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NCERT Solutions for Class 12 Chemistry Chapter 7 – The p-Block Elements

NCERT Solutions for Class 12 Chemistry Chapter 7 – The p-Block Elements is framed by a team of highly experienced chemistry teachers. This chapter is about the general trends in chemistry of groups 15, 16, 17 and 18. In this chapter, you will learn preparation, properties and uses of several compounds utilising these elements. The allotropic forms of some elements, the chemistry of interhalogen compounds, uses of noble elements are also discussed in this chapter. 

The exercise of this chapter comprises 40 questions. All of these questions have been designed to cover all the concepts taught in NCERT CBSE Class 12 Chemistry Chapter 7. The questions ask you to provide reasons, give explanations, provide preparation methods for the elements and compounds discussed in the chapter. Our NCERT Solutions answer all the questions of the exercise in detail with relevant examples and in a step by step manner.

The p-Block Elements precisely answers all of these questions, in an easy to understand language. Studying your CBSE NCERT Class 12 Chemistry Chapter 7 along with our strategically prepared NCERT Solutions for Class 12 Chemistry 7-The p-Block Elements will definitely help you excel in your Class 12 board exams.

NCERT Class 12 Chemistry Chapter 7: Important Topics

NCERT Solutions for Class 12 Chemistry Chapter 7 – The p-Block Elements includes all the concepts of this chapter. They give you complete knowledge of the subject matter. The main points covered explicitly in this chapter are as follows.

  • Group 15 Elements

This chapter tells you that group 15 includes nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb) and bismuth (Bi). These occur in the atmosphere, living beings and earth’s crust in different forms. 

Further, the chapter tells you that the general electronic configuration of group 15 elements is ns2np3. The elements show a gradation in properties while going down in the group. They generally react with oxygen, hydrogen and halogens. They exhibit two important oxidation states, + 3 and + 5 but, +3 oxidation is favoured by heavier elements due to ‘inert pair effect’.

This part further tells you that nitrogen behaves differently compared to other elements in the group because its size is small, it can form of pπ–pπ multiple bonds with itself and with highly electronegative atoms, and d orbitals are not available in nitrogen to expand its valence shell.

This chapter further discusses the preparation and properties of N2, NH3, oxides of nitrogen and nitric acid in detail. The oxides of nitrogen have resonating structures and have multiple bonds. It also discusses allotropic forms of P, white and red phosphorus, their preparation and properties along with discussing phosphine, phosphorus halides and oxoacids of phosphorus in detail. The oxoacids which have P–H bonds are good reducing agents and depending upon the number of P–OH groups their basicity varies.

  • Group 16 Elements

Here you learn that oxygen (O), sulphur (S), selenium (Se), tellurium (Te) and polonium (Po) constitute group 16 and have the general electronic configuration ns2np4. These elements can show a maximum of +6 oxidation state, though the other oxidation states shown by them are +2, +4 and +6. As in other groups, gradation in physical and chemical properties is observed.

This part of the chapter further tells you about the anomalous behaviour shown by oxygen which is a result of its high electronegativity value and small size. Also, the absence of d-orbitals limits its covalency to 2 practically and 4 theoretically. Further, you come to know that all the elements react with hydrogen to provide hydrides, with oxygen to form oxides and with halogens to form EX6, EX4 and EX2 in general. 

While discussing the individual elements, this chapter tells that O2 is prepared by heating KClO3 in the presence of MnO2 in the laboratory. Oxygen forms a number of oxides with metals. Allotropic form of oxygen is O3 which is a highly oxidising agent. Further, it tells that sulphur forms a number of allotropes, α– and β– forms being the most important ones. Sulphur and oxygen react with each other to give oxides such as SO2 and SO3. Sulphur dioxide is prepared by the reaction of sulphur with oxygen, and it is used in the manufacture of H2SO4. S forms a number of oxoacids, H2SO4 being the most important. It is prepared by the contact process and is used as a dehydrating and oxidising agent.

  • Group 17 Elements

In this part of the chapter, you learn that fluorine (F), chlorine (Cl), bromine (Br) and iodine (I) are the elements of group 17. Seawater is a major source of chlorides, bromides and iodides, and fluoride is present mainly as insoluble fluoride minerals. These elements have ns2np5 as their general electronic configuration.

The chapter further tells you that these elements have little tendency to lose electrons and the common oxidation state of these elements is –1. They can still show the highest oxidation state of +7. These elements are very reactive and are found in nature in a combined state only. The elements of this group show a regular gradation in physical and chemical properties. The common compounds they form are oxides, hydrogen halides, interhalogen compounds and oxoacids.

This part further tells you that F shows anomalous properties due to small size, more electronegativity and absence of d orbitals in it. Preparation and properties of Cl2, HCl have been discussed in detail in this portion. Further, you come to know that halogens combine with one another to form interhalogen compounds of the type XXʹn (n = 1, 3, 5, 7) where Xʹ is lighter than X. Halogens form a number of oxoacids where the halogen is in the centre, bonded in each case with one OH bond as X–OH, in some cases, X = O bonds are also found.

  • Group 18 Elements

This part of the chapter deals with the noble gases of group 18, helium (He), neon (Ne), Argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). Their electronic configuration is ns2 np6, and all the gases except Rn occur in the atmosphere. As they have complete octet as their outermost configuration, they have minimal tendency to react and form compounds. Compounds known at the most are those of xenon with fluorine and oxygen only under certain conditions. These gases have several uses in our day to day lives.

CBSE NCERT Class 12 Chemistry Chapter 7 Exercise-Discussion

Our NCERT Solutions for Class 12 Chemistry Chapter 7 – The p-Block Elements consists of 40 questions covering the important topics learnt here. The components of the exercise have been listed below.

  • Question 1 is an explanatory question based on general properties of group 15 elements. 
  • Questions 2 and 3 are based on the chemical reactivity of nitrogen.
  • Questions 4, 9 to 14 and 18 are reasoning based questions.
  • Questions 5 and 6 are based on the preparation of N2 and NH3.
  • Questions 7 and 8 are based on the reactivity of nitrogen compounds.
  • Questions 15, 16, and 31 are based on the reactivity of P and its compounds.
  • Questions 17 and 19 are justification questions.
  • Question 20 asks about ozone-depleting aerosols.
  • Questions 21 and 22 are based on S compounds.
  • Questions 23 to 29, 32 and 34 are based on the reactions and properties of halogens.
  • Questions 30, 33 and 35 are based on Xe compounds.
  • Question 36 asks you to arrange the given compounds in order of property indicated in the question.
  • Questions 37 and 38 are multiple-choice type questions.
  • Questions 39 and 40 are direct questions based on noble gases.

There are 34 intext questions asked in CBSE NCERT Class 12 Chemistry Chapter 7 to which accurate, detailed yet precise answers have been provided in our NCERT Solutions.

Benefits of NCERT Solutions for Class 12th Chemistry Chapter 7 – The p-Block Elements

The p-Block Elements is very helpful for you. Some of the advantages of reading from our NCERT Solutions are as follows –

  • They are written in an explanatory manner describing all the facts given in the chapter.
  • They have been prepared based on the latest CBSE Class 12 Chemistry Syllabus.
  • They are interactive and make the learning process efficient.
  • They provide important tips and techniques to solve the related questions. 
  • They are an excellent resource for learning and revising for your board exams and farewell in various competitive exams.