CBSE Class 12 Chemistry HOTs p Block Elements

Refer to CBSE Class 12 Chemistry HOTs p Block Elements. We have provided exhaustive High Order Thinking Skills (HOTS) questions and answers for Class 12 Chemistry Unit 7 The p-Block Elements. Designed for the 2025-26 exam session, these expert-curated analytical questions help students master important concepts and stay aligned with the latest CBSE, NCERT, and KVS curriculum.

Unit 7 The p-Block Elements Class 12 Chemistry HOTS with Solutions

Practicing Class 12 Chemistry HOTS Questions is important for scoring high in Chemistry. Use the detailed answers provided below to improve your problem-solving speed and Class 12 exam readiness.

HOTS Questions and Answers for Class 12 Chemistry Unit 7 The p-Block Elements

 

CHAPTER:7, p – BLOCK ELEMENTS

 

Case Based Questions :

 

Read the Passage given below and answer the following questions.
Ozone is an unstable, dark blue diamagnetic gas. It absorbs the UV radiations strongly, thus protecting the people on earth from the sun. The use of chlorofluorocarbons (CFC) in aerosol and refrigerator and their subsequent escape into the atmosphere, is blamed for making holes in the ozone layer over the Antartica..Ozone acts as a strong oxidising agent in acidic and alkaline medium. For this property, Ozone is used as a germicide and disinfectant for sterilizing water. It is also used in laboratory for the ozonolysis of organic compounds and in industry for the manufacture of potassium permanganate, artificial silk etc,
The following questions are multiple choice questions. Choose the most appropriate answer.

Question. Ozone acts as an oxidising agent due to
(a) Liberation of nascent oxygen
(b) Liberation of oxygen gas
(c) Both (a) and (b)
(d) None of these

Answer: A

Question. The colour of ozone molecule is
(a) White
(b) blue
(c) pale green
(d) Pale yellow

Answer: B

Question. Which of the following statement is not correct for ozone?
(a) It oxidises lead sulphide
(b) It oxidises KI
(c) It oxidises Mercury
(d) It cannot act as a bleaching agent in dry state.

Answer: D

Question. Ozone reacts with moist iodine gives
(a) HI
(b) HIO3
(c) I2O5
(d) I2O4

Answer: B

 

1 - MARK QUESTIONS

1. PCl3 fumes in moist air. Why? 1

2. Oxides of P, As, Sb exist as dimers (P4O6, P4O10, As4O6, and As4O10). Why? 1

3. P4O10 is used as dehydrating agent. Why? 1

4. Oxygen and sulphur exhibit –2 oxidation state where as others (Se, Te) exhibit +2 oxidation states. 1

5. Chemical methods are not practicable for the preparation of Fluorine. 1

6. Why H2SO4 is not used for the preparation of HBr from NaBr 1

7. Iodine forms I3 - ion but F2 does not form F3 - ion. Why? 1

8. NH3 has a higher proton affinity than PH3. Explain 1

9. Bleaching of flowers by chlorine is permanent while that by sulphur dioxide is temporary. Why? 1

10. Why does chlorine water loses its yellow colour on standing? 1

 

2 - MARKS QUESTIONS

11. Oxides of Nitrogen have open chain structure while those of phosphorous have closed chain or cage structure. Why is it so? Illustrate with one structural example for each type of oxide or the oxides of  phosphorous have cage structure but not open ones. 2

12. When a moist blue litmus paper is dipped in a solution of hypochlorous acid, it first turns red and then latter gets decolorized. Why? 2

13. Iodine is liberated when KI is added to a solution of Cu2+ ions but Cl2 is not liberated when KCl is added to a solution of Cu2+ ions. Why? Explain. 2

14. State the reasons

i. ClF3 exists but FCl3 does not

ii. BH4 - and NH4 + are isoloble 2

15. Why is it important to add KF in HF and exclude moisture during electrolysis of HF for the preparation of Fluorine ? 2

16. Why SO2 is a better reducing agent in alkaline medium as compared to that in acidic medium ? Explain.

 

3 - MARKS QUESTIONS
 
17. Account for the following:
 
(i) Chlorine water has both oxidizing and bleaching properties
 
(ii) H3PO2 and H3PO3 act as good reducing agents while H3PO4 does not.
 
(iii) On adding of ozone gas to KI solution, violet vapours are obtained 3
 
18. A translucent white waxy solid (A) on heating in an inert atmosphere is converted into its allotropic form (B). Allotrope (A) on reaction with very dilute aqueous KOH liberates a highly poisonous gas (C) having rotten fish smell. With
excess of chlorine (C) forms (D) which hydrolyses to compound (E). Identify A to E 3
 
19. An element ‘A’ exists as a yellow solid in standard state. It forms a volatile hydride ‘B’ which is a foul smelling gas and is extensively used in qualitative analysis of salts. When treated with oxygen, ‘B’ forms an oxide ‘C’ which is a
colourless, pungent smelling gas. This gas when passed through acidified KMnO4 solution, decolorizes it, ‘C’ gets oxidized to another oxide ‘D’ in the presence of a heterogeneous catalyst. Identify A, B, C, D and also give the chemical equation of reaction of “C’ with KMnO4 solution and for conversion of ‘C’ to ‘D’. 3
 
20. Element A burns in nitrogen to give an ionic compound B. The compound B reacts with water to give C and D. A solution of C becomes milky on bubbling carbondioxide. Identify A, B. C and D. And write the balanced equations. 3
 
 

1 Mark Questions

1. Which amongst the following is the strongest oxidizing agent?

ClO4 -, BrO4 -, IO4

2. A student wanted to draw his school building on a glass sheet, which acid he should use?

3. Nitrogen and P give negative ions, while As, Sb and Bi do not. Why?

4. Sea weeds are the sources of which halogen?

5. When NaBr is heated with conc H2SO4 ,Br2 is produced but when NaCl is heated with conc H2SO4, HCl is produced. Why?

6. Which oxo-acid of Phosphorus contains P-P linkage?

7. Out of HClO3 and HClO4, which has lower Pka value and why?

8. Name the acidic hydride of N2?

9. State the difference between the nature of Pi bonds in H3PO3 and HNO3 molecules?

10. Name the gas liberated when Ammonium Nitrate is strongly heated.

11. Give one disproportionation reaction of H3PO3.

 

2 Mark Questions
 
12. Oxides of Nitrogen have open chain structure, while those of Phosphorous have closed chain or cage structures. Why is it so?
 
13. Complete the following :
 
I. HNO3 + P4O10 →
II. IO3- + I- + H+  →
III. NH3 + NaOCl →
IV. SbCl3 + H2O →
 
14. Calculate the amount of 0.1 M NaOH solution required to neutralize the solution produced by dissolving 1.1 g of P4O6 in water.
 
15. Explain giving reason. Nitrogen exists as a diatomic molecule whereas Phosphorous exists as tetra atomic molecule.
 
16. Name the hydrogen halide which is liquid at room temperature and why?
 
17. Which oxide of sulphur is capable of acting as oxidizing as well as reducing agent? why?
 
18. (SiH3)3 N is a weaker base than (CH3)3 N. Give reason.
 
19. CN- ion is known but is CP- not known. Give reason.
 
20. Explain giving reason. NF3 is an exothermic compound but NCl3 is an endothermic compound.
 
21. Which halogen will produce O2 and O3 as passed through water?
 
22. Nitrogen forms a large no. of oxides than Phosphorous. Explain.
 
 
3 marks question
 
23. Account for the following
 
I. Chlorine water has both oxidizing and bleaching properties.
 
II. H3PO2 and H3PO3  act as good reducing agents while H3PO4  doesn’t.
 
24. An organic compound A gives a brick red flame on performing flame test. The compound gives the following tests also
I. It gives smell of chlorine when placed in moist air.
II. If KI and CH3COOH are added to the solution of the compound a violet colour is observed. 
Identify the compound and write the chemical reactions for the steps (I) and (II). III. The electron gain enthalpy value of F2 is less negative than chlorine.
 
25. Give reasons for each of the following observations
I. Only higher members of the group 18 of the periodic table are expected to form compounds.
II. NO2 readily forms a dimer whereas ClO2 doesn’t.
 
26. Give reasons for the following observations
I. SF6 is used as gaseous electrical insulators.
II. S exhibit greater tendency for catenation than selenion.
III. The electron gain enthalpy value of F2 is less negative than chlorine.
 
27. Bleaching of flowers by Cl2 is permanent, by SO2 it is temporary. Explain?
 
28. Hydrogen halides are covalent compounds but their aqueous solutions can conduct electric current. Explain.
 
29. Which of the halogens (except At)
I. Forms the weakest acid?
II. Has the largest atom?
III. Has the minimum ionization enthalpy?
IV. Has the maximum electron affinity?
 
30. Knowing the electron gain enthalpy values for O → O- and O → O2- as -141 KJ/mol and 702 Kj/mol respectively, how can you account for the formation of a large no. of oxides having O2- species and not O- (clue: Lattice Enthalpy).
 
31. What happens when SO2 is passed through an aq. Solution of Fe (III) salt. Give equation.
 
 
5 Marks Question
 
32. An element ‘A’ exists as a yellow solid in standard state. It forms a volatile hydride ‘B’which is a foul smelling gas and is extensively used in qualitative analysis of salts. When treated with oxygen, ‘B’ forms an oxide ‘C’ which is colourless, pungent
smelling gas. This gas when passed through acidified KMnO4 solution, decolourizes it. ‘C’ gets oxidized to another oxide ‘D’ in the presence of a Heterogeneous catalyst. Identify A, B, C, D and also give the chemical equation of reaction of ‘C’ with acidified KMnO4 solution and for conversion of ‘C’ to ‘D’.
 
33. Concentrated sulphuric acid is added followed by heating to each of the following test tubes labelled (i) to (v)
CBSE_Class_12_Chemistry_P_Block_1
(a) Formation of black substance
(b) Evolution of brown gas
(c) Evolution of colourless gas
(d) Formation of brown substance which on dilution becomes blue 
(e) Disappearance of yellow powder along with evolution of colourless gas.
 
34. When conc. sulphuric acid was added to an unknown salt present in a test tube, a brown gas (A) was evolved. This gas intensified when copper turnings were also added into this tube. On cooling, the gas ‘A’ changed into a colourless gas ‘B’.
(a) Identify the gases A and B.
(b) Write the equations for the reactions involved.
 
35. A translucent white waxy solid ‘A’ on heating in an inert atmosphere is converted in to its allotropic form (B). Allotrope ‘A’ on reaction with very dilute aqueous KOH librates a highly poisonous gas ‘C’ having rotten fish smell. With excess of chlorine ‘A’ forms ‘D’ which hydrolysis to compound ‘E’. Identify compounds ‘A’ to ‘E’ .
 
36. A colourless inorganic salt (A) decomposes completely at about 250 C to give only two products, (B) and (C), leaving no residue. The oxide (C) is a liquid at room temperature and neutral to moist litmus paper while the gas (B) is a neutral oxide. White phosphorus burns in excess of (B) to produce a strong white dehydrating agent. Write balanced equations for the reactions involved in the above process. Gradual addition of KI to Bi(NO3)3 solution initially produces a dark brown precipitate which dissolves in excess of KI to give a clear yellow solution. Write chemical equations for the a.
Unit 01 Solutions
CBSE Class 12 Chemistry HOTs Solutions
Unit 02 Electrochemistry
CBSE Class 12 Chemistry HOTs Electrochemistry
Unit 03 Chemical Kinetics
CBSE Class 12 Chemistry HOTs Chemical Kinetics
Unit 04 The d- and f-Block Elements
CBSE Class 12 Chemistry HOTs d and f block Elements
Unit 05 Coordination Compounds
CBSE Class 12 Chemistry HOTs Coordination Compounds
Unit 06 Haloalkanes and Haloarenes
CBSE Class 12 Chemistry HOTs Haloalkanes And Haloarenes
Unit 07 Alcohols, Phenols and Ethers
CBSE Class 12 Chemistry HOTs Alcohols Phenols And Ethers
Unit 08 Aldehydes, Ketones and Carboxylic Acids
CBSE Class 12 Chemistry HOTs Aldehyde Ketones And Carboxylic Acids
Unit 09 Amines
CBSE Class 12 Chemistry HOTs Animes
Unit 10 Biomolecules
CBSE Class 12 Chemistry HOTs Biomolecules
z More HOTs for Class 12 Chemistry
CBSE Class 12 Chemistry HOTs Answers to HOTs Question Database
~ Class 12 Chemistry (Old Chapters)
CBSE Class 12 Chemistry HOTs Chemistry in Everyday Life
CBSE Class 12 Chemistry HOTs General Principles And Processes Of Isolation Of Elements
CBSE Class 12 Chemistry HOTs Isolation of Elements
CBSE Class 12 Chemistry HOTs p Block Elements
CBSE Class 12 Chemistry HOTs Polymers
CBSE Class 12 Chemistry HOTs Surface Chemistry
CBSE Class 12 Chemistry HOTs The Solid State

Important Practice Resources for Class 12 Chemistry

HOTS for Unit 7 The p-Block Elements Chemistry Class 12

Students can now practice Higher Order Thinking Skills (HOTS) questions for Unit 7 The p-Block Elements to prepare for their upcoming school exams. This study material follows the latest syllabus for Class 12 Chemistry released by CBSE. These solved questions will help you to understand about each topic and also answer difficult questions in your Chemistry test.

NCERT Based Analytical Questions for Unit 7 The p-Block Elements

Our expert teachers have created these Chemistry HOTS by referring to the official NCERT book for Class 12. These solved exercises are great for students who want to become experts in all important topics of the chapter. After attempting these challenging questions should also check their work with our teacher prepared solutions. For a complete understanding, you can also refer to our NCERT solutions for Class 12 Chemistry available on our website.

Master Chemistry for Better Marks

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