Most Frequently Asked 3 Marks Questions in STD 11 CBSE Chemistry Examinations

Chapter-wise Most Frequently Asked 3 Marks Questions in STD 11 Chemistry (NCERT)

1. Some Basic Concepts of Chemistry

• Explain the laws of chemical combination with suitable examples.
• Derive the relationship between molarity and molality.
• Calculate the empirical formula and molecular formula of a compound from given data.

2. Structure of Atom

• Derive the expression for energy of an electron in the hydrogen atom.
• Explain the quantum numbers and their significance.
• Write the differences between orbit and orbital.

3. Classification of Elements and Periodicity in Properties

• Discuss the trends in ionization energy across a period and down a group.
• Explain the modern periodic law.
• Write a short note on the anomalous behavior of some elements in the periodic table.

4. Chemical Bonding and Molecular Structure

• Explain the VSEPR theory with suitable examples.
• Differentiate between sigma and pi bonds.
• Explain the concept of hybridization with examples (e.g., sp, sp², sp³).

5. States of Matter

• Explain Boyle’s law and Charles’s law with graphs.
• Derive the ideal gas equation and explain the significance of the gas constant.
• Write a note on the liquefaction of gases (critical temperature and pressure).

6. Thermodynamics

• Derive the relationship between ∆H and ∆U.
• Explain the first law of thermodynamics and its mathematical expression.
• Write short notes on spontaneous and non-spontaneous processes.

7. Equilibrium

• Derive the relationship between Kp and Kc.
• Explain Le Chatelier’s principle with examples.
• Derive the expression for the dissociation constant of a weak acid.

8. The Redox Reactions

• Balance the following redox reaction in an acidic medium using the ion-electron method.
• Explain the concept of oxidation number with examples.
• Define redox reactions and differentiate between oxidation and reduction.

9. The Hydrogen

• Explain the isotopes of hydrogen and their significance.
• Write the preparation and properties of hydrogen peroxide.
• Explain the hydrides and their classification.

10. The s-Block Elements (Group 1 and Group 2 Elements)

• Write the general characteristics of alkali metals.
• Explain the diagonal relationship between lithium and magnesium.
• Discuss the biological importance of calcium and magnesium.

11. The p-Block Elements (Group 13 and Group 14 Elements)

• Discuss the anomalous behavior of boron.
• Explain the structure and bonding in diborane.
• Write a note on allotropes of carbon.

12. Organic Chemistry – Some Basic Principles and Techniques

• Explain inductive and resonance effects with examples.
• Write the IUPAC nomenclature rules with examples.
• Explain the methods of purification of organic compounds (e.g., distillation, crystallization).

13. Hydrocarbons

• Explain the reactions of alkanes (e.g., halogenation, combustion).
• Write the mechanism of electrophilic addition in alkenes.
• Explain the Markovnikov and anti-Markovnikov rules with examples.

14. Environmental Chemistry

• Discuss the causes and effects of air pollution.
• Explain the ozone layer and its depletion.
• Write a short note on greenhouse gases and their impact on global warming.

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