Of course! Here is a comprehensive list of potential viva questions with short, simple answers designed to cover your entire syllabus and help you score full marks. I've organized them by topic for easy revision.
### **1. Atomic Structure and Periodicity**
**Rutherford's Model & Limitations**
1. **What did Rutherford's gold foil experiment conclude?**
* The atom has a small, dense, positively charged nucleus with electrons moving around it.
2. **What are the limitations of Rutherford's model?**
* It couldn't explain the stability of the atom (why electrons don't spiral into the nucleus) and the discrete line spectra of elements.
**Quantum Mechanics**
3. **What is Planck's quantum hypothesis?**
* Energy is emitted or absorbed in discrete packets called "quanta" (photons), not continuously. E = hν.
4. **Explain the photoelectric effect.**
* When light of a certain frequency (threshold frequency) shines on a metal surface, it ejects electrons.
5. **What did Bohr propose for the hydrogen atom?**
* Electrons revolve in fixed, stable orbits without radiating energy. They only absorb/emit energy when jumping between these orbits.
6. **What are the limitations of Bohr's theory?**
* It failed for multi-electron atoms and couldn't explain the fine structure of spectral lines or the Zeeman effect.
7. **What is de Broglie's concept of matter waves?**
* All moving particles have a wave nature associated with them. Wavelength (λ) = h / p (momentum).
8. **State Heisenberg's Uncertainty Principle.**
* It is impossible to simultaneously determine the exact position and exact momentum of a subatomic particle. Δx * Δp ≥ h/4π.
**Periodic Table & Trends**
9. **How are elements classified as s, p, d, or f-block?**
* Based on the subshell (s, p, d, f) in which the last electron enters.
10. **Define atomic radius.**
* It is the distance from the nucleus to the outermost shell of electrons.
11. **What is the trend of atomic radius across a period?**
* It decreases due to an increase in effective nuclear charge.
12. **What is ionization energy?**
* The minimum energy required to remove the most loosely bound electron from an isolated gaseous atom.
13. **What is the trend of ionization energy down a group?**
* It decreases because atomic size increases and the outer electron is less tightly held.
14. **What is electronegativity?**
* The tendency of an atom to attract the shared pair of electrons in a covalent bond.
15. **Define electron gain enthalpy.**
* The energy change when an electron is added to a neutral gaseous atom.
16. **What is effective nuclear charge (Zeff)?**
* The net positive charge experienced by an electron in an atom. Zeff = Z (atomic number) - S (screening constant).
---
### **2. Chemical Bonding**
**Bond Types**
17. **What is an ionic bond?**
* A bond formed by the complete transfer of electrons from one atom to another, creating oppositely charged ions.
18. **What is lattice energy?**
* The energy released when one mole of an ionic crystal is formed from its gaseous ions.
19. **What is a covalent bond?**
* A bond formed by the mutual sharing of electrons between two atoms.
20. **What is a co-ordinate (dative) bond?**
* A covalent bond where both electrons are contributed by a single atom.
**Hybridization & VSEPR**
21. **What is hybridization?**
* The mixing of atomic orbitals of similar energy to form new hybrid orbitals of equal energy.
22. **What is the shape and hybridization of:**
* **Methane (CH₄)?** Tetrahedral, sp³
* **Ethene (C₂H₄)?** Planar, sp²
* **Ethyne (C₂H₂)?** Linear, sp
* **BF₃?** Trigonal planar, sp²
* **NH₃?** Pyramidal, sp³
* **H₂O?** Bent/V-shaped, sp³
* **PCl₅?** Trigonal bipyramidal, sp³d
* **SF₆?** Octahedral, sp³d²
23. **What does VSEPR theory stand for and what does it state?**
* Valence Shell Electron Pair Repulsion. It states that electron pairs around a central atom repel each other and arrange themselves to be as far apart as possible.
**Molecular Orbital (MO) Theory**
24. **How does MO theory explain the bonding in O₂?**
* MO theory correctly predicts O₂ is paramagnetic (has unpaired electrons), which Valence Bond theory could not.
---
### **3. Basics of Analytical Chemistry**
**Basic Concepts**
25. **Define a mole.**
* The amount of substance containing the same number of entities (atoms, molecules) as there are in 12g of Carbon-12. (6.022 x 10²³ entities).
26. **What is the difference between molarity and molality?**
* **Molarity (M):** Moles of solute per liter of *solution*.
* **Molality (m):** Moles of solute per kilogram of *solvent*.
27. **What is normality?**
* Number of gram equivalents of solute per liter of solution.
28. **What is a primary standard?**
* A highly pure, stable compound used to prepare a standard solution of known concentration directly (e.g., Oxalic acid, K₂Cr₂O₇).
29. **What is a secondary standard?**
* A solution whose concentration is determined by titrating it against a primary standard (e.g., NaOH solution).
**Titrations**
30. **What is the function of an indicator in acid-base titration?**
* To show the endpoint by a sharp change in color at a specific pH.
31. **Give an example of a redox indicator.**
* Diphenylamine.
32. **What is the role of KMnO₄ in redox titrations?**
* It acts as a self-indicator (oxidizing agent).
33. **What is complexometric titration?**
* A titration involving the formation of a complex between the metal ion and a ligand (like EDTA).
---
### **4. Nuclear Chemistry**
**Basic Concepts**
34. **What are isotopes?**
* Atoms of the same element with the same atomic number but different mass numbers (same protons, different neutrons).
35. **What are isobars?**
* Atoms of different elements with the same mass number but different atomic numbers.
36. **What is the n/p ratio?**
* The ratio of neutrons to protons in a nucleus, which determines its stability.
37. **What is the Liquid Drop Model?**
* A model that treats the nucleus as a drop of incompressible liquid to explain nuclear fission.
**Radioactivity**
38. **Define half-life of a radioactive element.**
* The time taken for half of the radioactive atoms in a sample to decay.
39. **What is the Group Displacement Law?**
* When an atom emits an alpha particle, it moves two places left in the periodic table. When it emits a beta particle, it moves one place right.
40. **What is radiocarbon dating?**
* A method to determine the age of ancient carbonaceous materials by measuring the decay of Carbon-14.
**Nuclear Energy**
41. **What is the difference between nuclear fission and fusion?**
* **Fission:** A heavy nucleus splits into lighter nuclei (e.g., in nuclear reactors).
* **Fusion:** Two light nuclei combine to form a heavier nucleus (e.g., in the sun).
42. **What is mass defect?**
* The difference between the calculated mass of a nucleus (sum of protons and neutrons) and its actual measured mass.
43. **What is nuclear binding energy?**
* The energy equivalent to the mass defect, released when a nucleus is formed. It is a measure of the stability of the nucleus.
**Final Tips for the Viva:**
* **Be Confident:** Speak clearly and confidently.
* **Listen Carefully:** Make sure you understand the question before answering.
* **Keep it Simple:** The examiner wants to know you understand the concept, not a memorized paragraph.
* **If You Don't Know:** It's okay to say "I'm not sure, but I think it might be related to..." rather than guessing wildly.
Good luck with your viva! You've got this