Railway Science (Chemistry-Structure of Atom) (Part-II)

Total Questions: 50

11. Which of the following statements is/are true /false ? [RRB Group D 22/10/2018 (Afternoon)]

A. An ion is a charged particle and can be negatively or positively charged. A negatively charged ion is called an anion and a positively charged ion, a cation
B. An ion is a charged particle and can be negative or positively charged. A negatively charged ion is called a cation and a positively charged ion, an anion.

Correct Answer: (b) Only A is true
Solution:

An ion is an atom or molecule with a positive or negative charge. Cations are positively charged ions formed when metals lose electrons, while anions are negatively charged ions formed when nonmetals gain electrons.

12. How many atoms are there in one molecule of ammonium chloride ? [RRB Group D 22/10/2018 (Evening)]

Correct Answer: (d) 6
Solution:

Ammonium chloride (NH₄Cl) consists of one nitrogen atom (N), four hydrogen atoms (H), and one chlorine atom (Cl). Therefore, the total number of atoms in one molecule of ammonium chloride is: 1 nitrogen atom (N) + 4 hydrogen atoms (H) + 1 chlorine atom (Cl) = 6 atoms.

13. The maximum number of electrons that can be accommodated in the fourth energy level is: [RRB Group D 23/10/2018 (Afternoon)]

Correct Answer: (b) 32
Solution:

Each energy level in an atom can hold a specific number of electrons based on the formula 2n² , where n is the energy level number. For the fourth energy level (n = 4), the calculation is: 2 × (4)² = 2 × 16 = 32.

14. Which of the following compounds has the maximum number of atoms ? [RRB Group D 23/10/2018 (Evening)]

Correct Answer: (d) H₂SO₄
Solution:

Total number of atoms -  H₂SO₄ = 2(H), 4(O) = 2 + 1 + 4 = 7.
Ca(OH)₂ = 1 (Ca), 2(O), 2(H) = 1 + 2 + 2 = 5.
HNO₂ = 1(H), 1(N), 2(O) = 1 + 1 + 2 = 4.
CO₂ = 1(C), 2(O) = 1 + 2 = 3

15. What is the atomicity of phosphorus ? [RRB Group D 24/10/2018 (Morning)]

Correct Answer: (d) quaternary atom
Solution:

Atomicity - It is the total number of atoms present in a molecule of an element. Types - Monatomic: Composed of one atom e.g. He (Helium), Ne (Neon), Ar (Argon). Diatomic: Composed of two atoms e.g. H₂ (Hydrogen), N₂ (Nitrogen). Triatomic: Composed of three atoms e.g. O₃ (Ozone). Polyatomic: Composed of three or more atoms e.g. P₄ (Phosphorus), S₈ (Sulfur).

16. What is the atomicity of sulfur ? [RRB Group D 25/10/2018 (Afternoon)]

Correct Answer: (a) Polyatomic
Solution:

The element consists of three or more atoms. Examples: Phosphorus (P) as P₄ and sulfur (S) as S₈ . Triatomic – The element which consists of three atoms. Diatomic – The element which consists of two atoms. Monoatomic – when an element consists of a single atom.

17. The atomicity of sulfur is ______. [RRB Group D 26/10/2018 (Afternoon)]

Correct Answer: (c) polyatomic
Solution:

Clusters of atoms that act as an ion are called polyatomic ions. They carry a fixed charge on them. Atomicity of some elements - Non-Metal: Argon - Monotomic, Helium - Monoatomic, Oxygen - Diatomic, Hydrogen - Diatomic, Nitrogen - Diatomic, Chlorine - Diatomic, Phosphorus - Tetra-atomic.

18. Which of the following elements has the largest - size ions ? [RRB Group D 29/10/2018 (Morning)]

Correct Answer: (a) P
Solution:

(Phosphorus, group 15, Period 3, Atomic number (Z) = 15). From right to left in the periodic table the atomic radius increases, the effective nuclear charge also increases. As Ar is the 18 group element, Cl is the 17 group element, S is the 16 group element, and P is the 15 group element so P has the largest- size ions among these elements.

19. How many atoms are present in a molecule of Ca(OH)₂ ? [RRB Group D 31/10/2018 (Afternoon)]

Correct Answer: (b) 5
Solution:

A molecule of Ca(OH)₂ consists of one calcium atom, two oxygen atoms, and two hydrogen atoms, for a total of five atoms. Ca(OH)₂ is also known as calcium hydroxide, a compound used in various industrial and agricultural applications.

20. Which of the following is not true about atoms? [RRB Group D 12/11/2018 (Morning)]

Correct Answer: (a) Atoms of two elements are similar.
Solution:

Atoms of different elements have different numbers of protons in their nuclei, which determines their chemical properties.