JNTU Pharm. D I Year PHARMACEUTICAL INORGANIC CHEMISTRY Previous Question Paper (January - 2022 - R08)

An error is defined as the difference between the measured value and the true or accepted value of a quantity. It represents the uncertainty inherent in any analytical measurement.

Errors are primarily classified into:

• Determinate (Systematic) Errors: These have a definite cause and can be identified and corrected. They include operational errors (e.g., loss of sample), instrumental errors (e.g., faulty balance), and method errors (e.g., improper indicator choice).
• Indeterminate (Random) Errors: These arise from uncontrollable variables such as slight fluctuations in temperature or human judgment during reading. They follow the laws of probability and cannot be entirely eliminated.
• Gross Errors: These result from human mistakes like misreading a scale or recording data incorrectly.

Methods to minimize errors:

1. Calibration: Regularly calibrating analytical instruments like burettes, pipettes, and balances against standard weights or known volumes ensures accuracy and eliminates instrumental systematic errors.
2. Blank Determinations: Performing a titration without the analyte under identical conditions helps identify and subtract errors caused by impurities in reagents or the indicator, thereby improving the accuracy of the final result.

Acid-base titrations are volumetric analytical procedures used to determine the concentration of an unknown acid or base by reacting it with a standard solution of a base or acid, respectively, until the equivalence point is reached, typically detected by a color change in an indicator.

The Lowry-Bronsted theory defines acids and bases based on proton (H+) transfer:

• Acid: A substance that acts as a proton donor.
• Base: A substance that acts as a proton acceptor.

According to this theory, every acid has a conjugate base, and every base has a conjugate acid. When an acid loses a proton, it forms its conjugate base, and when a base gains a proton, it forms its conjugate acid. The reaction is represented as:

This theory is broader than the Arrhenius theory because it explains acid-base behavior in non-aqueous solvents and identifies substances like ammonia as bases even in the absence of hydroxide ions.