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Class 12 Chemistry  MCQ Questions of The p-Block Elements with Answers?

Answer 1

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1. Boron shows diagonal relation with

(a) Al
(b) C
(c) Si
(d) Sn

2. Element found from sea water is

(a) magnesium
(b) Sodium
(c) Iodine
(d) None of these

3. The shape of XeF₄ is

(a) tetrahedral
(b) square planar
(c) pyramidal
(d) linear

4. Which one of the following does not form hydrogen bonding?

(a) NH₃
(b) H₂O
(c) HCl
(d) HF

5. Modern periodic table is given by

(a) Debonair
(b) Mendeleef
(c) Mendel
(d) None of these

6. Which one of the following elements is found in free state in nature?

(a) Sodium
(b) Iron
(c) Zinc
(d) Gold

7. Which of the following is the strongest oxidising agent?

(a) F₂
(b) Cl₂
(c) l₂
(d) Br₂

8. Which of the following oxides is an hydride of nitrous acid?

(a) N₂O₃
(b) NO₂
(c) NO
(d) N₂O₄

9. Atomicity of phosphorus is

(a) 1
(b) 2
(c) 3
(d) 4

10. The structure of white phosphorus is

(a) square-planar
(b) pyramidal
(c) tetrahedral
(d) trigonal planar

11. PCl₃ on hydrolysis gives

(a) H₃PO₃
(b) HPO₃
(c) H₃PO₄
(d) POCl₃

12. Which of the following is a tetrabasic acid?

(a) Hypophosphorus acid
(b) Metaphosphoric acid
(c) Pyrophosphoric acid
(d) Orthophosphoric acid

13. The hybridisation of sulphur in sulphur hexafluoride is

(a) sp³d
(b) sp³d²
(c) sp³d³
(d) sp³

14. Sulphur molecule is

(a) diatomic
(b) triatomic
(c) tetratomic
(d) Octa-atomic

15. H₂S does not produce metallic sulphide with :

(a) CuCl₂
(b) COCl₂
(c) CdCl₂
(d) ZnCl₂

16. The mixture of concentrated HCl and HNO3 made in 3:1 ratio contains

(a) ClO₂
(b) NOCl
(c) NCl₃
(d) N₂O₄

17. The element which forms oxides in all oxidation states varying from +1 to +5 is

(a) N
(b) P
(c) As
(d) Sb

18. Collectively the elements of group 15 are called –

(a) pnicogens
(b) pnicopens
(c) nicopen
(d) None of these

19. Which one has the lowest boiling point?

(a) NH₃
(b) PH₃
(c) AsH₃
(d) SbH₃

20. The p-block element of group 15 that forms predominantly basic oxide is

(a) N
(b) P
(c) As
(d) Bi

21. Maximum covalency of nitrogen is ............................

(a) 3
(b) 5
(c) 4
(d) 6

22. The shape of ammonia molecule is

(a) tetrahedral
(b) pyramidal
(c) planar triangle
(d) octahedral

23. Which of the following can be used as an anaesthesia?

(a) N₂O
(b) NO
(c) NCl₃
(d) NO₂

24. Fluorine differs from rest of the halogens in some of its properties. This is due to

(a) its smaller size and high electronegativity
(b) lack of d-orbitals
(c) low bond dissociation energy
(d) All of the these

25. Helium is preferred to be used in balloons instead of hydrogen because it is

(a) incombustible
(b) lighter than hydrogen
(c) more abundant than hydrogen
(d) non polarizable

Answer 2

1. Answer : (c) Si

Explanation: Boron and silicon are diagonally related. Boron forms acidic oxide similar to silicon, unlike aluminum which forms amphoteric oxide.

2. Answer : (b) Sodium

Explanation: Sea water is salty because it contains sodium chloride in large amounts. Sodium chloride is also known as common salt. Therefore, both the elements sodium and chlorine are abundantly present in sea water.

3. Answer : (b) square planar

Explanation: According to the VSEPR theory, XeF₄ is sp³d² hybridized with 4 sigma bond pairs and 2 lone pairs on Xe. The lone pairs will occupy the perpendicular plane in an octahedral arrangement opposite (180°) from each other. Thus, XeF₄ is square-planar.

4. Answer : (c) HCl

Explanation: Hydrochloric acid (HCl) does not form hydrogen bonding. This is because in hydrogen bonding the bonding is formed between hydrogen and elements Nitrogen, Oxygen and Flourine. In Hydrochloric acid (HCl) there are no elements like Nitrogen, Oxygen and Flourine so it cannot form hydrogen bonding.

5. Answer : (b) Mendeleef

Explanation: In 1869, Russian chemist Dmitri Mendeleev created the framework that became the modern periodic table, leaving gaps for elements that were yet to be discovered. While arranging the elements according to their atomic weight, if he found that they did not fit into the group he would rearrange them.

6. Answer : (d) Gold

Explanation: Gold, silver, platinum, etc occur in free state. Since Gold, Platinum and Silver are the least reactive metals, hence they are found in free state in nature.

7. Answer : (a) F₂

Explanation: Fluorine is thought to be the most powerful elemental oxidizing agent.

8. Answer : (a) N₂O₃

Explanation: Two oxides of nitrogen are acid anhydrides; that is, they react with water to form nitrogen-containing oxyacids. Dinitrogen trioxide(N₂O₃) is the anhydride of nitrous acid, HNO₂, and dinitrogen pentoxide(N₂O₅) is the anhydride of nitric acid, HNO₃.

9. Answer : (d) 4

Explanation: Phosphorus exist as P₄ .So the atomicity is 4. Atomicity is the number of atoms of an element present in one molecule of that particular  element. The number of atoms present in a molecule of phosphorus are 4  atoms . So the atomicity of phosphorus is 4.

10. Answer : (c) tetrahedral

Explanation: White phosphorus exists as molecules made up of four atoms in a tetrahedral structure. The tetrahedral arrangement results in ring strain and instability. The molecule is described as consisting of six single P–P bonds. Two crystalline forms are known.

11. Answer : (a) H₃PO₃

Explanation: PCl₃ on hydrolysis gives fumes of phosphorous acid H₃PO₃ and HCl.

PCl₃ + 3H₂O → H₃PO₃ + 3HCl

12. Answer : (c) Pyrophosphoric acid

Explanation: Pyrophosphoric acid (H₄P₂O₇) contains four replaceable H-atoms. Hence, H₄P₂O₇ is a tetrabasic acid.

13. Answer : (b) sp³d²

Explanation: The sulfur atom in sulfur hexafluoride, SF₆, exhibits sp³d² hybridization. A molecule of sulfur hexafluoride has six bonding pairs of electrons connecting six fluorine atoms to a single sulfur atom.

14. Answer : (d) Octa-atomic

Explanation: Sulphur at room temperature, 'catenates' to form an octa-atomic molecule.More catenation means the formation of larger molecules which results in greater polarisability which in turn increases the probability of the formation of instantaneous dipoles.

15. Answer : (b) COCl₂

Explanation: H₂S does not produce metallic sulphide with COCl₂ (phosgene) because COCl₂ does not contain any metal ion.

16. Answer : (b) NOCl

Explanation: 3HCl + HNO₃ → NOCl + Cl₂ + H₂O

17. Answer : (a) N

Explanation: The element which forms oxides in all oxidation states +1 to +5 is. Nitrogen exhibits +1,+2,+3,+4, & +5 oxidation states when it reacts with oxygen.

18. Answer : (b) pnicopens

Explanation: Group 15 elements are also known as pnictogens because in Greek pigeon means to cholk or stifle. In the absence of the oxygen, molecular nitrogen has this property. That's why group 15 elements are known as either nitrogen family or pnictogens.

19. Answer : (b) PH₃

Explanation: Due to the absence of H-bonding, PH3 has the lowest b.p. The boiling point of the V group hydrides is : BiH₃ > SbH₃ > NH₃ > AsH₃ > PH₃

20. Answer : (d) Bi

Explanation: Bi forms basic oxides whereas N and P form acidic and As and Sb form amphoteric oxides.

21. Answer : (c) 4

Explanation: Nitrogen's maximum covalency is indeed 4. it does not break up its lone pair. Nitrogen's octet is complete as soon it bonds with three H atoms (aka forms ammonia). The fourth covalent bond is actually a coordinate covalent bond, formed when that nitrogen atom's lone pair gets donated to a proton.

22. Answer : (b) pyramidal

Explanation: The ammonia molecule has a trigonal pyramidal shape with the three hydrogen atoms and an unshared pair of electrons attached to the nitrogen atom.

23. Answer : (a) N₂O

Explanation: Nitrous oxide (N₂O) is a weak general anesthetic and is generally not used alone. It may be used in general anesthesia in a 70% concentration (in combination with 30% oxygen) or as a carrier gas with more potent general anesthetic agents.

24. Answer : (b) lack of d-orbitals

Explanation: Fluorine differs from rest of the elements of its family due to (i) its small size (ii) highest electronegativity, (iii) low bond dissociation energy and (iv) absence of d-orbitals in the valence shell.

25.  Answer : (a) incombustible

Explanation: Helium is used in balloons in place of hydrogen because it is incombustible. He do not catch fire like hydrogen. He is a inert element. 

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