Essential Questions for CBSE Class 12 Chemistry Case Studies, Accompanied by Solutions, available for Download as a PDF File

In preparation for the upcoming CBSE Class 12 Chemistry exam, here's a rundown of some key topics and guidelines that you might find useful.

The exam will consist of five sections: Section A with 16 multiple-choice questions, Section B with 5 short-answer questions, Section C with 7 short-answer questions, Section D with 2 case study-based questions, and Section E with 3 long-answer questions. All questions are compulsory, and the use of log tables and calculators is not allowed.

One of the topics that will be covered is the structure of DNA. Did you know that a single helix DNA virus has a genetic material that is composed of 20% adenine, 20% thymine, 20% guanine, and the rest cytosine? This unique composition is fascinating, as it contributes to the structure and function of the virus.

Another important topic is the reaction between hydrogen gas and bromine. The currently accepted mechanism for this reaction involves the dissociation of bromine molecules into atoms, followed by reactions between atoms and molecules. The rate of this reaction is proportional to the concentration of H2 and to the square root of the concentration of Br2. However, the reaction is inhibited by increasing the concentration of HBr as the reaction proceeds.

In the realm of inorganic chemistry, the packing of oppositely charged spheres of different radii plays a crucial role in determining the structure of crystals. Linus Pauling proposed the first guidelines for guessing the coordination numbers and bonding geometries of atoms in crystals based on these geometric considerations. His guidelines do not consider the specific chemical properties of the cations and anions.

The quality of the "fit" between the cation and anion in a crystal structure depends on the radius ratio of the anion and the cation. Cations will find arrangements in which they can contact the largest number of anions, and if the anion is considered as the packing atom in the crystal, the smaller cation fills interstitial sites ("holes"). If the cation can touch all of its nearest neighbour anions, the fit is good.

Chargaff's rule states that the total amount of purines (A + G) and the total amount of pyrimidines (C + T) are usually nearly equal in DNA. This rule is a fundamental principle in understanding the structure and composition of DNA.

Lastly, the capacitors developed by Linus Pauling, known as Pauling capacitors, have facilitated crystallographers in solving the structures of inorganic solids using X-ray diffraction. Additionally, scientists can determine if samples belong to the same species by studying the nucleotide composition of DNA.

Preparing for the exam? Remember to revise these topics and guidelines to ensure a successful examination experience!

Essential Questions for CBSE Class 12 Chemistry Case Studies, Accompanied by Solutions, available for Download as a PDF File