CO₂).

One use of poly (vinyl chloride) (PVC) is in the production of pipes for plumbing and irrigation systems.

OR

An isomer of CH₃CH₂OH (ethanol) is dimethyl ether (CH₃OCH₃).

Here is its constitutional formula:

H₃C—O—CH₃.

This is an example of a functional group isomer, where ethanol is an alcohol and dimethyl ether is an ether.

Initial volume (V₁) = 52 m³

Initial Pressure (P₁) = 760 cm Hg

Final Pressure (P₂) = 104 cm Hg

Boyle's Law: P₁V₁ = P₂V₂

V₂ = 760 × 52 ÷ 104 = 380 m³

So, the volume of the gas at a pressure of 104 cm Hg, with temperature remaining constant, is 380 m³.

OR

Pressure (P) = 4 atm

Volume (V) = ?

Gas Constant (R) = 0.082 L atm mol^-1 K^-1

Temperature (T) = 300 K

No of mole (n) = 8/2 = 4 mol

We know, PV = nRT

or, V = nRT/P = 4 × 0.082 × 300 / 4 = 24.6 liters

So, the volume of 8 g of H₂ gas at the given conditions is 24.6 liters.

The refractive index of a medium (n) is inversely related to the velocity of light (v) in that medium. It is given by:

n = c/v

OR

Concave mirrors are used in the headlights of cars to produce a parallel beam of light covering a longer distance on the road.

Two advantages of using a CFL (Compact Fluorescent Lamp) over an incandescent lamp are:

1. Energy Efficiency: CFLs use less electricity.
2. Longer Lifespan: CFLs last much longer.