Acetylsalicylic Acid (Aspirin) Identification: Key Facts at a Glance
- Physical Properties: Physical Appearance · Solubility · Flame Test · Melting Point (135–136 °C) · Molecular Formula (C₉H₈O₄) · MW (180.16 g/mol) · pKa –COOH (3.50) · CAS No. (50-78-2) · IUPAC Name (2-(Acetyloxy)benzoic acid) · Brand Name (Aspirin)
- Chemical Tests & Coverage: Litmus · NaHCO₃ Test · Ester Test · FeCl₃ Test (no violet — intact ester) · Hydrolysis + FeCl₃ (violet — confirms ester group) · Bromine Water · Hydroxamic Acid Test · Mixed Melting Point · Chemical Structure · Functional Groups · Hydrolysis · Applications · Safety · FAQs · MCQs · Viva Questions
What Is Acetylsalicylic Acid? — Introduction and Background
Acetylsalicylic acid is an acetyl ester derivative of salicylic acid, universally known by its brand name aspirin. Its molecular formula is C₉H₈O₄ (also written as CH₃COOC₆H₄COOH), with a molar mass of 180.16 g/mol. The IUPAC name of acetylsalicylic acid is 2-(acetyloxy)benzoic acid; it is also systematically named 2-acetoxybenzoic acid. The generic name is acetylsalicylic acid, while its most recognisable brand name worldwide is Aspirin (originally trademarked by Bayer AG in 1899).
Acetylsalicylic acid presents as a white, odourless crystalline powder or needle-like crystals. It has a slightly bitter taste and is stable under normal conditions but hydrolyses in the presence of moisture to produce salicylic acid and acetic acid — the latter giving a characteristic vinegar-like odour, which serves as a useful preliminary identification clue. The classification of acetylsalicylic acid places it in the non-steroidal anti-inflammatory drug (NSAID) category and, more broadly, within the salicylate group of drugs.
|
Property |
Value |
Significance for Identification or Context |
|
Molecular formula |
C₉H₈O₄ (CH₃COOC₆H₄COOH) |
Three functional regions: benzene ring, ester (–OCOCH₃), and carboxylic acid (–COOH). Four oxygen atoms distinguish it from benzoic acid (two oxygens) and salicylic acid (three oxygens). |
|
Molar mass |
180.16 g/mol |
Calculated as : 9×C (108.09) + 8×H (8.06) + 4×O (64.00) = 180.16 g/mol. Used in dose calculations and synthesis yield determination. |
|
IUPAC name |
2-(Acetyloxy)benzoic acid |
Also accepted: 2-acetoxybenzoic acid. Common name: acetylsalicylic acid. Brand name: Aspirin. Generic name: acetylsalicylic acid. |
|
CAS Number |
50-78-2 |
The acetylsalicylic acid CAS no. 50-78-2 is the globally recognised chemical identifier for aspirin used in databases and safety data sheets (SDS). |
|
Colour & appearance |
White crystalline powder or needles; odourless when pure |
On hydrolysis or ageing, a vinegar-like (acetic acid) odour develops — an important qualitative clue to the presence of the ester group. |
|
Melting point |
135–136°C |
Sharp m.p. is a purity indicator. Depression of m.p. indicates hydrolysis to salicylic acid (m.p. 159°C) or other impurities. |
|
Boiling point |
No true boiling point. |
Acetylsalicylic acid does not have a true boiling point — it decomposes before boiling. This decomposition produces salicylic acid and acetic acid. This is a distinguishing feature from stable aromatic acids like benzoic acid (b.p. 249°C). |
|
Density |
1.40 g/cm³ (20°C) |
Denser than water. The acetylsalicylic acid density is higher than benzoic acid (1.266 g/cm³) due to its more complex molecular architecture and the additional oxygen atoms. |
|
Solubility in water |
Approximately 3–3.3 g/L at room temperature. |
Solubility increases at elevated pH (ionises in NaHCO₃ and NaOH). Freely soluble in ethanol, acetone, chloroform. |
|
pKa |
3.50 (–COOH) |
More acidic than benzoic acid (pKa 4.20) due to the electron-withdrawing ester group at the ortho position. Reacts readily with NaHCO₃ to evolve CO₂. |
|
Half-life |
∼15–20 minutes (in vivo) |
Acetylsalicylic acid half life in the bloodstream is very short — it is rapidly hydrolysed by plasma and liver esterases to salicylic acid (the active metabolite for many effects). The salicylic acid half-life is 2–3 hours (analgesic dose) to 15–30 hours (anti-inflammatory dose). |
|
Functional groups |
Benzene ring + –COOH + –OCOCH₃ (ester) |
Acetylsalicylic acid functional groups: (1) benzene ring — aromatic, sooty flame; (2) carboxylic acid –COOH — reacts with NaHCO₃, esterification; (3) ester –OCOCH₃ — hydrolysis to salicylic acid + acetic acid (vinegar odour). |
|
Hydrolysis |
C₉H₈O₄ + H₂O → C₇H₆O₃ + CH₃COOH |
Acetylsalicylic acid hydrolysis produces salicylic acid and acetic acid. In alkaline solution (NaOH), hydrolysis is rapid and complete. Salicylic acid formed gives a violet/purple colour with FeCl₃ (phenolic –OH is now free), a key diagnostic distinction from intact aspirin. |
How Do You Identify Acetylsalicylic Acid from Its Structure?🔍
Every competent qualitative analysis begins not at the bench, but on paper. Before a single reagent is added, the structural formula of acetylsalicylic acid must be examined carefully. The formula C₉H₈O₄ contains three distinct functional regions — each one a direct instruction for a specific test.
Look at the structure of acetylsalicylic acid in Figure 1. You can spot three main parts. The most important question when testing this compound is: “Is the ester group still intact, or has it broken down into salicylic acid?”
This matter is decided by the FeCl₃ test. If the ester(acetylsalicylic) is present, the FeCl₃ test shows no colour change. If it has broken down (salicylic acid is formed ), it gives intense the violet color — because free salicylic acid (a phenol) is now present.
Step 1: Identify the Functional Groups in Acetylsalicylic Acid
- 🔵 Benzene ring — aromatic character; high C:H ratio
- 🟣 –COOH group — carboxylic acid; primary acidic centre
- 🟡 –OCOCH₃ group — ester; hydrolysable; gives acetic acid (vinegar odour) on hydrolysis
Difference between Acetylsalicylic acid and Salicylic acid
Acetylsalicylic acid also has 3 functional groups:
- Benzene ring
- Carboxyl group (–COOH)
- Ester group (–OCOCH₃)
Salicylic acid has 3 functional groups:
- Benzene ring
- Carboxyl group (–COOH)
- Phenol group (–OH on benzene)
When acetylsalicylic acid hydrolyses, the ester breaks down and a free phenol (–OH) is produced — converting it back to salicylic acid.
FeCl₃ test distinguishes the between Acetylsalicylic acid and Salicylic acid:
|
Compound |
FeCl₃ Result |
|
Acetylsalicylic acid |
No colour (ester intact, no free phenol) |
|
Salicylic acid |
Violet colour (free phenol present) |
Step 2: Match Each Structural Clue to Its Confirmatory Test
|
Structural Clue |
Tests to Confirm It |
|
🔵 Benzene ring (aromatic) |
Flame Test — sooty, smoky luminous yellow flame |
|
🟣 –COOH (carboxylic acid group) |
Litmus Paper Test • NaHCO₃ Test (CO₂ evolution) • Ester Test (acid-catalysed esterification with ethanol) |
|
🟡 –OCOCH₃ (ester group) |
Hydrolysis Test — acetic acid (vinegar) odour on warming with NaOH or water; FeCl₃ test on hydrolysed product → violet (salicylic acid formed) |
|
⚪ Whole compound (intact) |
FeCl₃ Test (no violet/buff only — intact ester; violet = hydrolysis has occurred) • Melting point 135–136°C • Odour check (no vinegar = pure; vinegar = hydrolysed) |
Step 3: Always Begin with Preliminary Observations
Three preliminary observations immediately narrow the field: the physical appearance (white, odourless or faint vinegar-odoured crystalline solid), the solubility behaviour in water (slightly soluble in cold water, freely soluble in NaOH or NaHCO₃ solution), and the melting point (135–136°C, sharp for pure sample). A compound matching all three already points strongly toward acetylsalicylic acid. Chemical tests then confirm the functional groups.
The Testing Sequence: Step-by-Step Flow
Note: The table summarises only what each test establishes and why it matters for the identification of cinnamic acid. Full procedural details — quantities, conditions, safety notes, and interpretation of borderline results — are provided on the page dedicated to each test. Readers are strongly encouraged to study the relevant page before attempting any procedure in the laboratory.
|
# |
Test |
What It Establishes |
|
1 |
Physical Appearance |
White crystalline solid; faint or no odour (vinegar smell = hydrolysis has occurred) |
|
2 |
Solubility |
Slightly soluble in cold water; freely soluble in NaOH (forms sodium acetylsalicylate) |
|
3 |
Odour/Hydrolysis Preliminary |
Warm with water: acetic acid (vinegar) odour confirms ester group |
|
4 |
Flame Test |
Benzene ring present (sooty yellow flame) |
|
5 |
Litmus Test |
Compound is acidic |
|
6 |
NaHCO₃ Test |
Carboxylic acid confirmed; CO₂ evolved (phenols excluded by pKa) |
|
7 |
Ester Test (Esterification) |
Free –COOH confirmed by Fischer esterification with ethanol |
|
8 |
FeCl₃ Test (intact sample) |
No violet with intact aspirin (ester present, no free –OH); |
|
9 |
Hydrolysis + FeCl₃ Test |
Ester group confirmed: hydrolysis releases salicylic acid → violet FeCl₃ colour |
|
10 |
Melting Point |
Purity check; identity against literature (135–136°C) |
|
11 |
Mixed Melting Point |
Gold-standard definitive proof of identity |
The analytical power of acetylsalicylic acid qualitative analysis lies in the contrast between its FeCl₃ response before and after hydrolysis. Intact aspirin gives no violet; hydrolysed aspirin gives an intense violet. This single observation identifies the ester functional group as definitively as any other chemical test.
Materials and Reagents Required for Acetylsalicylic Acid Identification
- Acetylsalicylic acid sample (unknown)
- Distilled water
- NaHCO₃ solution (aqueous, ∼5%) — for carboxylic acid confirmation
- Freshly prepared lime water (Ca(OH)₂) — for CO₂ confirmation
- Blue and red litmus paper
- Absolute ethanol — for ester test
- Concentrated H₂SO₄ — for ester test
- Neutral FeCl₃ solution (∼1% aqueous) — for FeCl₃ test (intact and hydrolysed)
- Dilute NaOH solution (2 mol L⁻¹) — for alkaline hydrolysis
- Melting point apparatus with sealed capillary tubes
- Authentic (known) acetylsalicylic acid sample — for control test and mixed melting point
- Authentic salicylic acid sample — for comparison in FeCl₃ test
Qualitative Analysis of Acetylsalicylic Acid — Procedure & Observations
|
Test |
Procedure |
Observation |
Inference |
|
Physical Appearance |
Examine a small sample on a white tile. Observe colour, crystal form, and odour. |
White crystalline powder or needle-like solid. Pure sample is odourless or very faintly vinegary. Bitter taste (do not test). |
White, odourless acetylsalicylic acid appearance is consistent with a pure aromatic ester-acid compound. A vinegar odour immediately signals partial hydrolysis — acetic acid is being released from the ester group. |
|
Solubility |
Add to (A) cold water, (B) hot water, (C) NaOH solution. Observe each. |
Slightly soluble in cold water; more soluble on warming. Dissolves readily in NaOH. |
Slight water solubility reflects both the hydrophobic ring and the ester group. Free dissolution in NaOH confirms the ionisable –COOH group: C₉H₈O₄ + NaOH → sodium acetylsalicylate + H₂O. |
|
Odour / Hydrolysis (Preliminary) |
Place a small quantity in a test tube with 3 mL dilute NaOH (2 mol L⁻¹). Warm gently at 50–60 °C for 2–3 min. Cool, then acidify with dilute H₂SO₄ until effervescence ceases. Waft and detect odour. |
N: No Prussian blue color formed. A pure, dry sample gives little or no odour in cold water. A strong vinegar odour develops on acidification after alkaline hydrolysis, and also with —aged
|
Confirms hydrolysis of the ester group: acetylsalicylic acid + H₂O → salicylic acid + CH₃COOH (acetic acid). The vinegar odour is the acetyl group being cleaved. Alkaline conditions convert the acetic acid to non-volatile sodium acetate, so the solution must be acidified before the odour can be detected. This is unique to ester-containing compounds. |
|
Flame Test |
Introduce a tiny quantity into the outer edge of a Bunsen flame on a spatula. |
Burns with a bright, sooty yellow flame. Black carbonaceous soot visible. |
Sooty flame confirms the high C:H ratio of an aromatic compound. The benzene ring’s incomplete combustion produces soot. Indicates aromatic character of given organic compound. |
|
Litmus Test |
Dissolve in warm water. Dip blue and red litmus strips. |
Blue litmus turns red. Red litmus unchanged. |
Confirms acidic compound. Insufficient alone to distinguish –COOH from phenol or ester — proceed to NaHCO₃ test. |
|
NaHCO₃ Test |
Add a pinch of cinnamic acid to NaHCO₃ solution. Pass evolved gas through freshly prepared lime water using a delivery tube. |
Brisk effervescence; gas evolved turns lime water milky. |
Gas confirmed as CO₂ (Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O). Specific to carboxylic acids (pKa ≈ 4–5), since phenols (pKa ≈ 10) are too weakly acidic to react with NaHCO₃. |
|
Ester Test |
Mix with absolute ethanol + conc. H₂SO₄. Warm at 60–70°C for 3–4 min. Pour into cold water. Waft. |
A sweet, fruity odour develops on pouring into cold water. |
Esterification occurs, but this is not conclusive for –COOH. Under these conditions the –OCOCH₃ group is partly cleaved, so the odour observed is largely ethyl acetate; the NaHCO₃/CO₂ test remains the definitive proof of the free carboxylic acid. |
|
FeCl₃ Test (Intact Sample) |
Dissolve intact sample in water or dilute ethanol. Add 3–4 drops neutral FeCl₃. Compare with salicylic acid control. |
Intact acetylsalicylic acid: no violet/purple. Pale yellow or no colour change only. Salicylic acid control: intense violet/purple. |
Absence of violet confirms the ester group (–OCOCH₃) is intact and the phenolic –OH is blocked. Salicylic acid (with free phenolic –OH) gives intense violet: C₆H₄(OH)(COOH) + FeCl₃ → [Fe{C₆H₄(O)COO}]Cl + 2 HCl (violet ferric salicylate chelate). Aspirin cannot form this complex — the –OH is acetylated. |
|
Hydrolysis + FeCl₃ Test |
Boil a portion with 2 mL dilute NaOH (2 mol L⁻¹) for 2–3 min. Acidify with HCl. Add FeCl₃ drops. |
After alkaline hydrolysis, intense violet/purple colour develops with FeCl₃ |
Alkaline hydrolysis cleaves the ester: C₉H₈O₄ + 2NaOH → C₆H₄(OH)(COONa) + CH₃COONa + H₂O. Acidification liberates salicylic acid → its free phenolic –OH now reacts with FeCl₃ to give violet. This two-stage test definitively confirms the acetylsalicylic acid. |
|
Melting Point |
Pack dry powdered sample in sealed capillary. Heat at 1–2°C/min from ∼125°C. |
Sharp melting point at 135–136°C over a range of less than 1°C. |
Matches literature m.p. of acetylsalicylic acid (135–136°C). A depressed or broadened m.p. (e.g. 120–130°C) indicates hydrolysis impurity (salicylic acid, m.p. 159°C, forms a eutectic with aspirin). |
|
Mixed Melting Point |
Mix equal masses of unknown and certified authentic acetylsalicylic acid. Determine m.p. |
Mixture melts sharply at 135–136°C. No depression. |
No m.p. depression confirms both samples are the same compound. Strong evidence of identity and purity. |
Quick-Reference: What Are the Expected Results for Acetylsalicylic Acid Identification?
|
# |
Test |
Positive Result (Acetylsalicylic Acid) |
What It Confirms |
|
1 |
Physical Appearance |
White crystalline solid; no colour; faint or no odour |
Purity; no chromophore; ester intact if odourless |
|
2 |
Solubility |
Slightly soluble in cold water; freely soluble in NaOH |
Acidic –COOH + aromatic ring |
|
3 |
Odour Test |
Vinegar odour on warming with water |
Ester group (–OCOCH₃) present; hydrolysis to acetic acid |
|
4 |
Flame Test |
Bright, sooty yellow flame + black smoke |
Benzene ring (aromatic compound) |
|
5 |
Litmus Test |
Blue litmus → red; red litmus unchanged |
Acidic compound |
|
6 |
NaHCO₃ Test |
Brisk effervescence; lime water milky (CO₂) |
Carboxylic acid; phenols excluded |
|
7 |
Ester Test |
Sweet/fruity odour of new ester product |
Free –COOH confirmed; esterification possible |
|
8 |
FeCl₃ Test (intact) |
No violet/purple (pale yellow or none) |
Phenolic –OH absent; ester group intact |
|
9 |
Hydrolysis + FeCl₃ |
Intense violet/purple after NaOH hydrolysis |
Ester group confirmed; salicylic acid liberated |
|
10 |
Melting Point |
Sharp m.p. 135–136°C; range <1°C |
Identity + purity |
|
11 |
Mixed Melting Point |
No depression; sharp m.p. 135–136°C |
Gold-standard definitive proof of identity |
What Chemical Reactions Does Acetylsalicylic Acid Undergo?
|
Reaction |
Equation and Mechanism Notes |
|
NaHCO₃ Test |
C₉H₈O₄ + NaHCO₃ → C₉H₇O₄Na + H₂O + CO₂↑ (Acid–base: –COOH group reacts; CO₂ confirmed by lime water: CO₂ + Ca(OH)₂ → CaCO₃↓ + H₂O) |
|
NaOH Reaction (Solubility) |
C₉H₈O₄ + NaOH → C₉H₇O₄Na + H₂O (Salt formation: sodium acetylsalicylate. With excess NaOH and heating, also hydrolyses the ester: C₉H₈O₄ + 2NaOH → C₆H₄(OH)(COONa) + CH₃COONa + H₂O) |
|
Hydrolysis of Ester Group (Key Diagnostic Reaction) |
C₉H₈O₄ + H₂O → C₆H₄(OH)(COOH) + CH₃COOH (Acid-catalysed or thermal; produces salicylic acid + acetic acid. Acetic acid = vinegar odour. Alkaline hydrolysis is faster: C₉H₈O₄ + 2NaOH → sodium salicylate + sodium acetate + H₂O) |
|
FeCl₃ Test on Hydrolysed Product |
3 C₆H₄(OH)(COOH) + FeCl₃ → [Fe(C₆H₄(OH)COO)₃] + 3 HCl (violet complex) (The free phenolic –OH of salicylic acid coordinates with Fe³⁺ to form an intense violet ferric salicylate complex; in aqueous solution the actual species is a polynuclear iron(III) salicylate-hydroxo complex, and this simplified equation suffices for qualitative identification purposes. Intact acetylsalicylic acid — no free –OH — gives no violet.) |
|
Esterification (Ester Test) |
C₉H₈O₄ + C₂H₅OH ⇌ (conc. H₂SO₄, Δ) ethyl acetylsalicylate + H₂O (Fischer esterification of the –COOH group; confirms free carboxylic acid; sweet ester odour detected) |
|
Synthesis of Acetylsalicylic Acid from Salicylic Acid |
C₆H₄(OH)(COOH) + (CH₃CO)₂O → C₉H₈O₄ + CH₃COOH (Acetylation of the phenolic –OH of salicylic acid by acetic anhydride, catalysed by H₃PO₄ or H₂SO₄. The –COOH group is not acetylated under these conditions. Product is acetylsalicylic acid from salicylic acid.) |
Laboratory Note: Use a freshly prepared, approximately neutral ferric chloride solution. Acidic reagent suppresses phenolate formation, whereas alkaline solutions may produce Fe(OH)₃ precipitates and reduce test sensitivity.
How Is Acetylsalicylic Acid Confirmed Experimentally?
All observations are consistent with the identity of the compound as acetylsalicylic acid (C₉H₈O₄), commonly known as aspirin.
The sample was a white crystalline solid, slightly soluble in cold water but freely soluble in NaOH, confirming the presence of an ionisable –COOH group (forming sodium acetylsalicylate).
The flame test produced a sooty yellow flame, confirming the aromatic benzene ring. The litmus and NaHCO₃ tests confirmed acidity; CO₂ gas (turning lime water milky) was produced, confirming –COOH and excluding phenols. Esterification with ethanol produced a sweet smell, excluding sulfonic acids. The vinegar smell on warming confirmed the presence of a hydrolysable ester group (–OCOCH₃).
Salicylic acid contains a free phenolic –OH group, which gives violet colour with FeCl₃. Acetylsalicylic acid has no free phenolic –OH (it is protected as an ester), so FeCl₃ gives no colour. When the original sample was treated with FeCl₃, no colour change occurred — confirming the ester was intact. After alkaline hydrolysis, FeCl₃ gave an intense violet colour — confirming that the ester was cleaved and free salicylic acid (with a free phenolic –OH) was produced.
The melting point was sharp at 135–136°C, matching the literature value, and the mixed melting point showed no depression.
Thus, all tests logically and conclusively prove that the given sample is acetylsalicylic acid (C₉H₈O₄).
Conclusion
Acetylsalicylic Acid (C₉H₈O₄) — Aspirin
IUPAC name: 2-(acetyloxy)benzoic acid | Molar mass: 180.16 g/mol | M.p. 135–136°C | CAS: 50-78-2
Uses and Applications of Acetylsalicylic Acid
|
Field / Application |
Use |
Details |
|
Pain & Fever |
Analgesic and antipyretic |
Acetylsalicylic acid 325–650 mg (standard tablet) provides analgesia for headache, dental pain, and musculoskeletal pain, and reduces fever by inhibiting prostaglandin synthesis in the hypothalamus. Acetylsalicylic acid effervescent tablets 325 mg offer rapid dissolution and onset. |
|
Anti-inflammatory |
NSAID at higher doses |
At doses of 4–6 g/day in divided doses, acetylsalicylic acid provides significant anti-inflammatory effects used historically in rheumatic fever and arthritis. Classified as an NSAID (non-steroidal anti-inflammatory drug) and salicylate. |
|
Pregnancy |
Low-dose use in high-risk pregnancies |
Acetylsalicylic acid in pregnancy at low dose (75–81 mg) is prescribed by obstetricians for women at high risk of pre-eclampsia and intrauterine growth restriction. Use during pregnancy is otherwise generally contraindicated, especially in the third trimester (risk of premature closure of ductus arteriosus and neonatal bleeding). |
|
Organic Synthesis |
Preparation of aspirin (teaching synthesis) |
The synthesis of acetylsalicylic acid from salicylic acid and acetic anhydride is one of the most common undergraduate chemistry laboratory preparations, illustrating Fischer esterification-type acetylation chemistry and product recrystallisation. |
Reagent Hazard Summary
|
Reagent |
Hazard |
Key Precaution |
|
Acetylsalicylic acid |
Mild irritant • Avoid ingestion |
Avoid inhalation of dust. Normal bench handling with gloves. Do not taste. |
|
Conc. H₂SO₄ |
CORROSIVE • OXIDISING |
Add to mixture slowly. Goggles + acid-resistant gloves. Fume cupboard. |
|
NaOH solution |
CORROSIVE |
Gloves and goggles. Concentrated NaOH causes chemical burns. |
|
FeCl₃ solution |
IRRITANT |
Gloves and goggles. Dispose in heavy-metal waste container. |
|
Ethanol (absolute) |
FLAMMABLE |
Keep away from flames. No smoking in laboratory. |
FAQ’s
Multiple Choice Questions
MCQ 1
1. The correct molecular formula of acetylsalicylic acid is:
A. C₇H6O₃ (salicylic acid)
B. C₆H₅COOH (benzoic acid)
C. C₉H₈O₄ (acetylsalicylic acid)
D. C₈H₈O₃ (methyl salicylate)
MCQ 2
2. Which of the following is the generic (INN) name for aspirin?
A. Salicylic acid
B. Acetylsalicylic acid
C. Acetoxybenzoic acid only
D. Sodium salicylate
MCQ 3
3. How many distinct functional groups does acetylsalicylic acid (C₉H₈O₄) contain?
A. One (–COOH only)
B. Two (benzene ring and –COOH)
C. Three (benzene ring, –COOH, and ester –OCOCH₃)
D. Four (benzene ring, –COOH, ester, and phenolic –OH)
MCQ 4
4. Acetylsalicylic acid is generally safe at low dose (75–81 mg/day) in pregnancy for:
A. All three trimesters without restriction
B. First-trimester fever only
C. Prevention of pre-eclampsia in high-risk pregnancies (started at 12–16 weeks, continued under medical supervision)
D. Post-term labour induction
MCQ 5
5. Which of the following is a contraindication to acetylsalicylic acid use?
A. Hypertension (unless antiplatelet therapy indicated)
B. Viral infections in children under 16 (risk of Reye’s syndrome)
C. Mild anaemia
D. Type 2 diabetes mellitus
MCQ 6
6. The antiplatelet dose of acetylsalicylic acid for cardiovascular prevention is:
A. 325–650 mg four times daily
B. 2–4 g/day in divided doses
C. 75–81 mg once daily
D. 500 mg every 6 hours
MCQ 7
7. The products of complete alkaline hydrolysis of acetylsalicylic acid with 2 equivalents of NaOH are:
A. Salicylic acid + acetic acid
B. Sodium salicylate + sodium acetate + water
C. Benzoic acid + acetic acid
D. Sodium benzoate + acetic anhydride
MCQ 8
8. Which functional group in acetylsalicylic acid is confirmed by the vinegar odour test?
A. Carboxylic acid (–COOH)
B. Benzene ring
C. Ester group (–OCOCH₃) – hydrolysis releases acetic acid
D. Phenolic –OH
MCQ 9
9. The FeCl₃ test on intact (unhydrolysed) acetylsalicylic acid gives:
A. The FeCl₃ test on intact (unhydrolysed) acetylsalicylic acid gives:
B. Buff/salmon precipitate
C. No violet; pale yellow or no colour change
D. Deep red coloration
