The viva voce is a critical component of your practical exam. The examiner will ask you questions to assess your understanding of the experiments you performed. Marks are given for clear, confident, and correct answers.
What to Expect:
Questions will be based on:
The experiment you just performed:
"What was the principle of your experiment?"
"Why did you add [a specific reagent, e.g., dilute H2SO4 in potash alum prep]?"
"What is the reaction involved in your preparation?"
"What is the formula for [the compound you made, e.g., chrome alum]?"
"What is the principle of recrystallization?"
"Why is a 2,4-DNP derivative colored?"
"What is the working formula for viscosity/surface tension?"
"What is a transition temperature?"
Underlying Theory:
"What is Molarity? What is Normality?"
"What is the n-factor of KMnO4 in acidic medium?"
"What is a double salt? What is a complex?" (e.g., Potash alum vs Sodium Trisoxalatochromate)
"What is a bidentate ligand? Give an example." (e.g., oxalate)
"Why is the melting point of an impure solid lower and broader?"
"What is a reducing sugar? Why is sucrose non-reducing?" (Relates to organic section)
Apparatus and Techniques:
"What is this apparatus?" (e.g., Stalagmometer, Ostwald Viscometer)
"What is the purpose of calibration?"
"What precautions did you take while performing the experiment?"
How to Prepare for the Viva:
Understand, Don't Memorize: Don't just learn the procedure; understand *why* each step is done.
Know Your Notebook: Review every experiment in your lab notebook. The examiner may ask questions directly from it.
Be Honest: If you don't know an answer, it's better to say "I'm not sure, sir/ma'am" than to guess wildly.
Be Confident: Speak clearly. Your practical work proves you can *do* the experiment; the viva proves you *understand* it.
5. Regularity in maintenance of Lab Note Book
Your lab notebook (practical record) is the official log of all your work throughout the semester. It is a major component of your internal assessment.
What makes a good Lab Notebook?
Regularity & Completion: All experiments assigned during the semester must be present and signed by the instructor.
Neatness: It must be legible. Use a pen for records.
Structure: Every experiment should have a clear, consistent format:
Date
Title / Aim of the Experiment
Principle: A brief explanation of the theory.
Reaction: Chemical equations (for preparations).
Requirements: Apparatus and chemicals.
Procedure: Step-by-step account of what you *did*.
Observation / Observation Table: The raw data you collected (e.g., weights, time of flow, number of drops).
Calculation: Show all your work clearly.
Result: The final, clearly stated result (e.g., "The yield of chrome alum was 2.5 g", "The melting point of the derivative was 133-134°C", "The viscosity of the 10% solution was 1.05 cP").
Precautions: 2-3 key points to ensure a good result.
Originality: Data should be your own. Calculations must be shown.
For the Exam: Your notebook must be up-to-date, complete, and signed by your instructor. The external examiner will inspect it and base a significant portion of your marks on its quality and completeness.
6. Attendance
A significant portion of the internal assessment is based on your regularity in attending the practical classes. Chemistry practicals are hands-on, and skills can only be built through consistent practice.
Marks are often awarded based on the percentage of practical classes you have attended throughout the semester.
Missing classes means you have not performed those experiments, which will be reflected in your lab notebook and your ability to answer viva questions.