These free B.Pharm notes on acid-base chemistry and buffers cover chapter 7 of Pharmaceutical Inorganic and Analytical Chemistry (BP106T), a first-semester subject. Read the key points below, then study the complete chapter PDF. You can browse every chapter in the Pharmaceutical Inorganic and Analytical Chemistry category.
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Overview of acid-base chemistry and buffers
These notes begin with weakly acidic and basic drugs and the Arrhenius, Bronsted-Lowry and Lewis theories. They then cover buffers, the mechanism of buffer action, buffer capacity and the physiological buffer systems of the body. Later sections deal with the preparation, criteria and stability of buffers, the pH scale and its significance, the buffer equation, and isotonicity in I.V. and ophthalmic solutions.
Key points on acid-base chemistry and buffers
- In the Bronsted-Lowry theory an acid is a proton donor and a base is a proton acceptor, while Lewis acids accept an electron pair.
- A buffer is a mixture of a weak acid with its salt of a strong base, or a weak base with its salt of a strong acid.
- Buffer capacity is the power of a buffer to resist pH change, and it is highest when the pH is equal to the pKa.
- At pH 7.4, plasma holds about 24 mEq/litre bicarbonate and 1.2 mEq/litre carbonic acid, a ratio of 20 : 1.
- A solution isotonic with blood has a freezing-point lowering of 0.52 degrees C, the same osmotic pressure as 0.9% NaCl.
Relevance to pharmacy practice
Most drugs are weak acids or weak bases, so pH and buffers decide their stability, solubility and analysis, and blood pH must stay near 7.4 for life. Making I.V. fluids and eye drops buffered and isotonic prevents discomfort, swelling and cell damage in patients.
Every chapter in this subject builds on the one before it, so do not skip topics that look simple. Definitions, principles, procedures and examples are the parts that examiners return to most often, and a clear understanding here will also make later subjects easier to follow in the coming semesters.
Frequently asked questions on acid-base chemistry and buffers
What is a buffer solution?
A buffer is a substance that resists a change in the pH of an aqueous system, usually a weak acid with its salt of a strong base, such as acetic acid and sodium acetate.
What are the main physiological buffer systems?
The main systems are the carbonic acid-bicarbonate buffer in plasma and kidneys, the phosphate buffer in cells and kidneys, and the protein or haemoglobin buffer in cells and plasma.
What are the methods of adjusting isotonicity?
Two methods are used: the cryoscopic method, which adjusts the freezing-point lowering to 0.52 degrees C, and the sodium chloride equivalent method using PSA = 0.9 – (PSM x E).
Quick revision checklist
Use this self-test after reading the chapter on acid-base chemistry and buffers. If you can do all of the following without looking at your notes, you are ready for the exam.
- I can explain: the Arrhenius, Bronsted-Lowry and Lewis theories
- I can explain: the mechanism of buffer action
- I can explain: buffer capacity and its formula
- I can explain: the three physiological buffer systems
- I can explain: isotonicity in I.V. and eye solutions
Study and exam tips
Start by reading the chapter once for the overall idea, then revise acid-base chemistry and buffers using headings, definitions, principles, reactions and examples. Short-answer questions in the university exam usually ask for definitions, principles, procedures, reactions and uses, so write these in your own words and practise the equations, tables and flow charts that the chapter has.
For wider reading, standard books and open resources such as the NCBI Bookshelf help you confirm terms and see more examples. Revise acid-base chemistry and buffers again a day later and again a week later, because spaced revision improves long-term memory.
This page is part of the Pharmaceutical Inorganic and Analytical Chemistry series for first-semester B.Pharm students on B.Pharm Guru, where every chapter has a short summary and a full PDF. Bookmark this page and share it with classmates who are preparing for the same exam.
Related notes: 9. ACID-BASE TITRATIONS, 10. NON-AQUEOUS TITRATIONS.
Next: 8. MAJOR EXTRA AND INTRACELLULAR ELECTROLYTES. Back to the Pharmaceutical Inorganic and Analytical Chemistry category.
