Free practice paper · 2027 format
The whole written test in LF1's format: 25 Chemistry, 25 Biology and 25 General Science questions, four options and one best answer each, with the answer and a full explanation for every one. LF1's own mock gives only a key; this paper explains why each answer is right. Written by IvyTest; it is not an official Charles University paper.
Before you start
| Section | Questions | Time | Marks (Medicine and Dentistry Entrance Examination) |
|---|---|---|---|
| Chemistry | 25 | – | +1 correct, 0 wrong, 0 blank |
| Biology | 25 | – | +1 correct, 0 wrong, 0 blank |
| General Science | 25 | – | +1 correct, 0 wrong, 0 blank |
Give yourself 90 minutes for all 75 questions, about 72 seconds each, and answer on paper before opening any explanation. A wrong answer costs nothing, so answer every question. LF1 converts each part's score to a percentage and decides who goes on to the MMI on the sum of the three, so the tally at the end of the page scores each part on its own. The MMI, which alone decides admission, is not on paper.
Section 1 of 3
25 questions
Chlorine has atomic number 17. How many neutrons and how many electrons does the ion ³⁷Cl⁻ contain?
Answer: B
The number of neutrons is the mass number minus the atomic number, 37 − 17 = 20, and the negative charge means one electron has been gained, giving 17 + 1 = 18 electrons. Sixteen electrons would be the count for a positive ion, Cl⁺; a negative charge always means more electrons than protons.
How many unpaired electrons does a phosphorus atom (atomic number 15) have in its ground state?
Answer: D
The configuration is 1s² 2s² 2p⁶ 3s² 3p³, and by Hund's rule the three 3p electrons occupy the three 3p orbitals singly with parallel spins, so three are unpaired. Five is the number of valence electrons, but the two 3s electrons are paired in the same orbital.
First ionisation energy generally increases across period 3 from sodium to argon. Which of the following elements has a LOWER first ionisation energy than the element immediately before it in the period?
Answer: A
Aluminium (3s² 3p¹) loses an electron from a 3p orbital, which is higher in energy than magnesium's filled 3s and partly shielded by it, so it is easier to remove. Phosphorus is the tempting choice, but it is higher than silicon; the second dip in the period comes one place later, at sulfur, where the first electron pairs up in a 3p orbital and is repelled by its partner.
What is the formula of calcium phosphate, the main mineral of bone, formed from Ca²⁺ ions and phosphate ions PO₄³⁻?
Answer: C
The charges must cancel: three Ca²⁺ give +6 and two PO₄³⁻ give −6, so the formula is Ca₃(PO₄)₂. CaPO₄ would carry an overall charge of −1, and Ca₃PO₄ (three calcium ions with one phosphate) would be +3, so neither is neutral.
In which of the following species is there a co-ordinate (dative) covalent bond?
Answer: A
The ammonium ion forms when the lone pair on the nitrogen of NH₃ is donated to an H⁺ ion, which brings no electron of its own: both electrons of that bond come from one atom. Water has two lone pairs but uses neither of them to bond; its two O–H bonds are ordinary covalent bonds, each atom supplying one electron, and NaCl is ionic.
What is the systematic name of Fe₂(SO₄)₃?
Answer: D
Three sulfate ions carry a total charge of −6, shared between two iron ions, so each iron is +3 and the name is iron(III) sulfate. Iron(II) sulfate is FeSO₄; sulfite is SO₃²⁻, not SO₄²⁻; and a sulfide contains S²⁻ with no oxygen at all.
How many water molecules are there in 9.0 g of water? (Relative atomic masses: H = 1, O = 16; Avogadro's number = 6.0 × 10²³ mol⁻¹)
Answer: B
The molar mass of water is 2 × 1 + 16 = 18 g/mol, so 9.0 g is 0.50 mol, which contains 0.50 × 6.0 × 10²³ = 3.0 × 10²³ molecules. The figure 5.4 × 10²⁴ comes from multiplying the mass in grams by Avogadro's number without first converting it to moles.
A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass, and its relative molecular mass is 60. What is its molecular formula? (Relative atomic masses: H = 1, C = 12, O = 16)
Answer: C
In 100 g there are 40.0/12 = 3.33 mol C, 6.7/1 = 6.7 mol H and 53.3/16 = 3.33 mol O, a ratio of 1 : 2 : 1, so the empirical formula is CH₂O (mass 30). The molecular mass 60 is twice that, giving C₂H₄O₂. C₃H₈O also has a relative molecular mass of 60, but its percentages (60% C) do not fit the analysis.
Ammonia is made by the reaction N₂ + 3H₂ → 2NH₃. A mixture of 28 g of nitrogen and 9.0 g of hydrogen reacts, and 25.5 g of ammonia is obtained. What is the percentage yield? (Relative atomic masses: H = 1, N = 14)
Answer: A
There is 28/28 = 1.0 mol N₂ and 9.0/2 = 4.5 mol H₂; 1.0 mol N₂ needs only 3.0 mol H₂, so nitrogen is the limiting reagent and the theoretical yield is 2.0 mol NH₃ = 34 g. The yield is 25.5/34 = 75%. Basing the calculation on hydrogen instead gives 3.0 mol (51 g) of ammonia and a yield of 50%, but there is not enough nitrogen to use all the hydrogen.
5.85 g of sodium chloride is dissolved in water and the solution is made up to 250 cm³. What is the molar concentration of the solution? (Relative atomic masses: Na = 23, Cl = 35.5)
Answer: D
The molar mass of NaCl is 23 + 35.5 = 58.5 g/mol, so 5.85 g is 0.100 mol, and 0.100 mol in 0.250 dm³ is 0.40 mol/dm³. The answer 0.10 mol/dm³ is the amount in moles, forgetting that the volume is a quarter of a cubic decimetre, not a whole one; 23.4 is the concentration in g/dm³, not mol/dm³.
Which of the following aqueous solutions has the LOWEST freezing point? Assume every salt dissociates completely.
Answer: C
Freezing-point depression is a colligative property: it depends on the concentration of dissolved particles, not on what they are. CaCl₂ gives three ions per formula unit (0.30 mol/kg of particles), more than NaCl (0.20), urea (0.15) or glucose (0.10). Urea looks the most concentrated, but as a non-electrolyte it does not dissociate.
In the reaction HCO₃⁻ + H₂O ⇌ CO₃²⁻ + H₃O⁺, which of the following is a conjugate acid–base pair?
Answer: B
A conjugate pair differs by exactly one proton: HCO₃⁻ donates H⁺ and becomes CO₃²⁻, its conjugate base. HCO₃⁻ and H₃O⁺ are both acids in this equation, one on each side, but they are not related by the loss or gain of a single proton.
What is the pH of a 0.0050 mol/dm³ solution of sulfuric acid at 25 °C, assuming that both protons dissociate completely?
Answer: A
Each H₂SO₄ releases two H⁺ ions, so [H⁺] = 2 × 0.0050 = 0.010 mol/dm³ = 10⁻² mol/dm³ and pH = 2. Taking −log of 0.0050 directly (about 2.3) treats sulfuric acid as if it gave only one proton per molecule.
A solution of sodium hydroxide has a pH of 11 at 25 °C. It is diluted with water to 100 times its original volume. What is the pH of the diluted solution?
Answer: D
At pH 11 the pOH is 14 − 11 = 3, so [OH⁻] = 10⁻³ mol/dm³; diluting 100 times gives 10⁻⁵ mol/dm³, pOH 5 and pH 14 − 5 = 9. A base moves towards pH 7 on dilution, so an answer above 11 is impossible, and pH 10 is the result of only a tenfold dilution: each tenfold dilution of a strong base lowers the pH by one unit.
In a galvanic cell, a zinc electrode in zinc sulfate solution is connected to a copper electrode in copper(II) sulfate solution, with a salt bridge between the two solutions. Which statement about the working cell is correct?
Answer: B
Zinc is the more reactive metal, so it is oxidised (Zn → Zn²⁺ + 2e⁻); oxidation takes place at the anode, and the released electrons travel through the wire to the copper, where Cu²⁺ is reduced. The salt bridge carries ions, never electrons; and as copper is deposited, the copper electrode gains mass rather than losing it.
In acidic solution, permanganate oxidises iron(II): MnO₄⁻ is reduced to Mn²⁺ and Fe²⁺ is oxidised to Fe³⁺. How many moles of Fe²⁺ are oxidised by 0.020 mol of MnO₄⁻?
Answer: C
Manganese goes from +7 in MnO₄⁻ to +2, so each permanganate ion accepts five electrons, while each Fe²⁺ gives up only one; the balanced ratio is MnO₄⁻ : Fe²⁺ = 1 : 5, and 0.020 × 5 = 0.10 mol. A 1 : 1 ratio, the tempting shortcut, ignores the electron count that a redox equation must balance.
Which statement correctly describes how a catalyst affects a reversible reaction?
Answer: A
A catalyst lowers the activation energy of the forward and the reverse reaction equally, so both speed up and the equilibrium mixture is the same, only reached faster. Raising the kinetic energy of the particles is what heating does, not a catalyst; and the enthalpy change depends only on reactants and products, so a catalyst cannot alter it.
For the equilibrium N₂O₄(g) ⇌ 2NO₂(g), ΔH = +58 kJ/mol. Which pair of changes would BOTH increase the amount of NO₂ at equilibrium?
Answer: D
The forward reaction is endothermic, so a higher temperature favours it, and it turns one mole of gas into two, so a lower pressure favours it too (Le Chatelier's principle). The pair with a catalyst is tempting because raising the temperature is right, but a catalyst does not shift an equilibrium at all.
Which of the following compounds is an ester?
Answer: C
CH₃COOCH₂CH₃ (ethyl ethanoate) has the ester group –COO– with a carbon chain on both sides, formed from ethanoic acid and ethanol. CH₃CH₂COOH also contains –COO–, but with a hydrogen on the oxygen, which makes it a carboxylic acid (propanoic acid); the others are a ketone and an ether.
What is the IUPAC name of the alcohol CH₃CH(CH₃)CH₂CH₂OH?
Answer: B
The longest chain containing the –OH carbon has four carbons, numbered from the end nearer the –OH group: C1 carries the OH and the methyl branch sits on C3, giving 3-methylbutan-1-ol. Numbering from the other end (2-methylbutan-4-ol) gives the functional group a higher number than necessary, which IUPAC rules forbid.
How many structurally isomeric ALCOHOLS have the molecular formula C₄H₁₀O? (Count structural isomers only, not stereoisomers.)
Answer: A
On the straight chain the –OH can sit on an end carbon (butan-1-ol) or an inner one (butan-2-ol); on the branched chain it can sit on a CH₂ (2-methylpropan-1-ol) or on the central carbon (2-methylpropan-2-ol), making four. Seven is the total for C₄H₁₀O, but it includes the three ethers, which are not alcohols.
Which alcohol is oxidised by warm acidified potassium dichromate(VI) to a ketone?
Answer: D
Propan-2-ol is a secondary alcohol, and oxidising a secondary alcohol gives a ketone, here propanone. Propan-1-ol and ethanol are primary alcohols, which give aldehydes and then carboxylic acids; 2-methylpropan-2-ol is tertiary, with no hydrogen on the –OH carbon, so it resists oxidation under these conditions.
Bromine water is shaken separately with each of the following liquids at room temperature in the dark. Which one decolourises it quickly?
Answer: B
Cyclohexene has a C=C double bond, and bromine adds across it rapidly, giving colourless 1,2-dibromocyclohexane. Benzene is the tempting answer because it is unsaturated, but its delocalised ring of electrons is stable, so it does not undergo addition with bromine water; the two alkanes react with bromine only in light.
Maltose is a disaccharide made of two glucose units. Which bond joins them, and how is it broken during digestion?
Answer: C
In maltose carbon 1 of one α-glucose is linked through an oxygen to carbon 4 of the next, an α-1,4-glycosidic bond formed by condensation, and digestion splits it by adding water back (hydrolysis, catalysed by maltase). β-1,4 links are the bonds of cellulose, which human enzymes cannot hydrolyse; peptide bonds join amino acids, not sugars.
An enzyme is heated to 70 °C and loses its activity permanently. Which level of its structure is still intact?
Answer: A
Heat denaturation breaks the weak interactions (hydrogen bonds, ionic and hydrophobic interactions) that hold the folded shape, but not the covalent peptide bonds, so the sequence of amino acids, the primary structure, survives. The secondary structure is tempting because it is the simplest folding, but α-helices and β-sheets are held by hydrogen bonds and unfold too.
Section 2 of 3
25 questions
Which of the following is true of all viruses?
Answer: C
Viruses are acellular particles with no metabolism of their own, so they can only be copied by the machinery of a host cell they have infected. They have no ribosomes, and each virus carries either DNA or RNA as its genome, never both. Some viruses do have a lipid envelope taken from the host membrane, but many (such as adenoviruses) are naked capsids, so an envelope is not universal.
Plasmodium, the parasite that causes malaria, is a protozoan that has no flagella, cilia or pseudopodia in its adult stages and spends part of its life cycle inside human red blood cells. To which group of protozoa does it belong?
Answer: A
Plasmodium is a sporozoan: an obligate parasite without locomotory organelles in its adult stages, reproducing by multiple fission inside host cells. Flagellata is the tempting choice because Trypanosoma and Giardia are also blood or gut parasites, but they move by flagella; Rhizopoda (such as Entamoeba) move by pseudopodia and Ciliata (such as Paramecium) by cilia.
In deuterostome development the blastopore of the embryo becomes the anus, and the mouth forms later as a second opening. Which of the following animals is a deuterostome?
Answer: D
Echinoderms such as the starfish are deuterostomes, which is why they are more closely related to chordates, including humans, than to most other invertebrates. Annelids (the earthworm), molluscs (the snail) and arthropods (the crab) are all protostomes, in which the blastopore becomes the mouth. The radial symmetry of an adult starfish is misleading: its larva is bilateral and its embryo develops in the deuterostome way.
Which pair of features is characteristic of Cnidaria, such as Hydra and jellyfish?
Answer: B
Cnidarians are radially symmetrical, diploblastic animals whose sac-like gut has one opening, and they catch prey with stinging cells that give the phylum its name. Bilateral symmetry with flame cells describes flatworms (Platyhelminthes), which are tempting because they also have a gut with a single opening. Jointed appendages belong to arthropods, and a true coelom with three germ layers to annelids, molluscs and more complex animals.
Which structure is found in plant cells but not in animal cells?
Answer: B
Plant cells are surrounded by a cellulose cell wall outside the plasma membrane, which gives them their fixed shape and resists bursting in water; animal cells have no wall. Mitochondria are the tempting choice for students who link them with animals and chloroplasts with plants, but plant cells respire too and contain mitochondria, as well as ribosomes and a Golgi apparatus.
A species has a diploid chromosome number of 2n = 8. Ignoring crossing over, how many genetically different combinations of chromosomes can its gametes receive through independent assortment alone?
Answer: C
2n = 8 means four homologous pairs, and in meiosis I each pair lines up independently, so a gamete can receive either member of each pair: 2⁴ = 16 combinations. Answering 8 confuses the number of chromosomes with the number of pairs, and 4 is just the number of pairs. Crossing over would add far more variation, which is why the question excludes it.
A pancreatic cell makes a digestive enzyme and secretes it. Which route does the protein take from its synthesis to its release from the cell?
Answer: A
Secreted proteins are made on ribosomes bound to the rough endoplasmic reticulum, modified and packaged in the Golgi apparatus, and carried in secretory vesicles that fuse with the plasma membrane (exocytosis). Lysosomes are an end destination for hydrolytic enzymes kept inside the cell, not a stage on the way out, and the Golgi always comes after the endoplasmic reticulum, not before it.
During intense exercise, human muscle cells short of oxygen convert pyruvate into lactate. What is the main benefit of this reaction to the cell?
Answer: D
Glycolysis reduces NAD⁺ to NADH; without oxygen the electron transport chain cannot reoxidise it, so pyruvate is reduced to lactate to regenerate NAD⁺ and keep glycolysis, with its net 2 ATP per glucose, running. The conversion itself makes no ATP, which is the common misconception. Lactic acid fermentation releases no carbon dioxide; that is a feature of alcoholic fermentation in yeast.
The rate of an enzyme-catalysed reaction is measured at increasing substrate concentrations, first without and then with a fixed concentration of a competitive inhibitor. Which statement correctly describes the effect of the inhibitor?
Answer: C
A competitive inhibitor resembles the substrate and competes for the active site, so at high substrate concentration the substrate outcompetes it and the same maximum rate is approached. A permanently lowered maximum rate, and binding away from the active site, describe non-competitive inhibition, which is the usual confusion. Denaturation is caused by heat or extreme pH, not by an inhibitor binding reversibly.
Where does the oxygen released by a green plant during photosynthesis come from?
Answer: A
Light energy absorbed by photosystem II drives the splitting of water (photolysis) on the thylakoid membranes, releasing O₂ and supplying electrons and protons. Carbon dioxide is the tempting answer because it contains oxygen, but its carbon and oxygen are built into sugar in the Calvin cycle; experiments with water labelled with ¹⁸O show the released oxygen comes from water.
Which type of RNA carries an anticodon and brings a specific amino acid to the ribosome during translation?
Answer: B
Each tRNA carries an amino acid at one end and, in its anticodon loop, three bases that pair with a complementary codon on the mRNA, so the right amino acid is added in the right place. mRNA carries the codons, not anticodons; rRNA forms the structure and catalytic core of the ribosome; and an RNA primer only starts DNA synthesis.
In a plant, tall (T) is dominant to short (t) and purple flowers (P) are dominant to white (p); the two genes are on different chromosomes. A plant heterozygous for both genes (TtPp) is test-crossed with a short, white-flowered plant (ttpp). What proportion of the offspring are expected to be short with white flowers?
Answer: D
The heterozygote makes four gamete types, TP, Tp, tP and tp, in equal numbers, and the ttpp parent contributes only tp, so the offspring show four phenotypes in a 1 : 1 : 1 : 1 ratio and short white is 1/4. The answer 1/16 is the proportion of double recessives from crossing two double heterozygotes (TtPp × TtPp), not from a test cross.
Two genes, A and B, lie on the same chromosome, 10 map units (centimorgans) apart. A plant heterozygous for both, with A and B on one chromosome and a and b on its homologue, is test-crossed with an aabb plant. What percentage of the offspring are expected to show a recombinant combination of characters?
Answer: D
A map distance of 10 units means crossing over separates the two genes in 10% of gametes, so 10% of the heterozygote's gametes are recombinant (Ab or aB), and in a test cross each gamete shows directly in the offspring's phenotype. 50% recombinants would mean the genes assort independently, as genes on different chromosomes do; 90% is the share of parental-type offspring, and 5% is the share of each of the two recombinant classes, not of both together.
An autosomal recessive condition affects 1 in 400 people in a large, randomly mating population in Hardy–Weinberg equilibrium. Approximately what percentage of the population are unaffected carriers?
Answer: A
Affected people are q² = 1/400, so q = 1/20 = 0.05 and p = 0.95; carriers are 2pq = 2 × 0.95 × 0.05 = 0.095, or 9.5%. The value 5% is the frequency of the recessive allele itself, not of carriers, and 90.25% is p², the proportion of homozygous dominant people.
Bacteria are grown for many generations on a medium containing only heavy nitrogen (¹⁵N), then transferred to a medium containing only light nitrogen (¹⁴N). After exactly two rounds of DNA replication in the ¹⁴N medium, what is the composition of the DNA molecules?
Answer: C
Replication is semi-conservative: after one round every molecule is hybrid, and in the second round each hybrid separates into one ¹⁵N strand and one ¹⁴N strand, each paired with a new ¹⁴N strand, giving two hybrid and two light molecules. 'All hybrid' is the result after only one round. No fully heavy molecule can survive, because each original heavy strand is always paired with a new light one.
Which observation about mitochondria supports the endosymbiotic theory of their origin?
Answer: B
The theory holds that mitochondria descend from free-living aerobic bacteria engulfed by an ancestral cell, and they still carry circular, histone-free DNA and 70S-type ribosomes like bacteria, and divide by fission. They have a double membrane, not a single one, consistent with engulfment, and they arise only from existing mitochondria, never from the Golgi apparatus.
In a food chain, the producers fix 20,000 kJ of energy per m² per year. Assuming that about 10% of the energy at each trophic level passes to the next, how much energy per m² per year reaches the tertiary consumers?
Answer: A
Each transfer keeps about a tenth: primary consumers receive 2,000 kJ, secondary consumers 200 kJ and tertiary consumers 20 kJ. The answer 200 kJ stops one level short, a common slip from counting the producers as the first consumer level. The rest is lost mainly as heat from respiration and in material that is not eaten or not digested.
Homologous structures share a common evolutionary origin even if they now do different jobs. Which pair are homologous?
Answer: C
The whale's flipper and the human arm are both built on the same pentadactyl limb plan, with the same bones inherited from a common ancestor, even though one swims and the other grasps. The bird and butterfly wings, the octopus and human eyes, and the two kinds of spines are analogous: they look or work alike because of similar selection pressures, but evolved independently from different structures.
A patient with blood group A, Rh-negative, needs a transfusion of red blood cells. Which donor's red cells can safely be given?
Answer: D
The patient's plasma contains anti-B antibodies, so donor cells must carry no B antigen, and as an Rh-negative person the patient should not receive the D antigen either; group O Rh-negative cells carry neither A, B nor D antigens. Group A Rh-positive matches the ABO group but would expose the patient to the D antigen and could sensitise them. Group AB and group B cells carry the B antigen and would be agglutinated.
In which situation is a baby at greatest risk of haemolytic disease of the newborn caused by Rhesus (anti-D) antibodies?
Answer: B
Fetal Rh-positive cells entering the mother's circulation, mostly at delivery, make an Rh-negative mother produce anti-D antibodies; in a later pregnancy these IgG antibodies cross the placenta and destroy an Rh-positive baby's red cells. The first Rh-positive pregnancy is usually spared because sensitisation has not yet happened, which is why anti-D is given to the mother after delivery. An Rh-negative baby carries no D antigen, so it cannot be attacked.
A patient with severe liver failure has a very low concentration of albumin in the blood plasma and develops swelling of the tissues (oedema). What best explains the oedema?
Answer: A
Tissue fluid forms at the arterial end of a capillary where hydrostatic pressure exceeds the oncotic pressure of the plasma proteins, and most of it returns at the venous end where oncotic pressure is the larger. Albumin provides most of that oncotic pressure, so with little albumin less fluid returns and more stays in the tissues. Albumin does not raise blood hydrostatic pressure, and the problem is the opposite of lymph removing fluid: the lymph cannot drain the excess.
Which statement about bile is correct?
Answer: C
Bile is produced continuously by the liver, stored and concentrated in the gall bladder, and its bile salts break fat into small droplets so that pancreatic lipase can act on a larger surface. The gall bladder only stores bile, and lipase comes from the pancreas, so it is not an ingredient of bile. Bile also helps neutralise acid from the stomach, but it does not digest protein.
Glucose is filtered freely in the glomerulus, yet the urine of a healthy person contains almost none. In a person with uncontrolled diabetes mellitus, glucose appears in the urine. Why?
Answer: D
Normally all filtered glucose is reabsorbed in the proximal convoluted tubule by co-transport with Na⁺, but these carriers have a maximum rate; when blood glucose is very high, more glucose is filtered than they can carry and the excess passes into the urine. Glucose is filtered in healthy people too, so filtration starting is not the explanation, and glucose reabsorption does not happen in the loop of Henle or depend on ADH.
Which part of the human brain coordinates balance, posture and the precision of voluntary movements?
Answer: B
The cerebellum compares the movement the motor cortex intends with information from the muscles, joints and vestibular apparatus, and smooths and corrects it, which is why damage to it causes unsteadiness and clumsy movement. The medulla oblongata is tempting because it controls vital automatic functions such as breathing and heart rate, but not coordination; the hypothalamus regulates homeostasis and the pituitary, and the thalamus relays sensory information to the cortex.
What causes the rapid depolarisation of a neuron's membrane during the rising phase of an action potential?
Answer: A
When the threshold is reached, voltage-gated sodium channels open and Na⁺ rushes in down its concentration and electrical gradient, making the inside of the membrane positive. Potassium channels open slightly later and K⁺ flows out, not in, causing repolarisation. The Na⁺/K⁺ pump maintains the resting gradients and works continuously; it does not produce the action potential.
Section 3 of 3
25 questions
A skin wound has an area of 3.5 cm². What is this area in m²?
Answer: C
1 cm = 10⁻² m, so 1 cm² = (10⁻²)² m² = 10⁻⁴ m², and 3.5 cm² = 3.5 × 10⁻⁴ m². The tempting 3.5 × 10⁻² m² converts the length factor but forgets that an area unit squares it.
The sides of a rectangular gel are measured as 4.20 cm and 1.5 cm. What is its area, given to the precision the measurements justify?
Answer: A
4.20 × 1.5 = 6.30, but a product can carry no more significant figures than its least precise factor, and 1.5 has only two, so the area is 6.3 cm². Writing 6.30 cm² claims three significant figures, a precision the 1.5 cm measurement does not have.
At high speed, the air-resistance force on a cyclist is modelled as F = k·v², where F is in newtons and v in m/s. What are the SI units of the constant k?
Answer: D
k = F/v², and a newton is kg·m/s², so k has units (kg·m/s²) ÷ (m²/s²) = kg/m. The answer kg/s is what k would have in the linear model F = k·v, where only one power of speed is divided out.
In a region, the proportion of children vaccinated against measles rose from 40% to 50% in one year. Which statement is correct?
Answer: B
The difference between two percentages, 50 − 40, is 10 percentage points; relative to the starting value it is 10/40 = 25%. Saying it 'rose by 10%' mixes the two up: a 10% rise from 40% would give only 44%.
An antibiotic is prescribed at 15 mg per kg of body mass per day, given as three equal doses a day. How much is each dose for a child of 24 kg?
Answer: B
The daily amount is 15 mg/kg × 24 kg = 360 mg, and split into three equal doses that is 120 mg each. 360 mg is the whole day's amount, not a single dose.
A solid cube of a material with side 2 cm has a mass of 24 g. What is the mass of a solid cube of the same material with side 6 cm?
Answer: D
Mass scales with volume, and volume scales with the cube of the length: tripling the side multiplies the volume by 3³ = 27, so the mass is 24 g × 27 = 648 g. 216 g scales by the area factor 3² = 9, and 72 g by the length factor alone.
A pie chart shows a hospital's 80 tonnes of waste in one year: general waste 55%, recyclable waste 25%, infectious clinical waste 15%, sharps and pharmaceutical waste 5%. How many tonnes of infectious clinical waste were produced?
Answer: A
15% of 80 t is 0.15 × 80 = 12 t. Answering 15 t reads the percentage off the chart as if it were already a mass; 20 t is the recyclable share.
A straight-line graph passes through the points (1, 5) and (4, 14). Which equation describes the line?
Answer: C
The gradient is (14 − 5)/(4 − 1) = 9/3 = 3, and putting (1, 5) into y = 3x + c gives c = 2, so y = 3x + 2; check: 3 × 4 + 2 = 14. The equation y = 2x + 3 also passes through (1, 5) but gives 11, not 14, at x = 4 — always test both points.
A calibration graph of absorbance (vertical axis) against glucose concentration in mmol/L (horizontal axis) is a straight line through the origin, with an absorbance of 0.60 at 4.0 mmol/L. A patient sample gives an absorbance of 0.27. What is its glucose concentration?
Answer: A
The gradient is 0.60/4.0 = 0.15 absorbance units per mmol/L, so the concentration is 0.27/0.15 = 1.8 mmol/L. Multiplying 0.27 by the gradient instead of dividing (giving 0.041) is the axis trap: the gradient converts concentration into absorbance, so going back means dividing by it.
A radioactive tracer has a half-life of 6 hours. A patient is injected with a dose of activity 800 MBq at 08:00. What is the activity of the tracer at 02:00 the next morning, ignoring its excretion?
Answer: D
From 08:00 to 02:00 the next day is 18 hours, which is three half-lives, so the activity is 800 × (½)³ = 100 MBq. 267 MBq treats the decay as linear (losing a third each 6 hours), but each half-life halves whatever is left.
A bacterial culture grows from 5 × 10³ cells to 1.6 × 10⁵ cells in 2.5 hours, doubling at a constant rate. What is its doubling time?
Answer: B
The count has risen by a factor of 1.6 × 10⁵ / 5 × 10³ = 32 = 2⁵, so five doublings took 150 minutes, i.e. 30 minutes each. 37.5 minutes comes from counting only four doublings; 4.7 minutes divides the time by the growth factor 32 rather than by the number of doublings.
Five resting heart-rate readings (beats per minute) are: 62, 70, 64, 78, 66. What is their mean?
Answer: C
The sum is 62 + 70 + 64 + 78 + 66 = 340, and 340/5 = 68. The value 66 is the median (the middle value once sorted), and 70 is the midpoint of the smallest and largest readings, neither of which is the mean.
In a population, blood haemoglobin concentration is normally distributed with a mean of 140 g/L and a standard deviation of 10 g/L. Approximately what percentage of the population has a value above 160 g/L?
Answer: C
160 g/L is two standard deviations above the mean; about 95% of values lie within two standard deviations, leaving 5% outside, split equally between the two tails, so about 2.5% lie above 160 g/L. Answering 5% forgets that half of the outside 5% lies below 120 g/L.
An observational study of 2000 adults finds a correlation of r = +0.35 between daily coffee consumption and lung cancer (p = 0.002). In the same sample, smokers drink more coffee than non-smokers. Which conclusion is the most appropriate?
Answer: A
A small p-value says the association would rarely arise by chance alone, but an observational study cannot separate cause from confounding, and smoking is linked both to coffee drinking and to lung cancer. The p-value measures evidence against chance, not strength: r = +0.35 is only a weak-to-moderate positive correlation.
An ambulance covers 18 km in 12 minutes. What is its average speed?
Answer: D
18 000 m ÷ (12 × 60 s) = 18 000/720 = 25 m/s (equivalently 18 km in 0.2 h is 90 km/h, and 90 ÷ 3.6 = 25 m/s). 90 m/s keeps the number for km/h but swaps in the wrong unit.
A car of mass 1000 kg travelling at 20 m/s brakes uniformly to rest over a distance of 40 m. What is the average braking force?
Answer: B
The kinetic energy removed is ½ × 1000 × 20² = 200 000 J, and work = force × distance, so F = 200 000/40 = 5000 N. 10 000 N comes from forgetting the ½ in ½mv².
A child of mass 30 kg starts from rest at the top of a slide 5 m high and reaches the bottom at 8 m/s. How much energy was transferred to heat by friction on the way down? (g = 10 m/s²)
Answer: A
The potential energy lost is mgh = 30 × 10 × 5 = 1500 J, and the kinetic energy gained is ½ × 30 × 8² = 960 J; the difference, 1500 − 960 = 540 J, went to friction. 960 J is the kinetic energy at the bottom, which is what was kept, not what was lost.
A hospital lift and its passengers have a total mass of 600 kg. The motor raises them 20 m at constant speed in 15 s. What useful power does the motor deliver? (g = 10 m/s²)
Answer: D
At constant speed the motor's force equals the weight, 600 × 10 = 6000 N, so the work done is 6000 × 20 = 120 000 J and the power is 120 000/15 = 8000 W = 8 kW. 800 W leaves out g, using the mass instead of the weight.
A wooden block of volume 500 cm³ and density 600 kg/m³ floats in water of density 1000 kg/m³. What volume of the block is below the water surface?
Answer: C
A floating object displaces its own weight of fluid, so the submerged fraction equals the density ratio, 600/1000 = 0.6, and 0.6 × 500 cm³ = 300 cm³. 200 cm³ is the volume above the surface, not below it.
A simple pendulum has a period of 2.0 s on Earth. Its string is made four times as long and it is taken to a planet where the gravitational acceleration is four times that on Earth. What is its new period?
Answer: B
The period is T = 2π√(L/g), so it depends only on the ratio L/g; multiplying both L and g by four leaves L/g, and so the period, unchanged at 2.0 s. 4.0 s accounts only for the longer string (√4 = 2) and ignores the stronger gravity, which shortens the period by the same factor.
Ultrasound travels through soft tissue at 1540 m/s. What is the wavelength of 2 MHz ultrasound in soft tissue?
Answer: A
λ = v/f = 1540/(2 × 10⁶) = 7.7 × 10⁻⁴ m = 0.77 mm. 3.1 × 10⁹ m multiplies speed by frequency instead of dividing, which a quick unit check rules out.
A 6 Ω resistor and a 3 Ω resistor are connected in parallel across a 6 V battery of negligible internal resistance. What current flows from the battery?
Answer: D
For resistors in parallel, 1/R = 1/6 + 1/3 = 1/2, so R = 2 Ω and I = V/R = 6/2 = 3 A (1 A through the 6 Ω resistor plus 2 A through the 3 Ω one). 0.67 A treats the resistors as if in series, 9 Ω in total, but a parallel combination is always lower than its smallest resistor.
Which list puts these kinds of electromagnetic radiation in order of increasing photon energy?
Answer: B
Photon energy rises with frequency, so it increases as the wavelength gets shorter: radio waves, then visible light, then ultraviolet, then X-rays. The list starting with X-rays is the same sequence reversed, which is the order of increasing wavelength, not energy.
In a sample of double-stranded DNA, 18% of the bases are thymine. What percentage of the bases are guanine?
Answer: C
Thymine pairs with adenine, so adenine is also 18% and A + T = 36%; the remaining 64% is G + C in equal amounts, so guanine is 32%. 64% is guanine and cytosine together.
A urine culture is diluted by a total factor of 10⁵, and 0.1 cm³ of the diluted sample is spread on an agar plate. After incubation, 46 colonies are counted. How many colony-forming units (CFU) were in each cm³ of the original sample?
Answer: A
46 colonies in 0.1 cm³ means 460 CFU per cm³ of the diluted sample, and undoing the 10⁵ dilution gives 460 × 10⁵ = 4.6 × 10⁷ CFU/cm³. 4.6 × 10⁶ CFU/cm³ forgets that only 0.1 cm³, not 1 cm³, was plated.
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LF1 publishes no past papers, but its How to prepare page links an official mock test as a free PDF: 75 questions, 25 each in Chemistry, Biology and General Science, with the answer key on its last page, and a separate General Science mock with the correct options marked. It is the official picture of the paper: the four-option format on this page was confirmed on it. The practice paper on this page is IvyTest's own: all 75 questions in LF1's format, each with its answer explained, which the official key does not do.
This paper keeps the format LF1 states for 2027/28 (75 single-best-answer questions with four options, 25 per part, no deduction for a wrong answer) and the kinds of question its mock asks, including General Science, for which LF1 publishes no syllabus: units, proportions, graphs, statistics and physics-style problems. Every question is new.
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