IMO Practice Test — Chemistry in Everyday Life
14 Questions • 15 min • Olympiad level
15:00
Question 1 of 14
A drug binds an enzyme at a site other than the active site, changing the active site's shape so the substrate cannot fit. This is best described as:
competitive inhibition
non-competitive (allosteric) inhibition
agonism
saponification
Explanation: Binding at an allosteric site that alters the active site is non-competitive (allosteric) inhibition; competitive inhibition occurs at the active site itself.
Question 2 of 14
Why was the development of H2-receptor antagonists (cimetidine, ranitidine) a major advance over antacids such as NaHCO3?
they taste better
they neutralise more acid
they prevent acid formation at its source rather than just neutralising acid present
they are cheaper
Explanation: Antacids only neutralise acid already secreted; H2 blockers stop histamine triggering secretion, treating the cause.
Question 3 of 14
Aspirin is unique among common analgesics because, in addition to relieving pain and fever, it:
is a narcotic
prevents platelet aggregation (blood clotting)
is an antibiotic
is a tranquilizer
Explanation: Aspirin's anti-platelet action makes a small daily dose useful for preventing heart attacks.
Question 4 of 14
Which combination correctly describes penicillin G?
broad-spectrum, bacteriostatic
narrow-spectrum, bactericidal
broad-spectrum, bactericidal
narrow-spectrum, bacteriostatic
Explanation: Penicillin G acts on only a few bacteria (narrow-spectrum) and kills them (bactericidal).
Question 5 of 14
Match the antiseptic-disinfectant idea: which statement is TRUE?
disinfectants are safe on open wounds
the same phenol solution is an antiseptic at 0.2% and a disinfectant at 1%
tincture of iodine is a disinfectant only
all antiseptics can be safely swallowed
Explanation: Strength decides the role: 0.2% phenol (antiseptic) versus 1% phenol (disinfectant); disinfectants are too harsh for living tissue.
Question 6 of 14
An antioxidant protects a fatty food from rancidity because it is:
more easily oxidised than the food, so it is consumed first
a strong oxidising agent itself
a preservative that kills bacteria
a sweetener
Explanation: Being more readily oxidised, the antioxidant (e.g. BHA, BHT) reacts with oxygen in preference to the food.
Question 7 of 14
Order these sweeteners by increasing sweetness relative to sucrose: aspartame, saccharin, alitame.
alitame < saccharin < aspartame
aspartame < saccharin < alitame
saccharin < aspartame < alitame
aspartame < alitame < saccharin
Explanation: Aspartame is about 100x, saccharin about 550x and alitame about 2000x sweeter than sucrose.
Question 8 of 14
Why does sucralose succeed where aspartame fails in baked products?
sucralose is sweeter
sucralose is stable to heat while aspartame decomposes on heating
aspartame is toxic
sucralose adds more calories
Explanation: Sucralose is heat-stable; aspartame breaks down on heating, so only sucralose suits cooking and baking.
Question 9 of 14
Which type of detergent is best matched with its typical application?
cationic — liquid dishwashing
non-ionic — hair conditioner
anionic — household washing and toothpaste
anionic — germicide in hospitals
Explanation: Anionic detergents are used in washing and toothpastes; cationic ones (germicidal) in conditioners; non-ionic in liquid dishwashing.
Question 10 of 14
A washing detergent that causes persistent foaming in rivers most likely has:
a straight hydrocarbon chain (biodegradable)
a highly branched chain (non-biodegradable)
no hydrocarbon tail
an ionic head only
Explanation: Branched-chain detergents resist bacterial breakdown, so they persist and foam in water bodies.
Question 11 of 14
In the cleansing action of soap, grease is removed because it is:
dissolved by the hydrophilic heads
trapped inside a micelle with tails embedded in the grease and heads in water, then emulsified away
neutralised by alkali
oxidised by the soap
Explanation: The hydrophobic tails bury in the grease and the hydrophilic heads face water, forming a micelle that lifts and suspends the dirt.
Question 12 of 14
Sodium stearate, C17H35COONa, is best classified as:
a synthetic anionic detergent
a soap (sodium salt of a long-chain fatty acid)
a cationic detergent
a preservative
Explanation: Soaps are the sodium or potassium salts of long-chain fatty acids; sodium stearate is a typical soap, not a synthetic detergent.
Question 13 of 14
A drug used when a natural chemical messenger must be blocked rather than supplied would be a/an:
agonist
antagonist
preservative
antioxidant
Explanation: Antagonists occupy the receptor without activating it, blocking the natural message; agonists supply/mimic it.
Question 14 of 14
Which statement about saponification is correct?
it is acid hydrolysis of an ester giving a detergent
it is alkaline hydrolysis of fat/oil giving soap and glycerol
it produces only glycerol
it requires Ca2+ ions
Explanation: Saponification boils a fat/oil with NaOH to give soap plus glycerol: fat + 3NaOH → soap + glycerol.