JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Pharmacy II Year PHARMACEUTICAL ANALYSIS-I Previous Question Paper (October/November-2020 - R17)
Answer any five questions. All questions carry equal marks.
Main
Explain the sources of errors. Write a note on types of errors. How are the errors minimized?
Answer
Errors in analytical chemistry represent the difference between the measured value and the true value of a quantity. They arise from various sources and are classified to ensure accuracy and precision in pharmaceutical analysis.
Sources of Errors:
- Personal Errors: Arise from the individual analyst due to lack of experience, poor judgment, or physical limitations such as color blindness or parallax errors during reading of burettes.
- Instrumental Errors: Caused by defects in measuring devices, such as uncalibrated weights, faulty glassware, or fluctuations in electrical supply for analytical instruments.
- Methodic Errors: Inherent to the analytical procedure, such as incomplete reactions, co-precipitation, or the presence of impurities in reagents.
- Additive and Proportional Errors: Additive errors are independent of the sample size, whereas proportional errors vary with the size of the sample.
Types of Errors:
- Determinate (Systematic) Errors: These have a definite cause and can be identified and corrected. They are unidirectional, meaning they consistently make results either higher or lower than the true value. Examples include calibration errors and constant reagent impurities.
- Indeterminate (Random) Errors: These are accidental and unpredictable, arising from uncontrollable variables in the environment or measurement process. They follow a Gaussian distribution and cannot be eliminated, but their effect can be minimized through statistical analysis.
- Gross Errors: These are large, obvious mistakes such as sample loss, misreading a scale by a large margin, or incorrect calculations. They usually result in outliers that must be discarded.
Minimization of Errors:
- Calibration: Regularly calibrate all analytical instruments, weights, and glassware against standard references.
- Standardization: Use high-purity reagents and standardize titrants frequently.
- Control Experiments: Perform blank determinations to account for impurities in reagents and solvents.
- Replicate Analysis: Perform multiple measurements (at least 3-5) to calculate the mean and standard deviation, which helps in identifying and rejecting outliers.
- Standard Addition Method: Use this technique to account for matrix effects in complex samples.
- Training: Ensure rigorous training of personnel to minimize personal bias and improve technical proficiency.
Describe the preparation and standardization of potassium permanganate.
Answer
Potassium permanganate (KMnO4) is not a primary standard because it often contains traces of manganese dioxide and organic impurities. Therefore, it must be prepared and standardized before use in redox titrations.
Preparation: Dissolve approximately 3.2 g of KMnO4 in 1 liter of distilled water. Boil the solution for 15-30 minutes to oxidize any organic matter present in the water. Allow the solution to cool and stand for 24 hours. Filter the solution through a sintered glass crucible or glass wool to remove the precipitated manganese dioxide (MnO2), which catalyzes the decomposition of the permanganate. Store the solution in an amber-colored glass bottle to protect it from light.
Standardization: The solution is typically standardized against sodium oxalate (Na2C2O4), a primary standard. The reaction is: 2MnO4- + 5C2O42- + 16H+ → 2Mn2+ + 10CO2 + 8H2O. Weigh accurately about 0.2 g of dried sodium oxalate, dissolve it in 250 mL of dilute sulfuric acid, and heat the mixture to 70-80°C. Titrate with the KMnO4 solution until a faint permanent pink color appears. The reaction is self-indicating.
Write a note on significant figures, accuracy and precision.
Answer
Sign in to view the complete answer paper.
Explain the theory of strong acid against strong base along with its titration curve.
Answer
Sign in to view the complete answer paper.
Write the principle involved in NAT.
Answer
Sign in to view the complete answer paper.
Classify various solvents used in non-aqueous titrations.
Answer
Sign in to view the complete answer paper.
Explain any one procedure of non-aqueous titration of a weak base with an example.
Answer
Sign in to view the complete answer paper.
Explain the various steps involved in gravimetric analysis, indicating the importance and precautions to be taken in each step. Write briefly about co-precipitation.
Answer
Sign in to view the complete answer paper.
Explain the principle of precipitation titrations. Write a brief note on metal ion indicators.
Answer
Sign in to view the complete answer paper.
Differentiate the types of precipitation titrations. Explain any one type.
Answer
Sign in to view the complete answer paper.
Explain different types of redox titrations with examples.
Answer
Sign in to view the complete answer paper.
Explain the principle involved in the assay of ferrous sulphate using cerimetry.
Answer
Sign in to view the complete answer paper.
Write the principle and applications of Dead stop end point technique.
Answer
Sign in to view the complete answer paper.
Write the advantages and disadvantages of Conductometric titrations.
Answer
Sign in to view the complete answer paper.