DCOA Mixed Practice Test #121

Question 1

Diazonium salts are formed from:‌​‍

Accepted Answer

Aromatic primary amines + HNO₂ (at 0-5°C) — Ar-NH₂ + HNO₂ + HCl → Ar-N₂⁺Cl⁻. Coupling with phenol/amines gives azo dyes.‌​‍

Answer

Aliphatic amines

Answer

Ketones

Answer

Only alcohols

Question 2

Power of a lens:

Accepted Answer

1/f (metres), in dioptre — P = 1/f. Positive for convex, negative for concave. 1 D = 1 m⁻¹.

Answer

f

Answer

f²

Answer

1/f²

Question 3

Efficiency of Carnot engine operating between T1 (hot) and T2 (cold) is:‌​‍

Accepted Answer

1 - T2/T1 — Maximum possible efficiency. Approaches 1 only if T2 → 0 K (unattainable).‌​‍

Answer

T2/T1

Answer

T1/T2

Answer

1 - T1/T2

Question 4

Chandrayaan-3 successfully landed on the Moon on:‌​‍

Accepted Answer

23 August 2023 — Chandrayaan-3's Vikram lander successfully soft-landed on the Moon's south pole on 23 August 2023, making India the 4th country to land on the Moon.‌​‍

Answer

23 July 2023

Answer

14 September 2023

Answer

23 October 2023

Question 5

Annelida (earthworm, leech) have:‌​‍

Accepted Answer

True coelom, metameric segmentation, closed circulation — Setae on body. ‌​‍Earthworm important for soil fertility. Hirudin from leeches — anticoagulant.

Answer

Open circulation

Answer

No coelom

Answer

Radial symmetry

Question 6

Newton's Third Law of Motion states that:‌​‍

Accepted Answer

For every action there is an equal and opposite reaction — Action-reaction pairs act on different bodies with equal magnitude, opposite direction.‌​‍

Answer

Force is always positive

Answer

Inertia is proportional to mass

Answer

Momentum is conserved

Question 7

India became the ____ country to soft-land on the Moon:‌​‍

Accepted Answer

4th — 4th country (after USA, Russia, China) with Chandrayaan-3 on 23 August 2023.‌​‍

Answer

2nd

Answer

3rd

Answer

5th

Question 8

Raja Rao is known for his novel:

Accepted Answer

Kanthapura — Raja Rao's 'Kanthapura' (1938) depicts the impact of Gandhi's movement on a South Indian village.

Answer

Untouchable

Answer

Train to Pakistan

Answer

The English Teacher

Question 9

An optic device that inverts image with known magnification, using two lenses, is:

Accepted Answer

Compound microscope — Compound microscope has objective + eyepiece for high magnification; inverted real image viewed via eyepiece.

Answer

Magnifying glass

Answer

Simple microscope

Answer

Periscope

Question 10

The element used as a moderator in nuclear reactors (heavy water) is:‌​‍

Accepted Answer

Deuterium (²H) — Heavy water D₂O uses deuterium; slows neutrons without absorbing them.‌​‍

Answer

Ordinary hydrogen

Answer

Helium

Answer

Tritium (³H)

DCOA Mixed Practice Test #121