I85PREP
⌘ K
GPAT study materials
GPAT study resources

GPAT practice questions

One question at a time. Build your GPAT understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Pharmaceutics

According to the Biopharmaceutics Classification System, a drug is placed in Class II when it shows which combination of properties?

  1. High aqueous solubility and high intestinal permeability
  2. Low aqueous solubility and high intestinal permeability Correct answer.
  3. High aqueous solubility and low intestinal permeability
  4. Low aqueous solubility and low intestinal permeability

Explanation

The BCS classifies drugs on dose solubility and intestinal permeability. Class II covers low solubility combined with high permeability, so dissolution rate is the rate-limiting step for absorption. Class I is high/high, Class III low permeability with high solubility, and Class IV low in both.

Question 2Pharmaceutics

A tablet is compressed using a formulation in which the drug has poor wettability and low aqueous solubility. Which excipient primarily improves dissolution by reducing interfacial tension and aiding liquid penetration into the pores?

  1. A surfactant such as sodium lauryl sulfate Correct answer.
  2. A superdisintegrant such as croscarmellose sodium
  3. A glidant such as colloidal silicon dioxide
  4. An enteric polymer such as cellulose acetate phthalate

Explanation

Surfactants lower interfacial tension between the dissolution medium and the hydrophobic drug or granule surface, improving wetting and liquid penetration. Disintegrants act by swelling or wicking, glidants improve powder flow, and enteric polymers delay release rather than enhance wetting.

Question 3Pharmaceutics

In a rotary tablet press, the force that ejects the tablet from the die after compression is mainly opposed by which phenomenon?

  1. Segregation of fines in the hopper
  2. Elastic recovery of the upper punch
  3. Die-wall friction between the compact and the die surface Correct answer.
  4. Capillary rise of the granulating fluid

Explanation

During ejection the compact must slide against the die wall, and friction at this interface resists removal. Adding a lubricant such as magnesium stearate reduces die-wall friction and lowers ejection force. Elastic recovery affects capping and lamination but is not the main resistance to ejection.

Question 4Pharmaceutics

Which statement correctly describes the mechanism of a superdisintegrant such as sodium starch glycolate in a tablet?

  1. It forms an insoluble film that controls drug diffusion
  2. It swells rapidly on contact with water and disrupts the tablet matrix Correct answer.
  3. It melts at body temperature and forms a dissolving channel
  4. It neutralizes gastric acid and raises local pH

Explanation

Superdisintegrants act largely by rapid swelling and wicking when they contact aqueous fluid, generating internal pressure that breaks the compact apart. Sodium starch glycolate swells markedly, producing fast disintegration at low use levels. Film formation and acid neutralization are unrelated functions.

Question 5Pharmaceutics

A suspension for oral use shows caking that cannot be redispersed on shaking. Which formulation change is most appropriate to prevent this irreversible caking?

  1. Increase the dispersed-phase particle size by coarse milling
  2. Increase the density difference between particles and vehicle
  3. Reduce the concentration of the suspending agent to zero
  4. Add a structuring agent to produce controlled flocculation Correct answer.

Explanation

Controlled flocculation produces loose aggregates held by weak van der Waals attraction, so sediment forms a porous, easily redispersible floc instead of a hard cake. Deflocculated systems settle slowly but ultimately form compact cakes that resist shaking. Coarse particles and larger density differences worsen sedimentation.

Question 6Pharmaceutics

Which rheological behaviour is described by a system whose apparent viscosity decreases with increasing shear rate and recovers when the shear is removed, with the up and down curves forming a hysteresis loop?

  1. Newtonian flow
  2. Plastic flow with a yield value
  3. Dilatant flow
  4. Thixotropy Correct answer.

Explanation

Thixotropy is time-dependent shear thinning in which structural linkages break under shear and rebuild on standing, producing a hysteresis loop between the up and down rheograms. Newtonian flow has constant viscosity, dilatant flow thickens under shear, and plastic flow requires a yield stress but is not necessarily time dependent.

Question 7Pharmaceutics

In a two-component eutectic mixture, what is the characteristic feature of the phase diagram at the eutectic point?

  1. The components remain completely immiscible in the molten state
  2. Both components melt at the same temperature as the pure higher-melting component
  3. The two components form a solid compound with a congruent melting point
  4. The mixture melts at a single temperature lower than the melting point of either pure component Correct answer.

Explanation

At the eutectic point the liquid phase is in equilibrium with both solid components simultaneously, and this temperature is lower than the melting point of either pure substance. This is why eutectic mixtures of drugs and excipients can show depressed melting and altered physical stability.

Question 8Pharmaceutics

Which method is used to determine the particle size distribution of a dry powder in the sub-micron to micron range based on the angular scattering of a laser beam?

  1. X-ray powder diffraction
  2. Differential scanning calorimetry
  3. Laser diffraction particle size analysis Correct answer.
  4. Karl Fischer titration

Explanation

Laser diffraction measures the angular intensity of light scattered by particles; small particles scatter at wide angles and large particles at narrow angles, giving a volume-based size distribution. Karl Fischer measures water content, XRPD assesses crystallinity, and DSC measures thermal transitions.

Question 9Pharmaceutics

A powder blend is being filled into hard gelatin capsules on an automatic dosator machine. Which excipient property most directly governs the uniformity of fill weight?

  1. Good flow and consistent bulk density Correct answer.
  2. Presence of a bitter taste
  3. Colour of the powder blend
  4. High moisture content above 5 percent

Explanation

Uniform fill weight on capsule-filling machines depends on reproducible powder flow and consistent bulk density so each dosator or tamping station delivers the same mass. Poor flow causes variable fill and weight variation. Colour and taste do not affect fill weight, and excessive moisture impairs flow and stability.

Question 10Pharmaceutics

Which of the following is the principal advantage of a soft gelatin capsule over a compressed tablet for a liquid or semisolid drug formulation?

  1. It allows higher compression forces to be applied
  2. It requires no shell material and is therefore cheaper
  3. It permits incorporation of an oily vehicle as a single sealed unit dose Correct answer.
  4. It provides a tablet matrix for sustained release by compaction

Explanation

Soft gelatin capsules are formed, filled and sealed in one operation and can enclose liquids, oils and semisolids, giving a sealed unit dose suitable for water-insoluble drugs. They are not compressed, and the shell is an essential component, so the other options misdescribe the dosage form.

Question 11Pharmaceutics

A drug has a hepatic extraction ratio of 0.9 and is given orally. What is the most likely consequence for its oral bioavailability?

  1. Oral bioavailability is low because of extensive first-pass hepatic metabolism Correct answer.
  2. Oral bioavailability approaches 90 percent because absorption is complete
  3. Oral bioavailability is unaffected by hepatic blood flow
  4. Oral bioavailability equals the fraction excreted unchanged in urine

Explanation

For a drug with a high extraction ratio, most of the absorbed dose is removed during the first pass through the liver, so systemic bioavailability after oral dosing is low. Bioavailability equals the fraction escaping gut and hepatic extraction, not the absorbed fraction alone.

Question 12Pharmaceutics

According to the Noyes-Whitney equation, which change would increase the dissolution rate of a poorly soluble drug?

  1. Reducing the surface area available to the medium
  2. Increasing the surface area and reducing the diffusion layer thickness Correct answer.
  3. Lowering the solubility of the drug in the medium
  4. Increasing the particle size of the drug

Explanation

The Noyes-Whitney equation shows dissolution rate proportional to surface area and to the concentration gradient, and inversely related to diffusion layer thickness. Micronisation increases surface area and stirring reduces the boundary layer, both raising dissolution rate. Larger particles and lower solubility reduce it.

Question 13Pharmaceutics

Which type of controlled-release system delivers drug at a rate governed mainly by diffusion through a rate-controlling membrane surrounding a drug reservoir?

  1. Monolithic matrix tablet
  2. Reservoir membrane-controlled system Correct answer.
  3. Immediate-release sugar-coated tablet
  4. Osmotic pump with a laser-drilled orifice

Explanation

In a reservoir system a drug core is surrounded by a rate-controlling polymer membrane, and release is determined by diffusion across that membrane, giving near zero-order kinetics while the reservoir remains saturated. Matrix systems follow diffusion-controlled square-root kinetics, and osmotic pumps release by osmotic water influx.

Question 14Pharmaceutics

A transdermal patch is designed with a backing film, a drug reservoir, a rate-controlling membrane and an adhesive layer. Which component prevents drug loss to the environment and provides unidirectional release?

  1. The rate-controlling membrane
  2. The backing film Correct answer.
  3. The release liner that is peeled off before use
  4. The pressure-sensitive adhesive

Explanation

The backing film is an occlusive, impermeable layer that prevents drug from escaping from the patch surface and forces release towards the skin. The release liner protects the adhesive before use, the adhesive fixes the patch to skin, and the membrane controls the release rate.

Question 15Pharmaceutics

Which aerosol component is responsible for producing the fine droplet or particle cloud that reaches the lower respiratory tract from a pressurised metered-dose inhaler?

  1. The mouthpiece cap
  2. The propellant and actuator orifice together Correct answer.
  3. The canister wall thickness
  4. The drug's colour and odour

Explanation

In a pressurised metered-dose inhaler the liquefied propellant expands as it leaves the metering valve and actuator orifice, atomising the formulation into respirable droplets. Orifice diameter and propellant vapour pressure strongly influence the emitted particle size distribution.

Question 16Pharmaceutics

Which sterilisation method is appropriate for a heat-labile aqueous ophthalmic solution supplied in a sealed plastic container?

  1. Dry heat sterilisation in a hot air oven at 160 degrees Celsius
  2. Sterilisation by filtration through a 0.22 micron membrane Correct answer.
  3. Moist heat autoclaving at 121 degrees Celsius for 15 minutes
  4. Sterilisation by flaming the container

Explanation

Filtration through a 0.22 micron membrane removes bacteria without exposing the heat-labile drug to elevated temperature, and the filtered solution is then filled aseptically. Dry heat and autoclaving would degrade a heat-sensitive solute, and flaming is applicable only to metal or glass implements.

Question 17Pharmaceutics

Which test is used to confirm that a sterilising autoclave has achieved the required moist heat conditions throughout the load?

  1. Determination of the container's wall thickness
  2. Biological indicator containing Geobacillus stearothermophilus spores Correct answer.
  3. Chemical indicator that changes colour at any temperature
  4. Measurement of the solution's refractive index

Explanation

Biological indicators use highly resistant spores whose survival or destruction verifies the actual lethality delivered to the load. Geobacillus stearothermophilus spores are the standard challenge organism for moist heat sterilisation. Chemical indicators are useful adjuncts but do not prove spore kill.

Question 18Pharmaceutics

In aseptic processing, a laminar airflow hood provides protection of the product primarily by which mechanism?

  1. Sweeping airborne particles away from the critical zone with unidirectional filtered air Correct answer.
  2. Adding a chemical preservative to the air stream
  3. Creating a partial vacuum around the product
  4. Heating the air to sterilise exposed surfaces

Explanation

A laminar flow hood delivers HEPA-filtered air in a unidirectional stream that continuously sweeps particles away from the critical work area, maintaining an ISO Class 5 environment. It does not heat surfaces, add preservatives, or create a vacuum.

Question 19Pharmaceutics

Which of the following best describes the purpose of a preservative challenge test for a multi-dose ophthalmic preparation?

  1. To demonstrate that the preservative system reduces a high inoculum of specified organisms over the test period Correct answer.
  2. To determine the pH of the preparation at release
  3. To measure the viscosity of the formulation after storage
  4. To confirm that the preservative is compatible with the container closure

Explanation

The preservative efficacy test inoculates the product with specified challenge organisms and measures the decline in viable counts over time, confirming that the preservative system controls microbial growth during use. It is not a container compatibility, viscosity or pH test.

Question 20Pharmaceutics

A suppository base is required to melt at body temperature and to release a water-soluble drug readily. Which base is most suitable?

  1. Colloidal silicon dioxide
  2. White petrolatum
  3. Polyethylene glycol 4000
  4. Theobroma oil (cocoa butter) Correct answer.

Explanation

Theobroma oil melts near 34 to 36 degrees Celsius and is a suitable lipophilic base for suppositories intended to melt in the rectum. Because it is hydrophobic, it releases water-soluble drugs readily into the aqueous rectal fluid. PEG bases are water soluble, petrolatum is too occlusive and high melting, and silicon dioxide is a suspending or gelling agent.

Question 21Pharmaceutics

Which statement about the calibration curve in a UV-visible spectrophotometric assay is correct?

  1. Absorbance is directly proportional to concentration over a validated linear range Correct answer.
  2. A single-point calibration is always sufficient for a new assay
  3. Absorbance is independent of the molar absorptivity of the analyte
  4. Beer-Lambert law linearity holds only when absorbance is extremely high

Explanation

The Beer-Lambert law states that absorbance is proportional to concentration and path length for a given molar absorptivity, but linearity holds only over a validated range because stray light and molecular interactions cause deviation at high absorbance. A multi-point calibration curve is normally required to establish linearity.

Question 22Pharmaceutics

In high-performance liquid chromatography, which parameter is improved by reducing the particle size of the stationary phase in a column of the same length?

  1. The sample injection volume
  2. The detector wavelength accuracy
  3. The column efficiency and plate number Correct answer.
  4. The mobile phase pH

Explanation

Smaller stationary-phase particles shorten the diffusion path and improve mass transfer, raising the plate number and column efficiency while also increasing back pressure. This is the basis of the shift from 5 micron to sub-2 micron particles in modern HPLC.

Question 23Pharmaceutics

Which dissolution apparatus is specified for testing a transdermal patch?

  1. Apparatus 1 rotating basket
  2. Apparatus 2 paddle over disc Correct answer.
  3. Apparatus 3 reciprocating cylinder
  4. Apparatus 4 flow-through cell

Explanation

The paddle over disc apparatus (Apparatus 5 in United States Pharmacopeia nomenclature, using a paddle with a patch held on a disc at the bottom) is the standard design for transdermal patches. The rotating basket and reciprocating cylinder are intended for solid oral dosage forms, and the flow-through cell suits poorly soluble or modified-release products.

Question 24Pharmaceutics

A preformulation study shows that a drug substance is highly hygroscopic and converts to a hydrate on exposure to humidity. Which consequence is most relevant to solid dosage form development?

  1. Elimination of the need for a moisture-protective package
  2. Guaranteed improvement in aqueous solubility without any stability risk
  3. Possible changes in dissolution rate, stability and tablet hardness due to moisture uptake Correct answer.
  4. Improved flow properties with no effect on content uniformity

Explanation

Hydrate formation and moisture uptake can alter crystal form, particle size and deformation behaviour, changing dissolution, hardness and chemical stability. Such materials usually require controlled humidity during manufacture and moisture-protective packaging. Hygroscopicity rarely improves flow, and it increases rather than removes packaging needs.

Question 25Pharmaceutics

A sustained-release matrix tablet made with hydroxypropyl methylcellulose shows faster drug release than expected after three months of storage at accelerated conditions. Which explanation is most plausible?

  1. The drug crystallised into a less soluble polymorph
  2. Polymer chain entanglements increased, raising matrix viscosity
  3. Polymer degradation reduced the matrix viscosity and diffusional resistance Correct answer.
  4. The tablet gained mass through moisture uptake, reducing porosity

Explanation

If the hydrophilic matrix polymer degrades or its molecular weight falls during storage, matrix viscosity and gel strength decrease, so the diffusion barrier weakens and release accelerates. Increased entanglement, reduced porosity or a less soluble form would all slow release rather than speed it.

Question 26Pharmaceutics

Which mechanism of drug release from a hydrophilic matrix tablet is described by the Higuchi equation, where the amount released is proportional to the square root of time?

  1. Erosion-controlled release
  2. First-order dissolution from a reservoir
  3. Zero-order osmotic pumping
  4. Diffusion-controlled release from a matrix Correct answer.

Explanation

The Higuchi model describes release from a matrix in which the dissolved drug diffuses through a progressively thickening gel layer, giving cumulative release proportional to the square root of time. It is a diffusion-controlled process, not an erosion or osmotic one.

Question 27Pharmaceutics

In the classification of pharmaceutical powders by their flow behaviour, which parameter is obtained directly from the ratio of the tapped density to the bulk density of a powder?

  1. Carr's compressibility index
  2. Angle of repose
  3. Hausner ratio Correct answer.
  4. Flow rate through an orifice

Explanation

The Hausner ratio is defined as tapped density divided by bulk density and is used as an index of powder flow. Values near 1.0 indicate good flow, while higher values suggest poor flow.

Question 28Pharmaceutics

Which type of emulsion is formed when a hydrophilic surfactant with a high HLB value is used to disperse an oil phase in water?

  1. Oil-in-water emulsion Correct answer.
  2. Multiple water-in-oil-in-water emulsion
  3. Water-in-oil emulsion
  4. Anhydrous gel

Explanation

Surfactants with high HLB values are more hydrophilic and stabilise oil droplets dispersed in a continuous aqueous phase, giving an oil-in-water emulsion. Low HLB surfactants favour water-in-oil systems.

Question 29Pharmaceutics

Which excipient is added to a tablet formulation primarily to promote disintegration of the compact by drawing water into the matrix and swelling?

  1. Lactose monohydrate
  2. Magnesium stearate
  3. Microcrystalline cellulose
  4. Sodium starch glycolate Correct answer.

Explanation

Sodium starch glycolate is a superdisintegrant that swells rapidly on contact with water and breaks the tablet into granules. Disintegrants act by wicking, swelling and strain recovery.

Question 30Pharmaceutics

A drug has a pKa of 4.5 and is a weak acid. At a pH of 6.5 in the small intestine, what approximate fraction of the drug will be ionised?

  1. 50%
  2. 10%
  3. 99% Correct answer.
  4. 1%

Explanation

For a weak acid, pH minus pKa equals the log of the ratio of ionised to unionised drug. A difference of two pH units gives a ratio of 100:1, so about 99% is ionised.

Question 31Pharmaceutics

A formulation scientist wants to increase the solubility of a poorly water-soluble weak base in an aqueous vehicle. Which approach is most directly effective?

  1. Adding a co-solvent such as ethanol Correct answer.
  2. Reducing the temperature of the vehicle
  3. Adjusting the pH to below the pKa of the base
  4. Increasing the particle size of the drug

Explanation

Water-miscible co-solvents such as ethanol lower the polarity of the vehicle and increase the solubility of lipophilic drugs. This is a standard solubilisation strategy for poorly soluble compounds.

Question 32Pharmaceutics

In a stability study, a drug follows first-order degradation with a rate constant of 0.02 per month at 25 degrees Celsius. What is the approximate shelf life (t90) in months?

  1. 50.0 months
  2. 11.0 months
  3. 5.3 months Correct answer.
  4. 34.7 months

Explanation

For first-order kinetics, t90 equals 0.105 divided by the rate constant. Substituting 0.02 per month gives approximately 5.3 months, the time for 10% degradation.

Question 33Pharmaceutics

Which unit operation is used to reduce the particle size of a wet slurry of a thermolabile drug without generating excessive heat?

  1. Fluid bed drying
  2. Bead milling Correct answer.
  3. Ball milling
  4. Roller compaction

Explanation

Bead milling uses small grinding beads in a liquid vehicle and can be operated with cooling, making it suitable for thermolabile materials and for producing nanosuspensions.

Question 34Pharmaceutics

A tablet is compressed on a rotary press and shows capping at high compression force. Which formulation factor is the most likely cause?

  1. Insufficient binder concentration Correct answer.
  2. Too high a moisture content
  3. Presence of a glidant
  4. Excessive fines in the granulation

Explanation

Capping occurs when the compact lacks sufficient tensile strength, often because the binder level is too low to bond particles. Increasing binder or improving granule strength usually resolves it.

Question 35Pharmaceutics

Which statement correctly describes the role of the rate-controlling membrane in a reservoir-type transdermal patch?

  1. It provides the adhesive contact with the skin
  2. It stores the drug in a dissolved or dispersed form
  3. It prevents drug release until the patch is removed
  4. It governs the rate at which drug diffuses from the reservoir to the skin surface Correct answer.

Explanation

In a reservoir patch, the drug diffuses from the reservoir through a polymer membrane whose thickness and permeability determine the release rate. The membrane thus controls the delivery kinetics.

Question 36Pharmaceutics

A parenteral product is terminally sterilised by moist heat. Which combination of conditions is generally required to achieve a sterility assurance level of 10 to the minus 6?

  1. 121 degrees Celsius for 15 minutes Correct answer.
  2. 134 degrees Celsius for 3 minutes
  3. 100 degrees Celsius for 30 minutes
  4. 160 degrees Celsius for 2 hours

Explanation

Saturated steam at 121 degrees Celsius for 15 minutes is the classic reference cycle that provides an F0 of about 15 minutes and a sterility assurance level of 10 to the minus 6 for typical bioburdens.

Question 37Pharmaceutics

A suspension for oral use shows rapid sedimentation and the sediment is difficult to redisperse. Which formulation change is most appropriate?

  1. Increasing the particle size of the dispersed phase
  2. Reducing the viscosity of the continuous phase
  3. Decreasing the density difference between phases by using a less dense vehicle
  4. Adding a structuring agent to increase the yield value Correct answer.

Explanation

A structured vehicle with a yield value prevents settling and keeps the sediment soft and easily redispersed. Thixotropic suspending agents are commonly used for this purpose.

Question 38Pharmaceutics

In a dissolution test using USP Apparatus 2, which change would most likely increase the measured dissolution rate of a poorly soluble drug from an immediate-release tablet?

  1. Increasing the volume of dissolution medium Correct answer.
  2. Decreasing the temperature of the medium
  3. Using a medium in which the drug is less soluble
  4. Decreasing the paddle rotation speed

Explanation

Increasing the volume of dissolution medium increases the concentration gradient and the sink condition, which raises the dissolution rate. Sink conditions are important for poorly soluble drugs.

Question 39Pharmaceutics

A drug is formulated as a solid dispersion with a hydrophilic polymer to improve oral bioavailability. Which mechanism best explains the improvement?

  1. Increased hepatic clearance of the drug
  2. Reduction of the drug's first-pass metabolism
  3. Increased dissolution rate and apparent solubility of the drug Correct answer.
  4. Formation of a covalent bond between drug and polymer

Explanation

In a solid dispersion, the drug is molecularly dispersed or finely divided in a hydrophilic carrier, which increases its surface area and apparent solubility and thus its dissolution rate. Faster dissolution in the gut can improve absorption of poorly soluble drugs.

Question 40Pharmaceutics

A sustained-release matrix tablet made with hydroxypropyl methylcellulose shows faster drug release than expected after storage at high humidity. Which explanation is most plausible?

  1. The tablet porosity decreased due to sintering
  2. The polymer underwent cross-linking and became more hydrophobic
  3. Moisture plasticised the polymer and increased its hydration and swelling rate Correct answer.
  4. The drug crystallised and became more soluble

Explanation

Water acts as a plasticiser for hydrophilic cellulose ethers, lowering the glass transition temperature and accelerating polymer hydration and gel formation. This can increase the release rate of the matrix.

Question 41Pharmaceutical Chemistry

Which physicochemical property of a drug is most directly estimated by its partition coefficient (log P) between octanol and water?

  1. Molar refractivity
  2. Lipophilicity Correct answer.
  3. Hydrogen-bond basicity
  4. Ionization constant

Explanation

The octanol-water partition coefficient expresses how a neutral solute distributes between a lipophilic and an aqueous phase, so it is the standard measure of lipophilicity. It correlates with membrane permeability and receptor binding but is not a measure of pKa, molar refractivity, or hydrogen-bond basicity.

Question 42Pharmaceutical Chemistry

In the pH-partition hypothesis, an acidic drug with pKa 4.4 placed in a compartment at pH 1.4 will exist predominantly in which form?

  1. Ionized, with about 99.9% as anion
  2. Unionized, with about 99.9% as free acid Correct answer.
  3. Equal mixtures of ionized and unionized species
  4. Unionized, with about 50% as free acid

Explanation

For a weak acid the Henderson-Hasselbalch relation gives pH − pKa = log([A−]/[HA]); here 1.4 − 4.4 = −3, so the ratio of anion to free acid is 1:1000. Thus roughly 99.9% remains unionized, which favors absorption across lipid membranes in the gastric environment.

Question 43Pharmaceutical Chemistry

Which statement correctly describes the role of the pro-R hydrogen in the stereochemical course of an enzyme-catalyzed reduction of a ketone?

  1. It is abstracted as a proton from the re face
  2. It is transferred as a hydrogen atom to the si face
  3. It is removed as a hydride from one specific face of the carbonyl Correct answer.
  4. It determines the absolute configuration of the alcohol product

Explanation

Dehydrogenases typically deliver or remove hydride stereospecifically from one face of the planar carbonyl group, which fixes the configuration of the new stereocenter. The pro-R hydrogen label identifies which of two chemically equivalent hydrogens is removed, but the transfer itself is hydride, not a free proton or hydrogen atom.

Question 44Pharmaceutical Chemistry

Which functional group is responsible for the characteristic strong carbonyl stretching band near 1700 cm⁻¹ in an IR spectrum?

  1. Nitrile
  2. Carbonyl Correct answer.
  3. Hydroxyl
  4. Amine

Explanation

Carbonyl groups absorb strongly in the 1650–1750 cm⁻¹ region because the C=O stretch produces a large change in dipole moment. Hydroxyl, nitrile, and amine groups give bands at distinctly different frequencies.

Question 45Pharmaceutical Chemistry

A proton in a ¹H NMR spectrum appears as a triplet. Which neighboring environment is consistent with this multiplicity?

  1. Two equivalent neighboring protons Correct answer.
  2. One neighboring proton
  3. Three equivalent neighboring protons
  4. Zero neighboring protons

Explanation

According to the n+1 rule, a signal split into a triplet indicates two equivalent protons on adjacent atoms. The relative intensities follow the binomial pattern 1:2:1 for a triplet.

Question 46Pharmaceutical Chemistry

In mass spectrometry, which ionization technique is best suited to a thermally labile, high-molecular-weight peptide?

  1. Thermal desorption
  2. Electrospray ionization Correct answer.
  3. Chemical ionization
  4. Electron ionization

Explanation

Electrospray ionization transfers large, fragile biomolecules from solution into the gas phase as multiply charged ions without significant fragmentation. It is therefore preferred for peptides and proteins that would decompose under harsh ionization.

Question 47Pharmaceutical Chemistry

Which detector is most commonly paired with a UV–visible spectrophotometer for routine quantitative analysis in a pharmaceutical QC laboratory?

  1. Photomultiplier tube Correct answer.
  2. Flame ionization detector
  3. Thermal conductivity cell
  4. Electron capture detector

Explanation

Photomultiplier tubes convert the transmitted light into an amplified electrical signal and are the standard UV–visible detectors. The other listed detectors belong to chromatographic systems rather than to spectrophotometry.

Question 48Pharmaceutical Chemistry

Which chromatographic parameter is defined as the time elapsed between injection and the appearance of the peak maximum for an analyte?

  1. Retention time Correct answer.
  2. Resolution
  3. Capacity factor
  4. Selectivity factor

Explanation

Retention time is the interval from injection to the peak maximum and is the fundamental qualitative descriptor in chromatography. Capacity factor, selectivity, and resolution are derived quantities describing retention relative to the void volume and separation quality.

Question 49Pharmaceutical Chemistry

In reversed-phase HPLC, which change will most reliably increase the retention of a moderately polar neutral analyte?

  1. Decreasing the injection volume
  2. Increasing the organic modifier content
  3. Increasing the water content of the mobile phase Correct answer.
  4. Raising the column temperature

Explanation

Reversed-phase retention increases as the mobile phase becomes more aqueous, because the analyte partitions more strongly into the nonpolar stationary phase. Adding organic modifier, raising temperature, or changing injection volume does not increase retention in this way.

Question 50Pharmaceutical Chemistry

Which titration is appropriate for assaying a weakly basic drug that is insoluble in water but soluble in glacial acetic acid?

  1. Complexometric titration with EDTA
  2. Redox titration with ceric sulfate
  3. Aqueous acid–base titration with NaOH
  4. Non-aqueous titration with perchloric acid Correct answer.

Explanation

Weak bases are titrated as their acetate salts in glacial acetic acid using perchloric acid, an approach that sharpens the endpoint in a differentiating solvent. Aqueous alkali, redox, and complexometric methods do not suit this weakly basic, water-insoluble analyte.