An Overview of Ncert Books Class 12 Chemistry Chapter 9 Free Download
FAQs on Ncert Books Class 12 Chemistry Chapter 9 Free Download
1. What are the most important topics in Coordination Compounds for the CBSE Class 12 Chemistry board exam 2025-26?
For the CBSE Class 12 board exam, the most crucial topics from Coordination Compounds that are frequently tested include:
- IUPAC Nomenclature: Writing the name from the formula and vice versa.
- Isomerism: Especially structural (linkage, coordination) and stereoisomerism (geometrical, optical).
- Valence Bond Theory (VBT): Predicting hybridisation, geometry, and magnetic properties of complexes.
- Crystal Field Theory (CFT): Explaining d-orbital splitting in octahedral and tetrahedral complexes, colour, and magnetic properties.
- Werner's Theory: Understanding primary and secondary valencies.
2. What is the expected marks distribution and question pattern for Coordination Compounds in the board exam?
Coordination Compounds is a high-weightage chapter, typically accounting for around 7 marks. For the 2025-26 exam, expect a mix of question types:
- MCQs (1-mark): Focused on definitions, IUPAC names of simple complexes, or identifying the type of isomerism.
- Short Answer Questions (2 or 3-marks): Problems based on VBT to find hybridisation, questions on distinguishing between isomers, or explaining concepts from CFT.
- Long Answer/Case-Based Questions (4 or 5-marks): These often integrate multiple concepts, such as using VBT and CFT to explain the structure and properties (colour, magnetism) of a given complex, or detailed questions on stereoisomerism.
3. Which specific types of isomerism questions are most expected in the Class 12 Chemistry exam?
In board exams, questions on isomerism are very common. You should focus on:
- Geometrical Isomerism: Differentiating between cis and trans isomers, especially in square planar complexes like [Pt(NH₃)₂(Cl)₂] and octahedral complexes like [Co(NH₃)₄Cl₂]⁺.
- Optical Isomerism: Identifying chiral complexes that can show optical activity. The most classic example is the octahedral complex [Co(en)₃]³⁺.
- Linkage Isomerism: Questions involving ambidentate ligands like NO₂⁻ and SCN⁻ are frequently asked to test identification of this isomerism.
4. What are the most important questions related to Valence Bond Theory (VBT) and Crystal Field Theory (CFT)?
From VBT and CFT, the most important questions involve their application.
- From VBT: You will be asked to determine the hybridisation (e.g., sp³, d²sp³, sp³d²), shape (tetrahedral, square planar, octahedral), and magnetic character (paramagnetic or diamagnetic) of a given coordination entity like [Ni(CO)₄] or [CoF₆]³⁻.
- From CFT: Important questions include drawing the d-orbital splitting diagrams for octahedral and tetrahedral complexes, explaining why certain complexes are coloured while others are not, and arranging complexes in order of their crystal field splitting energy (CFSE).
5. Why is Crystal Field Theory (CFT) considered an improvement over Valence Bond Theory (VBT) for exam-level explanations?
CFT provides a better explanation for several properties of coordination compounds where VBT falls short, which is a key area for HOTS (Higher Order Thinking Skills) questions. The main advantages of CFT are:
- It provides a basis for explaining the colours of coordination compounds, which VBT cannot.
- It gives a quantitative measure of the stability of a complex through Crystal Field Stabilisation Energy (CFSE).
- It provides a clearer distinction and reasoning for the formation of inner orbital (low spin) vs. outer orbital (high spin) complexes based on the nature of the ligand and the metal ion.
6. What is a common mistake students make when applying VBT to determine a complex's properties, and how can it be avoided?
A very common mistake is the incorrect identification of a ligand as strong-field or weak-field. This directly leads to errors in determining electron pairing, hybridisation, and magnetic moment. For example, in [Co(NH₃)₆]³⁺, ammonia (NH₃) acts as a strong-field ligand, forcing electron pairing and resulting in d²sp³ hybridisation (inner orbital, diamagnetic). In contrast, in [CoF₆]³⁻, fluoride (F⁻) is a weak-field ligand, leading to no pairing and sp³d² hybridisation (outer orbital, paramagnetic). To avoid this, memorise the spectrochemical series as per the NCERT syllabus to correctly classify ligands.
7. How are questions on the stability of coordination compounds framed in exams, particularly concerning the chelate effect?
Questions on stability often test the concept of the chelate effect. You might be asked to compare the stability of two complexes, one with monodentate ligands and another with a bidentate or polydentate ligand. For example, a question might ask why [Co(en)₃]³⁺ is more stable than [Co(NH₃)₆]³⁺. The answer lies in the chelate effect: ethylenediamine (en) is a bidentate ligand that forms stable five-membered rings with the central metal ion, increasing the overall stability of the complex. This enhanced stability of complexes with polydentate ligands is known as the chelate effect.
8. Are questions on the applications of coordination compounds important for the board exam?
Yes, questions on the applications of coordination compounds can be asked, typically as 1-mark questions or as part of a larger problem. It is important to know key applications such as:
- The role of EDTA in estimating the hardness of water and in treating lead poisoning.
- The use of cis-platin as an anti-cancer drug.
- The importance of complexes in biological systems, like haemoglobin (iron complex) for oxygen transport and chlorophyll (magnesium complex) for photosynthesis.
