Consider the following statements regarding nitrogen : I. Nitrogen contains a triple bond. II. Nitrogen is a triatomic gas. III. Forces acting between nitrogen molecules are weak van der Waals forces. Which of the statements given above are correct?
- A.I and II only
- B.II and III only
- C.I and III only
- D.I, II and III
Correct answer
Explanation
The correct answer is C, I and III only. A nitrogen molecule, N₂, is diatomic, not triatomic; its two atoms are joined by a triple bond, and the molecules attract each other only weakly.
Each nitrogen atom has five valence electrons and shares three with the other atom, forming N≡N. This triple bond is one of the strongest in chemistry (about 946 kJ/mol), which is why nitrogen gas is so unreactive and is used to fill food packets and tyres. Because N₂ is small and non-polar, only weak van der Waals (dispersion) forces act between its molecules, so it boils at a very low −196°C and is a gas at room temperature.
A is wrong because it includes statement II, which is false.
B is wrong because it includes statement II and leaves out statement I, which is true.
D is wrong because statement II is false: nitrogen gas has two atoms per molecule, while ozone (O₃) is an example of a triatomic gas.
Exam tip: N₂ – diatomic, N≡N triple bond, very inert, boils at −196°C.
Practice Questions
View allWhich 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:
- A.1, 3 and 4 only
- B.1, 3, 5 and 6 only
- C.2, 4, 5 and 6 only
- D.1, 2, 4, 5 and 6
Show answer
Alfalfa, chickpea and clover are legumes, and legumes fix nitrogen. Plants of the legume family (Fabaceae) carry root nodules that house Rhizobium bacteria.
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- A.Alpha and Beta radiations only
- B.Alpha and Gamma radiations only
- C.Beta and Gamma radiations only
- D.Alpha, Beta and Gamma radiations
Show answer
Neither beta nor gamma emission changes the total number of protons and neutrons in a nucleus, so the mass number stays the same.
Read the full explanation →Which one among the following statements about facilitated transport in plants is correct?
- A.All passive transports are types of facilitated transport.
- B.Facilitated transport is an example of active transport.
- C.Water moves across plasma membrane by active transport.
- D.Facilitated transport requires assistance of carrier proteins.
Show answer
In facilitated transport, molecules cross the membrane with the help of membrane proteins, while still moving down their concentration gradient.
Read the full explanation →Who among the following has coined the term 'Quark', the fundamental particles that make up protons and neutrons in an atomic nucleus ?
- A.Richard Feynman
- B.Murray Gell-Mann
- C.Albert Einstein
- D.Niels Bohr
Show answer
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.
Read the full explanation →The spindle fibre is attached to which of the following specific regions of the chromosomes?
- A.Kinetochore
- B.Chromonema
- C.Telomere
- D.Centriole
Show answer
Spindle fibres attach to the kinetochore, a disc-shaped protein structure on the centromere of each chromosome. During cell division the spindle, made of microtubules, pulls the copies of each chromosome apart.
Read the full explanation →