KMU MDCAT 2025 PAPER

Explanation:

Semilunar valves open when ventricular pressure becomes higher than the pressure in aorta/pulmonary artery.
This happens in ventricular systole, especially during the ejection phase.
Their opening allows blood to leave the ventricles into the great arteries.

Explanation:

AV node slows down conduction for a short time.
This delay lets atria finish pushing blood into ventricles first.
Then the impulse passes to bundle branches and Purkinje fibres for ventricular contraction.

Explanation:

“LUB” (S1) happens at the start of ventricular systole.
Rising ventricular pressure snaps the mitral and tricuspid valves shut.
This valve closure produces the first heart sound.

Explanation:

Fluid leaks out of blood capillaries into tissues and becomes interstitial fluid.
Lymph vessels collect the excess fluid and return it to the blood circulation.
This prevents tissue swelling (edema) and maintains normal fluid balance.

Explanation:

Helper T cells coordinate the immune response by releasing cytokines.
They stimulate B cells to produce antibodies and support cytotoxic T-cell activation.
So they act as “controllers” that boost and organize immune defenses.

Explanation:

IRV is the extra air you can breathe in after a normal quiet inspiration.
It is not the leftover air after forced expiration (that is residual volume).
It is also not normal breathing air (that is tidal volume).

Explanation:

Third line defense is the adaptive immune response (B cells and T cells).
It recognizes a specific antigen and makes a targeted response against it.
It also forms memory cells, so the same infection is handled faster next time.

Explanation:

Carbonic anhydrase speeds up the reaction:
CO₂ + H₂O ⇌ carbonic acid (H₂CO₃).
This helps transport CO₂ in blood mainly as bicarbonate ions.
So its direct role is linking CO₂ with water rapidly.

Explanation:

External intercostals lift the ribs up and outward during inspiration.
This increases the chest cavity volume and lowers the air pressure inside lungs.
Air then moves into the lungs because pressure outside is higher.

Explanation:

Smoking (especially tar and toxic gases) damages alveolar walls and reduces elasticity.
This decreases the surface area available for diffusion of O₂ and CO₂.
As a result, gaseous exchange becomes inefficient and breathing capacity falls over time.

Explanation:

Intrinsic factor binds vitamin B12 in the stomach and protects it from digestion.
This complex is required for B12 absorption in the ileum.
Without intrinsic factor, B12 absorption fails and megaloblastic (pernicious) anemia can occur.

Explanation:

Delta (D) cells release somatostatin, which acts as an “inhibitory” hormone.
It reduces secretion of both insulin and glucagon to stabilize blood glucose changes.
So it fine-tunes pancreatic hormone output and prevents sudden fluctuations.

Explanation:

Duodenum is the first part of small intestine where major chemical digestion begins.
It receives bile and pancreatic enzymes to digest fats, proteins, and carbohydrates.
Bicarbonate also neutralizes acidic chyme to provide a suitable pH for enzymes.

Explanation:

During the pharyngeal stage, swallowing becomes reflex and airway protection occurs.
The epiglottis covers the glottis and the larynx elevates, blocking the trachea.
This ensures the bolus moves into the esophagus instead of entering the lungs.

Explanation:

Juxtamedullary nephrons have long loops of Henle that go deep into the medulla.
They create and maintain the medullary osmotic gradient by the countercurrent multiplier system.
This gradient is essential for concentrating urine by allowing more water reabsorption.

Explanation:

DCT helps regulate pH by secreting H⁺ into the tubular fluid.
Removing H⁺ from blood reduces acidity and maintains normal blood pH.
At the same time, bicarbonate is conserved/reabsorbed to support buffering.

Explanation:

Aldosterone increases Na⁺ reabsorption in DCT and collecting duct.
It stimulates Na⁺ channels and Na⁺/K⁺-ATPase activity, so sodium is retained and potassium is secreted.
This helps maintain blood volume and blood pressure.

Explanation:

Excess water lowers blood osmolarity, so ADH secretion drops.
With less ADH, collecting ducts become less permeable to water.
Less water is reabsorbed, so kidneys produce a larger volume of dilute urine.

Explanation:

Glomerular capillaries are designed for ultrafiltration under high blood pressure.
Water and small solutes pass into Bowman’s capsule to form the glomerular filtrate.
Reabsorption and secretion mainly happen later in the renal tubules, not in glomerulus.

Explanation:

When body temperature rises, hypothalamus activates heat-loss mechanisms.
Skin blood vessels dilate to send more warm blood to the surface.
Sweating increases, and evaporation removes heat to cool the body.

Explanation:

Uric acid is poorly soluble in water compared to urea and ammonia.
That is why it can crystallize easily and form urate crystals or stones.
Ammonia is highly soluble but very toxic, so most humans do not excrete it directly.

Explanation:

Humans convert toxic ammonia into urea in the liver (urea cycle).
Urea is less toxic and can be excreted with moderate water loss.
So the main nitrogenous waste in humans is urea.

Explanation:

Excess PTH raises blood calcium levels by increasing bone resorption and renal calcium handling.
Higher calcium load in urine increases the chance of calcium salt stone formation.
So hyperparathyroidism commonly predisposes to calcium-based stones like calcium phosphate.

Explanation:

Monoclonal antibodies are produced by forming hybridoma cells through cell fusion.
Antibody-producing B-lymphocytes (commonly taken from spleen) are fused with an immortal myeloma-type cell line.
The hybridoma can divide continuously and secrete one specific antibody.

Explanation:

A DNA probe is a short, labeled single-stranded nucleic acid sequence.
It pairs with its complementary target sequence by base pairing (hybridization).
This binding helps detect the presence of a particular gene or pathogen sequence.

Explanation:

“Monoclonal” means produced from one clone of immune cells.
Because all cells come from a single original cell, they make identical antibodies.
So the antibodies have the same specificity and bind the same antigen epitope.

Explanation:

In gene therapy, a normal gene must be delivered into target cells.
A vector (often a modified virus) carries and inserts the gene into the patient’s cells.
This helps restore the correct genetic instruction and improve cell function.

Explanation:

DNA follows complementary base pairing rules.
Cytosine forms three hydrogen bonds with guanine, making a strong pair.
This pairing maintains uniform DNA width and accurate replication.

Explanation:

Fatty acids are broken down by beta-oxidation into many acetyl-CoA molecules.
Each acetyl-CoA enters Krebs cycle and produces a large yield of ATP via electron transport chain.
Fats are energy-dense because they are more reduced and release more energy on oxidation.

Explanation:

A synapse is the functional junction between a presynaptic neuron and a postsynaptic cell.
Neurotransmitters are released from axon terminal into the synaptic cleft.
They bind receptors on the next neuron and start a new nerve impulse.

Explanation:

Golgi apparatus modifies, sorts, and packages proteins and lipids for secretion or transport.
It also contributes to membrane formation and forms lysosomes by packaging enzymes.
Cellular respiration is carried out mainly by mitochondria, not Golgi bodies.

Explanation:

At resting potential, Na⁺ concentration is higher outside the neuron, while K⁺ is higher inside.
The Na⁺/K⁺ pump maintains this gradient by pumping Na⁺ out and K⁺ in.
This ionic imbalance helps keep the inside of the neuron relatively negative.

Explanation:

HIV spreads through infected blood, semen, vaginal fluids, and from mother to child in some cases.
Sharing needles and contaminated transfusions can directly transfer infected blood.
Casual contact like handshakes does not transmit HIV because the virus is not spread by touch.

Explanation:

Smooth ER contains enzyme systems that detoxify drugs and harmful chemicals.
This function is especially prominent in liver cells where detoxification demand is high.
Lysosomes digest cellular waste, ribosomes make proteins, and mitochondria produce ATP.

Explanation:

The active site is the specific region on an enzyme where the substrate attaches.
Binding forms the enzyme–substrate complex, allowing the reaction to proceed efficiently.
Its shape and chemical properties give enzymes their specificity for particular substrates.

Explanation:

Lamarck proposed that traits developed during an organism’s lifetime could be passed to offspring.
This is often explained using “use and disuse” of organs leading to trait development.
Darwinism focuses on natural selection, while biogenesis is about life from pre-existing life.

Explanation:

Influenza virus has a lipid envelope around its capsid.
This envelope contains surface proteins that help the virus attach and enter host cells.
Polio and Hepatitis A are non-enveloped viruses, while leaf curl is typically linked with plant viruses (often DNA viruses).

Explanation:

Glycoproteins are membrane proteins with carbohydrate chains attached.
They form part of the glycocalyx and help in cell recognition, signaling, and adhesion.
Therefore, they are most commonly associated with the plasma membrane surface.

Explanation:

Nuclear pores are protein channels in the nuclear envelope.
They allow controlled movement of RNA, proteins, and other molecules between nucleus and cytoplasm.
Plasma membrane controls cell boundary, while lysosomes and mitochondria have different roles.

Explanation:

Hydrogen bonds form a strong network between water molecules.
A lot of heat is used to break these bonds before temperature can rise.
That is why water warms up and cools down slowly compared to many liquids.

Explanation:

Centromere is the narrowed region where kinetochore forms.
Spindle fibers attach to kinetochore to pull sister chromatids apart during division.
Telomeres are chromosome ends; chromatin and nucleosomes are DNA packaging forms.

Explanation:

Sensory (afferent) neurons carry impulses from receptors to CNS.
Pain receptors in skin generate impulses that travel via sensory neurons to spinal cord/brain.
Motor neurons carry commands from CNS to muscles, not sensory information.

Explanation:

Haploid cells (n) contain one set of chromosomes.
Normal body cells are diploid (2n), meaning they have two sets.
So haploid number is exactly half of the diploid number.

Explanation:

Glycogen is the storage carbohydrate in animals, mainly in liver and muscles.
It is highly branched, so glucose can be released quickly when needed.
Cellulose and chitin are structural polysaccharides, and amylose is mostly unbranched.

Explanation:

Non-competitive inhibitors bind at a site other than the active site (allosteric site).
This changes enzyme shape or function, so activity decreases even if substrate is present.
Competitive inhibitors bind the active site, while cofactors help enzymes work.

Explanation:

Influenza virus (Orthomyxovirus) has an outer lipid envelope taken from the host cell membrane, with viral spikes (HA and NA) on it. So, morphologically it is an enveloped virus.

• Enveloped viruses → have a lipid covering (envelope) outside the capsid

• Non-enveloped viruses → no lipid envelope, only protein capsid

Explanation:

Globular proteins are compact and usually soluble, like enzymes, albumin, and hemoglobin.
Collagen is a fibrous protein with long, rope-like structure.
Fibrous proteins are mainly structural and not typically soluble.

Explanation:

At rest, a neuron has a potential difference across its membrane (inside negative).
This condition is called polarization because charges are separated.
Depolarization occurs during impulse, and repolarization restores resting state afterward.

Explanation:

A nerve impulse is an action potential produced by movement of ions (Na⁺ and K⁺) across the membrane.
This creates an electrical change, and it spreads along the axon as a wave.
Because it involves both electrical change and chemical ion movement, it is electrochemical.

Explanation:

Reticular formation is a network of neurons mainly present in the brainstem.
Brainstem includes medulla and pons (hindbrain) and midbrain.
It helps in alertness, sleep-wake control, and basic vital functions.

Explanation:

Enzymes provide an alternative reaction pathway with lower activation energy.
This allows more reactant molecules to reach the transition state quickly.
So the reaction rate increases without changing the final products.

Explanation:

Glucose is directly absorbed and rapidly raises blood sugar.
Sucrose is digested into glucose and fructose; the glucose component raises blood sugar too.
So both can increase blood glucose levels and are restricted in diabetes.

Explanation:

Medulla oblongata controls vital involuntary activities like breathing and heart rate.
Memory is mainly linked to cerebrum/hippocampus, not pons.
Balance is mainly cerebellum, and dreaming is associated with sleep centers and cerebral cortex activity.

Explanation:

If cells released food energy in one step, most of it would be lost as heat.
Cells capture energy in small, controlled steps by making ATP.
ATP stores usable energy for cellular work, preventing excessive heat loss and damage.

Explanation:

Cohesion keeps water molecules together, helping continuous water columns form.
Adhesion helps water stick to vessel walls, supporting upward movement in narrow tubes.
These together make water an effective transport fluid in plants and animals.

Explanation:

Lamarckism proposed that acquired traits (like tail removal) can be inherited.
But cutting tails does not change genes in reproductive cells.
So offspring still inherit normal tail genes and are born with tails.

Explanation:

Phospholipids form a bilayer in water-based environments.
Hydrophilic heads face the watery cytoplasm and extracellular fluid.
Hydrophobic tails avoid water and face inward toward each other inside the bilayer.

Explanation:

RNA contains ribose sugar, not deoxyribose, and it is usually single stranded, not double.
RNA has four nucleotides, but it uses uracil (U) instead of thymine (T).
So the distinguishing feature given here is the presence of uracil in RNA.

Explanation:

Purines (A, G) are larger double-ring bases, while pyrimidines (C, T) are smaller single-ring bases.
Pairing one large base with one small base keeps DNA width uniform.
So A pairs with T and G pairs with C, maintaining constant diameter.

Explanation:

Ribose has 5 carbons, so it is a pentose sugar.
It is an aldose (contains an aldehyde group in its open-chain form).
Ribulose is a ketopentose, and galactose is an aldohexose, not a ketose.

Explanation:

A stimulus is detected by a receptor and carried to CNS by the sensory (afferent) neuron.
In spinal cord, interneuron (associative neuron) relays the impulse.
Motor (efferent) neuron carries the command to the effector to produce response.

Explanation:

Fertilization usually occurs in the ampulla region of the fallopian tube.
Sperm meets the ovum there soon after ovulation.
The zygote then travels to the uterus for implantation later.

Explanation:

Non-ciliated (secretory/peg) cells of the oviduct produce nourishing secretions.
These secretions moisten the tube and support ovum and early embryo.
Ciliated cells mainly help move the ovum toward the uterus by ciliary beating.

Explanation:

Accessory glands add secretions to semen and support sperm function.
These include seminal vesicles, prostate gland, and bulbo-urethral glands.
Testes are primary sex organs that produce sperm and testosterone, not accessory glands.

Explanation:

Syphilis is caused by Treponema pallidum.
This bacterium has a spiral, corkscrew-like shape, so it is a spirochaete.
Its shape helps it move through tissues and spread in the body.

Explanation:

Cartilage is avascular, meaning it has no direct blood supply.
Nutrients diffuse to chondrocytes through the matrix, so healing is slow.
It commonly contains type II collagen and its cells are chondrocytes.

Explanation:

Bone matrix has inorganic salts (mainly calcium phosphate/hydroxyapatite) and organic collagen fibers.
The inorganic part forms the hard, rigid component and is about 65% by weight.
The remaining portion is mainly organic collagen and water, providing flexibility.

Explanation:

Osteoclasts are large multinucleated cells that dissolve bone matrix.
They release acids and enzymes to break down mineral and collagen components.
Osteoblasts build bone, osteocytes maintain it, and chondrocytes belong to cartilage.

Explanation:

Sarcomere is the functional contractile unit of a myofibril.
It lies between two Z-lines and contains actin and myosin filaments.
Shortening of sarcomeres causes muscle contraction.

Explanation:

Skeletal muscle is voluntary, controlled by the somatic nervous system.
Its fibers are long and multinucleated due to fusion of myoblasts during development.
Smooth and cardiac muscles are involuntary, and cardiac fibers usually have 1–2 nuclei.

Explanation:

A-band corresponds to the full length of the myosin (thick) filaments.
In most of the A-band, actin overlaps with myosin during contraction.
I-band has only actin, and H-zone has only myosin (no overlap).

Explanation:

Calcium binds to troponin on the thin filament.
This shifts tropomyosin away from actin’s active sites.
Myosin heads can then attach to actin and contraction begins.

Explanation:

Fibrous joints are joined by dense connective tissue and allow very little or no movement.
Skull sutures are classic fibrous joints that firmly hold cranial bones together.
Shoulder and elbow are synovial joints, while intervertebral discs are cartilaginous joints.

Explanation:

Brown-eye allele is commonly dominant over blue-eye allele in basic Mendelian concept.
A parent with brown eyes may still carry a recessive blue allele (heterozygous).
The child can inherit the dominant brown allele and show brown eyes even if the other parent is blue-eyed.

Explanation:

A 9:3:3:1 phenotypic ratio appears when two genes are on different chromosomes (unlinked).
Each gene pair segregates independently during gamete formation.
This matches Mendel’s law of independent assortment in a standard dihybrid cross.

Explanation:

Crossing over occurs when homologous chromosomes synapse and form bivalents.
This happens in Prophase I, specifically during pachytene stage.
Exchange of chromatid segments creates genetic recombination and variation.

Explanation:

Genes located close on the same chromosome tend to be inherited together as a unit.
So they do not assort independently like genes on different chromosomes.
Crossing over can separate linked genes, but close genes have a lower chance of being separated.

Explanation:

A carrier female has one normal X and one affected X, so she usually does not show the full disorder.
Sons get their single X from the mother; if they inherit the affected X, they become diseased.
Daughters usually become carriers if they inherit the affected X (unless father is also affected).

Explanation:

Hemophilia is classically inherited as an X-linked recessive trait.
It appears more commonly in males because they have only one X chromosome.
Females usually become carriers unless they inherit affected X from both parents.

Explanation:

Mother produces Xᴴ and Xʰ eggs, while father produces Xᴴ and Y sperm.
Sons: XᴴY (normal) or XʰY (hemophiliac) → 50% affected.
Daughters: XᴴXᴴ (normal) or XᴴXʰ (carrier) → none affected;
50% are normal (unaffected non-carrier).

Explanation:

Pericardium is the double-layered sac surrounding the heart.
It protects the heart and reduces friction during beating by pericardial fluid.
Pleura covers lungs, peritoneum covers abdominal organs, and meninges cover brain/spinal cord.

Explanation:

The longest chain has 4 carbons, so parent name is butanone.
The carbonyl group gets priority and is placed at position 2 (butan-2-one).
The bromo substituent is on carbon 1 in the intended structure, so it becomes 1-bromo.

Explanation:

Stoichiometric ratio is 2 mol Na : 1 mol Cl₂.
For 4 mol Na, required Cl₂
= 4/2
= 2 mol.
Given Cl₂ is exactly 2 mol, so nothing is left unreacted.

Explanation:

Neutral Fe = [Ar]4s2 3d6.
On ion formation, electrons are removed from 4s first, then 3d.
Fe3+ loses 2 (from 4s) and 1 (from 3d) → [Ar]3d5.

Explanation:

From ideal gas law,
V ∝ T/P (for fixed n).
If T becomes 2T and P becomes 2P,
then
V ∝ (2T)/(2P).
The factors cancel, so volume remains unchanged.

Explanation:

CH₃(CH₂)₂CCH = CH₃–CH₂–CH₂–C≡CH

• Count the longest chain containing the triple bond:
  CH₃ (1) – CH₂ (2) – CH₂ (3) – C (4) – CH (5) → 5 carbons = pent-

• Number the chain from the end nearest the triple bond (IUPAC rule: multiple bond gets the lowest number):
  From the right side: HC≡C–CH₂–CH₂–CH₃
  Triple bond starts at carbon 1 → pent-1-yne

Explanation:

Increasing pressure favors the side that occupies less volume.
Less volume means fewer moles of gas on that side.
So equilibrium shifts toward the side with fewer gaseous moles.

Explanation:

The stoichiometric ratio is 1 A : 1 B2.
Compare amounts directly: A = 300, B2 = 400 (B2 is in excess).
Since A is fewer than B2, A will be consumed first (limiting).

Explanation:

Higher temperature increases kinetic energy of molecules.
Molecules collide more frequently and with greater energy.
So more collisions become effective (more particles cross activation energy).

Explanation:

Use Born–Haber:
ΔHf = ΔHsubl + IE + (1/2)DE(Cl2) + EA + Lattice energy.
−411 = 108 + 496 + 60.5 − 349 + U.
−411 = 315.5 + U
so U = −726.5
≈ −727 kJ/mol.

Explanation:

In benzene, the six π electrons are spread over all six carbon atoms.
This forms a continuous π cloud above and below the ring, not fixed between two carbons.
Such spreading makes the π molecular orbitals delocalized and gives extra stability.

Explanation:

In propagation, radicals react with stable molecules to form new radicals.
Cl• abstracts H from CH₄ to form HCl and CH₃• (this is the “attack” step).
Then CH₃• reacts with Cl₂ to form CH₃Cl and regenerate Cl•.

Explanation:

Carboxypeptidase is a pancreatic exopeptidase.
It removes amino acids one-by-one from the carboxyl (C-terminal) end of a polypeptide.
So deficiency reduces cleavage at the carboxyl end during protein digestion.

Explanation:

Temporary dipoles arise due to momentary electron fluctuations in atoms/molecules.
These induce dipoles in neighboring particles and create attraction.
This is called London dispersion force, present in all molecules, especially nonpolar ones.

Explanation:

A very large Kc means products are strongly favored at equilibrium.
So reactants are almost completely converted into products.
When Kc ≈ 1, both reactants and products are present in comparable amounts.

Explanation:

Ethene has a C=C double bond containing one σ and one π bond.
The π bond is weaker and more exposed, so it breaks easily in addition reactions.
Bromine adds across the double bond, causing bromine water to lose its color quickly.

Explanation:

Benzene reacts by substitution to retain aromatic stability.
An electrophile replaces a hydrogen atom on the ring.
Aromaticity is temporarily lost in the intermediate but restored after H⁺ is removed.

Explanation:

As temperature decreases, molecular kinetic energy falls sharply.
At very low temperatures, intermolecular attractions dominate and gases liquefy/solidify.
So a gas cannot remain a gas down to absolute zero in real conditions.

Explanation:

Orbital energy in multi-electron atoms depends on the sum (n + l).
Lower (n + l) means lower energy; if equal, lower n has lower energy.
Hund’s rule and Pauli principle describe electron filling and spin, not orbital energy order.

Explanation:

For AB ⇌ A⁺ + B⁻
if solubility = s
then [A⁺] = s
and
[B⁻] = s.
So Ksp = s².
s = √(9 × 10⁻⁶)
s = 3 × 10⁻³.

Explanation:

Water has maximum density at 4°C.
On freezing to ice at 0°C, hydrogen bonding forms an open lattice structure.
This structure occupies more space, so volume increases by about 9%.

Explanation:

Exothermic reactions release energy, so products end up at a lower energy level.
The difference between reactant and product energy is released as heat.
Therefore, reactants have higher energy than products.

Explanation:

In an electrolytic cell, the anode is connected to the positive terminal of the power supply.
Oxidation always occurs at the anode (loss of electrons).
Cations go to cathode for reduction, while anions move toward anode for oxidation.

Explanation:

Temperature is directly related to average kinetic energy of molecules.
If kinetic energy drops, temperature must decrease, not increase.
Internal energy increase can raise temperature, cause phase change, or help reactions by overcoming bond energies.

Explanation:

sp² hybridization produces three equivalent orbitals arranged in one plane.
They make 120° angles giving trigonal planar geometry.
In ethene, each carbon forms three σ bonds using these coplanar sp² orbitals.

Explanation:

Beryllium forms a thin, compact BeO layer on its surface when exposed to oxygen.
This oxide layer is adherent and prevents oxygen from reaching the metal beneath.
So Be shows passivation and resists further oxidation under normal conditions.

Explanation:

The gas constant R depends on the units used for pressure and volume.
For P in atm and V in dm³ (L)
the standard value is
R = 0.0821 atm·dm³·mol⁻¹·K⁻¹.
8.314 is the value when using SI units (Pa and m³) or J·mol⁻¹·K⁻¹.

Explanation:

Reaction rate depends on effective collisions between reacting particles.
Higher reactant concentration generally increases collision frequency, raising rate.
Product concentration does not directly increase forward rate in basic rate-law context.

Explanation:

Planck’s equation is E = hν.
If frequency ν doubles, photon energy E doubles proportionally.
h (Planck’s constant) is a universal constant, so it does not change.

Explanation:

k is constant for a given reaction at a fixed temperature.
Changing reactant concentration changes the rate, but not the value of k.
k mainly depends on temperature, catalyst, and nature of reactants.

Explanation:

Alpha helix is a type of secondary structure in proteins.
It is stabilized mainly by hydrogen bonds between peptide backbone groups.
Heating breaks these weak interactions, so secondary structure gets disrupted.

Explanation:

According to kinetic theory, gas pressure is produced due to collisions of gas molecules with container walls.
Molecules move randomly, are far apart, and their collisions are elastic.
So saying they “do not exert pressure” during wall collisions contradicts the theory.

Explanation:

Hydrogen spectrum is grouped into named series based on final energy level n.
The main series are Lyman, Balmer, Paschen, Brackett, and Pfund.
So the number of hydrogen spectral series commonly listed is five.

Explanation:

Electronegativity is the tendency to attract shared electrons in a bond.
Fluorine is the smallest halogen with very high effective nuclear charge.
So it attracts bonding electrons most strongly and has the highest electronegativity.

Explanation:

Positive ΔH means the forward reaction is endothermic (absorbs heat).
Lowering temperature favors the exothermic direction to release heat.
So equilibrium shifts toward reactants, meaning reverse direction is favored.

Explanation:

Acid-catalyzed hydration of alkenes follows Markovnikov’s rule.
In propene, H adds to the carbon with more hydrogens, and OH goes to the more substituted carbon.
So the major product is propan-2-ol (isopropyl alcohol).

Explanation:

In CH₃⁺ (methyl carbocation), carbon forms three σ bonds and has no lone pair.
It needs three hybrid orbitals arranged trigonal planar, so it is sp² hybridized.
PH₃, NH₃, and SbH₃ have one lone pair on the central atom and are mainly sp³.

Explanation:

Phenol is an aromatic compound all ring carbons are part of a benzene ring.
Each benzene carbon is sp² hybridized to maintain planar structure and π conjugation.
So the carbon bonded to –OH is also sp².

Explanation:

BF₃ has three bonding pairs and no lone pair on boron.
It adopts trigonal planar geometry with sp² hybridization and 120° angles.
NH₃ is pyramidal, H₂O is bent, and CH₄ is tetrahedral.

Explanation:

Bond energy increases when bond length decreases and bond becomes stronger.
Fluorine is very small, so the H–F bond is shortest among HX.
Therefore H–F has the highest bond dissociation energy.

Explanation:

Atomic number 24 is chromium (Cr).
Cr shows an exception
one electron shifts from 4s to 3d to get a half-filled d-subshell.
So its stable configuration becomes [Ar]4s¹3d⁵.

Explanation:

Cu is oxidized from 0 to +2 (loses 2 electrons).
S in H₂SO₄ is reduced from +6 to +4 in SO₂ (gains 2 electrons).
Matching electron change gives 1 Cu :
1 SO₂, then balancing H and O requires 2H₂SO₄ and 2H₂O.

Explanation:

Phenylhydrazine forms hydrazones with aldehydes and ketones (carbonyl compounds).
Butanal is an aldehyde, so it readily gives a crystalline phenylhydrazone derivative.
Butadiene, ethyl acetate, and ethanol do not form hydrazones like aldehydes/ketones.

Explanation:

4 g H₂ = 4/2 = 2 moles H₂.
Reaction:
2H₂ + O₂ → 2H₂O
so 2 moles H₂ need only 1 mole O₂.
Given O₂ is 2 moles
so O₂ is in excess.

Explanation:

Balanced reaction:
2Mg + O₂ → 2MgO
so 1 mole Mg gives 1 mole MgO.
10 moles Mg produce 10 moles MgO (oxygen is excess).
Molar mass of MgO = 24 + 16
= 40 g/mol
so mass = 10 × 40
= 400 g.

Explanation:

Alcohol adds to aldehyde under acid catalysis to form a hemiacetal first.
Hemiacetal has one –OR and one –OH on the same carbon.
With excess alcohol and acid, it can further convert into acetal.

Explanation:

Wavelength is given by
λ = v / f.
If frequency stays constant, wavelength changes directly with velocity.
When velocity doubles, λ also doubles (from 3 m to 6 m here).

Explanation:

At mean position, speed is maximum, so kinetic energy is maximum.
As the particle moves toward extreme position, speed decreases.
At extreme position, speed becomes zero, so kinetic energy becomes zero.

Explanation:

Heat flows naturally from higher temperature body to lower temperature body.
This continues until both reach the same temperature (thermal equilibrium).
It follows the second law of thermodynamics for spontaneous processes.

Explanation:

Molar specific heat means heat required per mole per 1 K rise in temperature.
So unit must include “per mole” and “per kelvin”.
That gives J mol⁻¹ K⁻¹.

Explanation:

Initial momentum = m₁v₁ = 0.02 × 300 = 6 kg·m/s
After embedding, total mass = 2 + 0.02 = 2.02 kg
Final velocity = Total momentum / Total mass
= 6 / 2.02
v ≈ 2.97 m/s
≈ 3 m/s