Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NDA 2025
Exam
NDA
Year
2025
Subject
General Ability
Chapter
General Science

NDA 2025 · General Ability · General Science

Which one of the following statements is NOT correct?

Which one of the following statements is NOT correct?

Options

  1. AWater of crystallization is the fixed number of water molecules present in one formula unit of a salt
  2. BThe molecular formula of Plaster of Paris is CaSO4⋅2H2OCaSO_4 \cdot 2H_2O
  3. CWashing soda is used for removing the permanent hardness of water
  4. DThe atmosphere of Venus is made up of thick white and yellow clouds of sulphuric acid

Correct answer

B. The molecular formula of Plaster of Paris is CaSO4⋅2H2OCaSO_4 \cdot 2H_2O

Step-by-step solution

Water of crystallization is the fixed number of water molecules present in one formula unit of a salt. This statement is correct.

The chemical formula of Plaster of Paris is CaSO4⋅12H2OCaSO_4 \cdot \dfrac{1}{2}H_2O (calcium sulphate hemihydrate). The formula CaSO4⋅2H2OCaSO_4 \cdot 2H_2O represents gypsum. Thus, this statement is incorrect.

Washing soda (Na_2CO_3 \cdot 10H_2O)isusedforremovingthepermanenthardnessofwaterbyprecipitatingcalciumandmagnesiumionsasinsolublecarbonates.Thisstatementiscorrect.<br><br>TheatmosphereofVenusismadeupofthickwhiteandyellowcloudsofsulphuricacid.Thisstatementiscorrect.<br><br>Answer:ThemolecularformulaofPlasterofParisis) is used for removing the permanent hardness of water by precipitating calcium and magnesium ions as insoluble carbonates. This statement is correct.<br><br>The atmosphere of Venus is made up of thick white and yellow clouds of sulphuric acid. This statement is correct.<br><br>Answer: The molecular formula of Plaster of Paris isCaSO_4 \cdot 2H_2O
Practice General Science on Quantrex Academy →

More from General Science

For an object in gravitational field, the gravitational potential is the same at two… NDA 2026A very large container consists of an ideal gas. The speed of sound in the gas is x .… NDA 2026A constant power machine pulls a block on a smooth horizontal surface. Which one of the… NDA 2026A ball is dropped from rest from height h above the ground in frame S (the Earth's… NDA 2026A pendulum of length L oscillates with an angular amplitude of θ = 60^ ^ ∘ and time… NDA 2026A solid of mass m has temperature-dependent specific heat as C(T) = C_0 + α T , where C_0… NDA 2026In a certain process, the relation between pressure (P) and volume (V) , for an ideal… NDA 2026An object is placed far beyond the centre of curvature of a concave mirror. The object… NDA 2026 Full General Science list All NDA PYQs