Determination of pKa Using a pH Meter

1. Aim

To complete the Year 3 practical determination of pka using a ph meter using a verified method, demonstration, or supplied dataset. The actual sample and finding must be entered in the student record.

2. Requirements

Instructor-approved sample or de-identified instrument record, reference standards, blanks and quality controls, method sheet, calibration record, observation form, calculator or plotting tool, protective equipment, and waste procedure. Exact reagents, volumes, concentrations, settings, and limits are specified in your college lab manual and instructor's method sheet.

3. Theory

For a suitable weak acid-base system, pH at the half-neutralization point can equal pKa under the relevant assumptions. Electrode calibration, temperature, ionic strength, and accurate equivalence volume matter. A pH curve must support a clear half-equivalence point; one isolated pH reading cannot determine pKa.

4. Procedure

Identify the syllabus entry, sample or dataset, method revision, instrument calibration, and hazards.
Record reference, blank, control, and sample measurements with units and source IDs.
Observe the approved method or analyze the supplied dataset without filling missing conditions by guesswork.
Review the validated titration curve and pH meter calibration. Locate equivalence volume, take half that volume, read its pH, and state the method assumptions.
Check method suitability, range, and control behaviour before any calculation or interpretation.
Report raw observations, the justified calculation, limitations, and your college lab manual and instructor's method sheet items separately.

5. Observation and calculation

Student record field	Entry
Case or product	Record here
Method	Record here
Observation	Record here
Inference	Record here
Supervisor check	Record here
Outcome	Record here

Assumed values for practice only: Assumed equivalence volume is 20.0 mL and assumed pH at assumed 10.0 mL is 4.8. The illustrative pKa is assumed 4.8 for a suitable monoprotic system, not an actual compound value. Every invented input and output is assumed, not a real analytical result or operating instruction.

6. Output or final result

Provide a labelled half-equivalence pH plot and conditional interpretation. Record the supervised outcome here.

Teaching-lab safety: Perform chemical or instrument work only under instructor supervision with the approved safety and waste procedures. Assumed values are examples only.

This page is a supervised-activity guide; it does not report a completed case.

7. Sources

← Determination of Sodium and Potassium by Flame PhotometryDetermination of Specific Rotation →

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