Pharmaceutics Laboratory
Calculate the mass of solute for a stated concentration, weigh it on an analytical balance, dissolve and transfer it quantitatively to a volumetric flask, make up to the mark, then prepare an accurate dilution with a bulb pipette — and verify both concentrations.
A solution's strength can be stated in several measures: % w/v is grams per 100 mL, mg/mL is milligrams per millilitre, and mol/L is moles of solute per litre (mass ÷ Mr ÷ volume in litres). Read which one the task uses before you calculate.
A standard solution is made by weighing the solute accurately, dissolving it completely in part of the solvent, transferring it QUANTITATIVELY to a volumetric flask — rinsing everything it touched into the flask — and making up to the mark at eye level, then mixing by inversion.
A dilution follows C₁V₁ = C₂V₂: the amount of solute in the aliquot (C₁V₁) is the amount in the diluted solution (C₂V₂). A 1 in 10 dilution takes 10.00 mL of stock to 100.0 mL.
Class A glassware sets the precision: a 100 mL volumetric flask ±0.08 mL, a 10 mL bulb pipette ±0.02 mL, but a 100 mL measuring cylinder only about ±0.5–1 mL.
Report what you made, not what you aimed for: the concentration comes from the mass you recorded and the volumes of the glassware you used.
Teaching values: the task strengths, the ±2 % weighing tolerance and the transfer-loss figures are this lab's teaching values. 0.900 % w/v is the strength of normal saline, but this is a practice solution — never for use.
Sodium chloride (NaCl) · Purified water
Curriculum
Listed in the UoK Pharm-D practical syllabus (PHT-502 Physical Pharmacy (Lab), 3rd year, 2nd semester: “preparation of stock solution (dilution method)”) and in HEC Physical Pharmacy I (Semester I: “Preparation of Solutions, Dilutions”). The solutes and strengths used here are our illustrative choice. Not faculty-reviewed.
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Simulated practice: results come from teaching models and illustrative data described on this page. Nothing you enter is sent anywhere unless you are signed in, in which case your completion is added to your progress.
