PCT 202 is the paper where the physical chemistry behind medicines finally has a number attached to it. As a 200 Level Pharmacy student at ABUAD, you are expected to explain why a drug dissolves, predict how a solution behaves, read a phase diagram, and then push a formula through a dilution or alligation calculation without dropping a decimal place. That mix of theory and arithmetic is exactly why students find PCT 202 – Pharmaceutical Preparations & Calculations harder than it looks on the timetable.
This EverythingABUAD guide takes the second-semester syllabus and lays it out in plain language, topic by topic, so you can see where the marks actually sit. We explain the reasoning first, then let you test yourself on original practice questions with fully worked answers, including the tricky calculation items where most people lose easy points. The complete workbook is embedded in the interactive reader further down the page, free to read online or download for offline revision.
- Course: PCT 202 – Pharmaceutical Preparations & Calculations
- College / Department: College of Pharmacy / Pharmacy
- Level / Semester: 200 Level, Second Semester
- Topics covered: Solutions, Solvents & Vehicles; Solubility & Co-solvency; Partition & Nernst's Law; Colligative Properties; The Phase Rule & Freeze Drying; Dosage Forms; and Pharmaceutical Calculations & Tonicity
- Best for: Continuous assessment + final exam revision
Topics Covered in PCT 202
1. Pharmaceutical Solutions, Solvents & Vehicles
This opening block is about matching a drug to the right liquid. You need to know why water is the chief vehicle for water-soluble actives, why alcohol is the go-to solvent for many organic drugs, and why a clear hydro-alcoholic elixir can dissolve substances that a plain aqueous syrup cannot. You also learn the safety line between solvents: glycerol and propylene glycol are fine internally, but ethylene glycol is toxic and stays out of oral products. Exam tip: lock down the miscibility facts early, especially that glycerol mixes with both water and alcohol yet stays immiscible with fixed oils, because examiners test those true/false traps every year.
2. Solubility, Dissolution & Co-solvency
Here you move from what dissolves to how much and why. Solubility depends on temperature, the solute and the solvent together, and the direction it moves with heat depends on whether dissolution absorbs or releases energy. Co-solvency is the practical trick worth remembering: blending water with ethanol, propylene glycol or glycerin can raise a stubborn drug's solubility several-fold, which is exactly how poorly soluble actives like metronidazole are handled. Exam tip: keep the endothermic-versus-exothermic rule straight, since an endothermic dissolution gains solubility with heat while an exothermic one loses it, and that single distinction decides a cluster of true/false marks.
3. Partition & Nernst's Distribution Law
When a solute is shaken between two immiscible liquids, it splits between them in a fixed ratio at equilibrium, and that ratio is the partition coefficient. This one idea explains solvent extraction of drugs and plant actives, how a preservative distributes between the oil and water phases of an emulsion, and how a drug crosses biological membranes. Exam tip: remember the extraction rule that examiners love, which is that several small portions of extracting solvent recover far more compound than a single large portion, and be ready to list four or five pharmaceutical applications of the law.
4. Colligative Properties & Vapour Pressure
Colligative properties depend on the number of dissolved particles, not their chemical identity. Add a non-volatile solute and the solvent's vapour pressure falls, while boiling point, osmotic pressure and freezing-point depression all shift in step. Raoult's law ties the drop in vapour pressure to the mole fraction of solvent, and these calculations show up as full worked questions rather than true/false. Exam tip: practise the vapour-pressure sum in moles, not grams, because the relative lowering equals the mole fraction of the solute, and getting the moles right is the whole battle in that calculation.
5. The Phase Rule, Equilibrium & Freeze Drying
The Gibbs phase rule, F = C − P + 2, lets you count how many variables you can change while the phases of a system survive. For pure water, three coexisting phases give F = 0, the invariant triple point; two phases leave one degree of freedom. This links directly to freeze drying, where a frozen product is held below the triple point so ice sublimes straight to vapour under vacuum. Exam tip: memorise the phase-rule equation and rehearse plugging numbers into it for one- and two-component systems, then connect the triple point to the sublimation step of lyophilisation, since the two topics are often examined together.
6. Dosage Forms & Pharmaceutical Calculations
The final block is the heaviest for marks. On the theory side you separate diffusible from indiffusible suspensions, rank capsule sizes (000 largest to 5 smallest), and know why most tablets are made by compression and why granulation improves flow and compressibility. On the numbers side you handle ratio strength, C₁V₁ = C₂V₂ dilutions, alligation, specific gravity and tonicity. Exam tip: treat accuracy as a patient-safety issue, write out every dilution with units attached, and drill the conversion between percentage strength and "1 in X" both ways until it is automatic under exam pressure.
Sample Practice Questions (With Answers)
A few sample items below, written in our own words, with the reasoning laid out so you follow the why and not just the final figure:
Q1. A sweetening solution at 27 °C holds 90.1 g of fructose (M = 180.2) in 500 g of water (M = 18.02). Pure water's vapour pressure at 27 °C is 18.535 mmHg. Find the relative lowering of vapour pressure, the actual lowering, and the vapour pressure of the solution.
Answer: Work in moles. Fructose = 90.1 ÷ 180.2 = 0.500 mol; water = 500 ÷ 18.02 = 27.75 mol. Relative lowering = mole fraction of solute = 0.500 ÷ (0.500 + 27.75) = 0.500 ÷ 28.25 = 0.0177. Lowering Δp = 0.0177 × 18.535 = 0.328 mmHg. Vapour pressure of the solution = 18.535 − 0.328 = 18.207 mmHg.
Q2. You dilute 400 mL of a 20% w/v solution up to 2 L. What is the final percentage strength?
Answer: Use C₁V₁ = C₂V₂. So 20% × 400 mL = C₂ × 2000 mL, giving C₂ = 8000 ÷ 2000 = 4% w/v. The amount of solute never changes on dilution; only the volume grows, so a five-fold increase in volume cuts the strength five-fold.
Q3. Rx: benzalkonium chloride solution, 240 mL, made so that 10 mL diluted to one litre gives a 1:5000 w/v solution. How many litres of a 16% w/v stock are needed?
Answer: One litre of the 1:5000 final dilution contains 0.2 g, and that 0.2 g comes from the 10 mL drawn off your preparation, so the 240 mL preparation must be 0.2 g/10 mL = 2% w/v. Total benzalkonium needed = 240 × 0.02 = 4.8 g. From a 16% stock (0.16 g/mL), volume = 4.8 ÷ 0.16 = 30 mL = 0.03 L.
Q4. Applying the Gibbs phase rule to pure water, what is the degree of freedom when solid, liquid and vapour all coexist, and what is that condition called?
Answer: For a one-component system, F = C − P + 2 = 1 − 3 + 2 = 0. Zero degrees of freedom means the system is invariant, fixed at one exact temperature and pressure. That unique point where all three phases coexist is the triple point.
Q5. A red blood cell is placed in a hypertonic solution. What happens to it, and how does this differ from hypotonic and isotonic media?
Answer: A hypertonic solution has a higher solute concentration than the cell, so water leaves the cell and it shrinks (crenation). A hypotonic solution is more dilute than the cell, so water enters and the cell swells and may burst (haemolysis). An isotonic solution matches the cell's osmotic pressure, so there is no net water movement and the cell keeps its normal shape.
How to Study PCT 202 Effectively
- Split your revision into a theory stream (solubility, partition, phase rule, dosage forms) and a calculations stream (dilutions, alligation, ratio strength, tonicity), and give the calculations daily reps since they carry the most recoverable marks.
- Build one reference sheet of solvent facts: what mixes with what, which solvents are safe internally, and which co-solvents raise solubility, so the true/false questions become free points.
- Memorise the phase rule F = C − P + 2 and practise applying it to one- and two-component systems until the triple point and eutectic ideas feel obvious.
- For every calculation, write the formula, attach units to each number, and check the units cancel before you trust the answer. That single habit stops most careless errors.
- Drill percentage strength ↔ "1 in X" conversions both directions, and work vapour-pressure and colligative sums in moles, not grams.
- Use this guide to understand each concept first, then use the workbook below to test recall under timed conditions.
Download the Full PCT 202 Practice Workbook
When you are ready to test yourself, open the interactive reader below and work through the complete set of practice questions with the full worked answer key. Read it straight on the page or download it as a free bonus for offline revision in the run-up to your exam.
Frequently Asked Questions
Is this PCT 202 material free?
Completely free. Every study guide and workbook on EverythingABUAD is open to ABUAD students at no cost, online or as a download.
Will these exact questions appear in my exam?
No. This is an original revision set written from scratch by our student team and worded in our own way. It is not a past paper and not a prediction of any test. Treat it as practice that sharpens the concepts, and always follow your lecturer's current course outline.
Do I need to be strong at maths to pass the calculations section?
You need to be careful more than clever. Most PCT 202 calculations rely on a handful of tools, mainly C₁V₁ = C₂V₂, ratio strength, alligation and mole fractions. If you drill those with units written out every time, the arithmetic stays simple and the marks become dependable.
About this resource: All summaries, explanations, study tips, and practice questions on this page were written, paraphrased, and adapted by the EverythingABUAD student team to support exam revision. This is an original study aid, not an official ABUAD document, and it is not a prediction of any future exam. Always cross-check quantities, doses and definitions against your lecturer's current course outline and the current pharmacopoeia.
