| target | 30/30 |
| author | Senior Sibling |
| name | lab-practical |
| description | 12th Grade 30-mark Practical Exams (PCMB/PCMC). Covers Volumetric Analysis, Salt Analysis, Physics Experiments, and Viva strategy. |
Lab Practical & Viva — Securing the 30/30
In Grade 12, the Practical exam is 30 Marks. It is evaluated by an External Examiner. You need a perfect Lab Record, a functional project, and a confident Viva performance.
🧪 Chemistry Experiments (30M)
1. Volumetric Analysis (8 Marks)
- Experiment: Determination of concentration/molarity of $KMnO_4$ solution by titrating it against a standard solution of Oxalic Acid or Ferrous Ammonium Sulphate (Mohr's Salt).
- Viva Logic:
- Why is $H_2SO_4$ added? (To provide acidic medium and prevent $MnO_2$ precipitation).
- Why don't we use $HCl$ or $HNO_3$? ($HCl$ is oxidized by $KMnO_4$, $HNO_3$ is itself an oxidizing agent).
- What is the indicator? ($KMnO_4$ is a self-indicator).
2. Salt Analysis (8 Marks)
- Experiment: Identification of one Cation and one Anion in a given salt.
- Anions: Carbonate, Sulphide, Sulphite, Nitrite, Sulphate, Chloride, Bromide, Iodide, Nitrate, Oxalate, Acetate, Phosphate.
- Cations: $Pb^{2+}, Cu^{2+}, As^{3+}, Al^{3+}, Fe^{3+}, Mn^{2+}, Zn^{2+}, Ni^{2+}, Co^{2+}, Ca^{2+}, Sr^{2+}, Ba^{2+}, Mg^{2+}, NH_4^+$.
- Viva Logic: Confirmatory tests (e.g., Brown Ring test for Nitrate, Chromyl Chloride test for Chloride).
🔭 Physics Experiments (30M)
1. Section A & B Experiments
- Current Electricity: Ohm's Law (12th depth), Meter Bridge (Finding resistance/specific resistance), Potentiometer (Comparing EMF or finding Internal Resistance).
- Optics: Focal length of Convex Lens/Mirror using $u-v$ method, Refractive index of a glass slab/liquid using Traveling Microscope.
- Semiconductors: V-I characteristics of P-N junction diode and Zener diode.
2. Viva Strategy
- Meter Bridge: Why should the balance point be in the middle ($40-60 cm$)? (For maximum sensitivity).
- Potentiometer: Why is it preferred over a voltmeter? (It draws no current at null point, giving true EMF).
🧬 Biology Experiments (30M)
- Spotting: Identification of slides/models (e.g., T.S. of Testis/Ovary, Meiosis stages, Blastula stage).
- Major Experiment: Isolation of DNA from plant material (e.g., Spinach/Pea).
- Minor Experiment: Study of pollen germination on a slide.
✍️ The "Senior Sibling" Viva Protocol
- Appearance: Wear a clean lab coat. Keep your hair tied/neat.
- The First Question: Most examiners ask "What is your favorite chapter?". Always have one chapter (e.g., Electrostatics or Coordination Compounds) mastered deeply for this.
- Honesty: If you don't know an answer, say "I am unable to recall at the moment, sir/ma'am" instead of guessing wildly.
Command Integration: Use /viva-bot [Subject] to simulate a mock viva session with an external examiner persona.
