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General ScienceEasyAsked in: NDA · NDA-I 2025, GAT

Which one of the following is also known as Dry ice in its solid form?

  1. A.SiO₂
  2. B.CO₂
  3. C.CaO
  4. D.MgO

Correct answer

B. CO₂

Explanation

The correct answer is B, CO2. Solid carbon dioxide is called dry ice because it turns straight into gas without melting into a liquid, so it leaves nothing wet behind.

At normal atmospheric pressure carbon dioxide cannot exist as a liquid. Solid CO2 sublimes at about −78.5°C, which makes it a very cold and clean coolant. It is used to keep frozen food, ice cream and vaccines cold during transport, to make stage fog, and in laboratories as a cooling bath. Handling it with bare hands can cause frostbite, and in a closed room the released gas can push out oxygen.

A is wrong because SiO2 is silicon dioxide, the main compound in sand and quartz.

C is wrong because CaO is calcium oxide, known as quicklime.

D is wrong because MgO is magnesium oxide, a white powder used as an antacid and in heat-resistant bricks.

Exam tip: dry ice = solid CO2, sublimes at −78.5°C; quicklime = CaO, slaked lime = Ca(OH)2.

Practice Questions

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Q1.General ScienceAsked in: UPSC Civil Services · CSE Prelims 2022, GS Paper IMedium

Which of the following are nitrogen-fixing plants?

1. Alfalfa

2. Amaranth

3. Chickpea

4. Clover

5. Purslane (Kulfa)

6. Spinach

Select the correct answer using the code given below:

  1. A.1, 3 and 4 only
  2. B.1, 3, 5 and 6 only
  3. C.2, 4, 5 and 6 only
  4. D.1, 2, 4, 5 and 6
Show answer
Correct answer: A. 1, 3 and 4 only

Alfalfa, chickpea and clover are legumes, and legumes fix nitrogen. Plants of the legume family (Fabaceae) carry root nodules that house Rhizobium bacteria.

Q2.General ScienceAsked in: UPSC CAPF · CAPF 2017, Paper IMedium

The mass number of an element is NOT changed when it emits

  1. A.Alpha and Beta radiations only
  2. B.Alpha and Gamma radiations only
  3. C.Beta and Gamma radiations only
  4. D.Alpha, Beta and Gamma radiations
Show answer
Correct answer: C. Beta and Gamma radiations only

Neither beta nor gamma emission changes the total number of protons and neutrons in a nucleus, so the mass number stays the same.

Q3.General ScienceAsked in: UPSC CAPF · CAPF 2025, Paper IMedium

Which one among the following statements about facilitated transport in plants is correct?

  1. A.All passive transports are types of facilitated transport.
  2. B.Facilitated transport is an example of active transport.
  3. C.Water moves across plasma membrane by active transport.
  4. D.Facilitated transport requires assistance of carrier proteins.
Show answer
Correct answer: D. Facilitated transport requires assistance of carrier proteins.

In facilitated transport, molecules cross the membrane with the help of membrane proteins, while still moving down their concentration gradient.

Q4.General ScienceAsked in: UPSC CAPF · CAPF 2017, Paper IMedium

Who among the following has coined the term 'Quark', the fundamental particles that make up protons and neutrons in an atomic nucleus ?

  1. A.Richard Feynman
  2. B.Murray Gell-Mann
  3. C.Albert Einstein
  4. D.Niels Bohr
Show answer
Correct answer: B. Murray Gell-Mann

The American physicist Murray Gell-Mann proposed quarks in 1964 and gave them their name. Gell-Mann, and independently George Zweig, suggested that protons, neutrons and other such particles are built from smaller units.