Skip to content
GK24
Prime
General ScienceMediumAsked in: NDA · NDA-II 2018, GAT

Which one of the following is a tribasic acid?

  1. A.Hydrochloric acid
  2. B.Nitric acid
  3. C.Sulphuric acid
  4. D.Phosphoric acid

Correct answer

D. Phosphoric acid

Explanation

The correct answer is D, Phosphoric acid. Orthophosphoric acid, H3PO4, has three replaceable hydrogen ions, so it is tribasic.

The basicity of an acid is the number of hydrogen ions one molecule can give up in water. In H3PO4, all three hydrogens are attached to oxygen atoms and can ionise one after another, giving H2PO4−, HPO42− and PO43−. That is why it forms three series of salts, such as NaH2PO4, Na2HPO4 and Na3PO4. It is used in fertilisers, soft drinks and rust removers.

A is wrong because hydrochloric acid, HCl, gives one H+ and is monobasic.

B is wrong because nitric acid, HNO3, is also monobasic.

C is wrong because sulphuric acid, H2SO4, gives two H+ and is dibasic.

Exam tip: HCl and HNO3 monobasic, H2SO4 dibasic, H3PO4 tribasic.

Practice Questions

View all
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.