50 Most important questions For Board Exam Chemistry

 सरस्वती वंदना सरस्वती वंदना 

Maa Sherawli ka Esa Bhajan Jisko Sunkar Bhagye Chamak Jaayega 

Based on the latest CBSE Class 12 Chemistry syllabus for the academic year 2024-25, here are 50 important questions for last-minute revision, each accompanied by a concise answer:

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Unit I: Solutions

1. Define molality.

   • Moles of solute per kilogram of solvent.

2. State Raoult's Law for ideal solutions.

   • The partial vapor pressure of each volatile component in a solution is directly proportional to its mole fraction.

3. What is the Van't Hoff factor (i) for K₄[Fe(CN)₆]?

   • 5

4. Name the colligative property used to determine molar mass from the depression in freezing point.

   • Cryoscopy

5. What causes an elevation in boiling point?

   • Addition of a non-volatile solute to a solvent.

Unit II: Electrochemistry

6. What is the standard electrode potential of a standard hydrogen electrode (SHE)?

   • 0 volts

7. Write the Nernst equation for a cell reaction.

   • E = E° - (RT/nF) lnQ

8. Define molar conductivity.

   • Conductivity of an electrolyte solution divided by its molar concentration.

9. What is the primary electrolyte in a lead-acid battery?

   • Sulfuric acid (H₂SO₄)

10. Name a fuel cell used in spacecraft.

    • Hydrogen-oxygen fuel cell

Unit III: Chemical Kinetics

11. Define the rate of a chemical reaction.

    • Change in concentration of reactants or products per unit time.

12. What is the unit of the rate constant for a first-order reaction?

    • s⁻¹

13. State the Arrhenius equation.

    • k = A e^(-Ea/RT)

14. What does the slope represent in an Arrhenius plot?

    • -Ea/R (negative activation energy over the gas constant)

15. Define activation energy.

    • Minimum energy required for reactants to form products.

Unit IV: d- and f-Block Elements

16. Which element is known as the 'transition metal' with the highest melting point?

    • Tungsten (W)

17. What is lanthanoid contraction?

    • Gradual decrease in the size of lanthanoid ions with increasing atomic number.

18. Name the ore from which potassium dichromate is prepared.

    • Chromite (FeCr₂O₄)

19. What is the common oxidation state of actinoids?

    • +3

20. Which transition metal is used in the manufacture of stainless steel?

    • Chromium (Cr)

Unit V: Coordination Compounds

21. Define a ligand.

    • An ion or molecule that donates a pair of electrons to a central metal atom/ion.

22. What is the coordination number of [Fe(CN)₆]³⁻?

    • 6

23. Name the type of isomerism exhibited by [Co(NH₃)₄Cl₂]⁺.

    • Geometrical isomerism

24. What is the oxidation state of platinum in [PtCl₂(NH₃)₂]?

    • +2

25. State Werner's theory in coordination chemistry.

    • It distinguishes between primary (ionizable) and secondary (non-ionizable) valencies of metals.

Unit VI: Haloalkanes and Haloarenes

26. What is the IUPAC name of CH₃-CH₂-Br?

    • Bromoethane

27. Which halogen compound is known as chloroform?

    • Trichloromethane (CHCl₃)

28. What is the major product of chlorination of benzene?

    • Chlorobenzene

29. Name the effect responsible for the deactivating nature of halogens in electrophilic substitution reactions.

    • -I (negative inductive) effect

30. Which environmental pollutant is known as Freon-12?

    • Dichlorodifluoromethane (CCl₂F₂)

Unit VII: Alcohols, Phenols, and Ethers

31. What is the common name of methanol?

    • Wood alcohol

32. Name the process used for the industrial preparation of ethanol.

    • Fermentation

33. What is the IUPAC name of phenol?

    • Benzenol

34. Which reagent is used to oxidize primary alcohols to aldehydes?

    • Pyridinium chlorochromate (PCC)

35. Name the product formed when phenol reacts with bromine water.

    • 2,4,6-Tribromophenol

Unit VIII: Aldehydes, Ketones, and Carboxylic Acids

36. What is the functional group of aldehydes?

    • -CHO

37. Name the simplest ketone.

    • **Acetone