Explanation

Raney nickel is prepared by treating a nickel-aluminum (Ni-Al) alloy with concentrated NaOH.

This process removes aluminum, leaving behind porous nickel, which acts as an excellent hydrogenation catalyst.

Explanation

Water (H₂O) is composed of 2 hydrogen atoms (1g each) and 1 oxygen atom (16g) → total molar mass = 18g.

Percentage of oxygen = (16/18) × 100 = 88.8% by mass.

Explanation

Choanocytes, also called collar cells, are flagellated cells found in parazoans (sponges).

They help in capturing food particles and aiding digestion by creating a water current.

Explanation

Laughing gas is the common name for nitrous oxide (N₂O), a colorless gas with a slightly sweet smell.

It acts as a mild anesthetic and analgesic.

It is often used in dentistry and surgery.

Explanation

A semiconductor has electrical properties between a conductor and an insulator.

It conducts electricity under certain conditions, making it essential in electronic devices.

Explanation

A liquid with very high vapour pressure boils at a lower temperature because it reaches atmospheric pressure more quickly.

Boiling occurs when vapour pressure equals external pressure — higher vapour pressure means this happens sooner.

Explanation

Atomicity refers to the number of atoms present in a single molecule of an element or compound.

For example, O₂ has an atomicity of 2, while P₄ has an atomicity of 4.

Explanation

Inflorescence refers to the arrangement or pattern of flowers on the floral axis or stem.

It can be simple or compound, with types like raceme, panicle, or capitulum.

Explanation

A mass attached to a spring oscillates back and forth around an equilibrium position, following Hooke's Law.

This periodic motion with a restoring force proportional to displacement defines simple harmonic motion (SHM).

Explanation

Rudolph Virchow proposed in 1855 that all new cells arise from pre-existing cells (“Omnis cellula e cellula”).

This idea supported the cell theory, challenging the earlier belief in spontaneous generation.