- Pharmaceutical analysis primarily involves:
a) Designing drug delivery systems
b) Detection, identification and quantification of compounds
c) Performing clinical trials
d) Manufacturing processes
Answer: b - Which technique is mainly qualitative?
a) Volumetric titration
b) Gravimetry
c) Spot tests and colour tests
d) Potentiometry
Answer: c - Which technique is mainly quantitative?
a) Thin layer chromatography (TLC) for identity only
b) Spectrophotometry for concentration measurement
c) Spot test for presence/absence
d) Odour test
Answer: b - The expression “% w/v” means:
a) g solute per 100 mL solution
b) g solute per 100 g solvent
c) mg solute per L solution
d) mol solute per L
Answer: a - Molarity (M) is defined as:
a) moles solute per kg solvent
b) equivalents per liter
c) moles solute per liter solution
d) grams solute per 100 mL solution
Answer: c - Molality (m) is defined as:
a) moles solute per liter of solution
b) moles solute per kg of solvent
c) equivalents per liter
d) grams per 100 mL
Answer: b - Normality (N) is:
a) moles/L
b) equivalents/L
c) g/L
d) mol/kg
Answer: b - ppm stands for:
a) percent per milliliter
b) parts per million
c) probability per mole
d) parts per microgram
Answer: b - A good primary standard should be:
a) hygroscopic and impure
b) cheap and volatile
c) stable, pure and non-hygroscopic
d) colored and reactive with air
Answer: c - Which of the following is a commonly used primary standard in acid–base titrimetry?
a) Sodium hydroxide (NaOH)
b) Oxalic acid (H2C2O4) or potassium hydrogen phthalate (KHP)
c) Hydrochloric acid (HCl)
d) Sulfuric acid (H2SO4)
Answer: b - A secondary standard is:
a) Always more pure than a primary standard
b) Standardized against a primary standard
c) Unstable and never used
d) A mixture of two standards
Answer: b - To prepare 1.0 L of 1.0 M NaOH (approx.), the mass of solid NaOH required is about:
a) 11 g
b) 23 g
c) 40 g
d) 58 g
Answer: c - Sodium thiosulphate (Na2S2O3) solutions are commonly standardized against:
a) Standard iodine solution (I2)
b) KMnO4 directly
c) HCl
d) NaOH
Answer: a - Potassium permanganate (KMnO4) is usually standardized against:
a) Oxalic acid in acidic medium
b) NaOH solution
c) Na2S2O3
d) Silver nitrate
Answer: a - Ceric ammonium sulphate (Ce(IV)) is standardized against:
a) Ferrous ammonium sulphate (Mohr’s salt)
b) Silver nitrate
c) Sodium carbonate
d) Potassium dichromate
Answer: a - HCl standard solutions can be prepared and standardized using:
a) Primary standard Na2CO3 (sodium carbonate)
b) NaOH without standardization
c) KMnO4
d) Na2S2O3
Answer: a - Sulfuric acid (H2SO4) primary-standard preparation requires care because:
a) It is volatile
b) It is a non-oxidizing acid
c) It is hygroscopic and exothermic on dilution
d) It is colorless
Answer: c - The main source of systematic error is:
a) Random fluctuations in readings
b) Personal mistakes only
c) Instrumental bias or calibration error
d) Atmospheric pressure only
Answer: c - Random errors can be minimized by:
a) Calibration of instruments only
b) Repeating measurements and statistical treatment
c) Throwing away bad data without record
d) Using uncalibrated equipment
Answer: b - A “blank determination” helps to:
a) Increase concentration
b) Eliminate systematic errors from reagents and glassware
c) Reduce random error only
d) Provide the final result directly
Answer: b - Accuracy refers to:
a) Reproducibility of results
b) Closeness of measured value to true value
c) Number of significant figures only
d) Speed of analysis
Answer: b - Precision is:
a) Closeness of repeated measurements to each other
b) Closeness to true value
c) The same as accuracy
d) Number of decimal places
Answer: a - Significant figures in a measurement convey:
a) Random error size
b) Certainty and precision of the measurement
c) Purity of reagent
d) Colour change point
Answer: b - Pharmacopoeia provides:
a) Recipes for medicines only
b) Official standards for identity, purity and assay of drugs
c) Clinical guidelines for physicians
d) Marketing strategies for pharmaceuticals
Answer: b - Limit tests in pharmacopoeial analysis are primarily:
a) Qualitative comparative tests for specified impurities
b) Quantitative assays for active ingredients
c) Physical tests for tablet hardness
d) Perfume tests for formulations
Answer: a - Typical techniques listed under “different techniques of analysis” include:
a) Titrimetry, gravimetry, spectrophotometry, chromatography, electrochemical methods
b) Only titration
c) Only chromatography
d) Microbiological tests only
Answer: a - To prepare a 0.1 N solution of H2SO4 (considering equivalents), you need to know:
a) Only density of acid
b) Equivalent weight of H2SO4 and desired volume
c) Colour of acid
d) Melting point of acid
Answer: b - Which reagent is frequently used as a drying agent during primary standard handling?
a) Water
b) Silica gel or desiccator (e.g., phosphorus pentoxide or calcium chloride)
c) Ethanol
d) NaOH solution
Answer: b - The purpose of standardizing volumetric solutions is to:
a) Change the solute identity
b) Determine the exact concentration for accurate titrations
c) Make them colored
d) Increase pH only
Answer: b - Which of the following is NOT a desirable property of a primary standard?
a) High purity
b) High molecular weight
c) Hygroscopic
d) Stable on storage
Answer: c - Preparation of a molar solution involves:
a) Dissolving the substance in a liter of solvent irrespective of weight
b) Calculating the mass from molar mass and desired molarity then making up to volume
c) Just weighing approximate amount
d) Heating the solvent to boiling
Answer: b - In volumetric analysis, the burette reading should be read:
a) From the top of the meniscus
b) At eye level at the bottom of the meniscus
c) At an angle to avoid parallax
d) Without looking at it
Answer: b - Which compound is commonly used to standardize sodium hydroxide besides oxalic acid?
a) Potassium hydrogen phthalate (KHP)
b) Potassium permanganate
c) Silver nitrate
d) Barium chloride
Answer: a - Which solution is commonly used to standardize sodium thiosulphate?
a) Standard iodine solution (prepared from KIO3 + KI)
b) NaOH solution
c) HCl solution
d) KMnO4 solution
Answer: a - For standardization of KMnO4 by oxalic acid, the medium should be:
a) Strongly basic
b) Neutral
c) Strongly acidic (sulphuric acid) and heated
d) Organic solvent only
Answer: c - When performing a titration, an “indicator” is used to:
a) Change the concentration of analyte
b) Provide a sharp physical change at or close to equivalence point
c) Destroy interfering ions
d) Increase the titrant strength
Answer: b - Which of the following is an example of a technique to minimize error?
a) Never replicate measurements
b) Use calibrated instruments and perform replicate analyses
c) Ignore temperature effects
d) Use expired reagents
Answer: b - Stability on storage is required for a primary standard to ensure:
a) It changes colour over time
b) Its composition and weight remain constant
c) It melts easily
d) It dissolves slowly
Answer: b - A volumetric flask used to prepare standard solutions is calibrated at:
a) Room temperature only
b) Boiling point of water
c) A specified temperature (usually 20–25 °C) for volume accuracy
d) Any temperature randomly
Answer: c - Which of these is a correct step in standardizing a solution?
a) Preparing approximate concentration only and never adjusting
b) Titrating against a primary standard and calculating exact concentration
c) Ignoring purity of primary standard
d) Diluting without mixing
Answer: b - pH at the equivalence point of a strong acid vs strong base titration is:
a) < 7
b) = 7 (approx.)
c) > 7
d) Variable without relation
Answer: b - pH at the equivalence point of a weak acid titrated with a strong base is:
a) < 7
b) = 7
c) > 7
d) Always 14
Answer: c - pH at the equivalence point of a weak base titrated with a strong acid is:
a) < 7
b) = 7
c) > 7
d) 0
Answer: a - Which of the following indicators is suitable for strong acid vs strong base titration?
a) Methyl orange (pH range ~3.1–4.4)
b) Phenolphthalein (pH range ~8.2–10)
c) Bromothymol blue (pH range ~6.0–7.6)
d) Any of the above depending on equivalence pH; bromothymol blue often used for strong/strong
Answer: d - The theory used to explain colour change of acid–base indicators is based on:
a) Kinetic theory of gases
b) Indicator acid–base equilibrium and pKa relative to pH (Henderson–Hasselbalch concept)
c) Thermodynamics only
d) Only solubility differences
Answer: b - An indicator should have a transition range that:
a) Lies far from the equivalence pH
b) Encompasses the equivalence pH for the titration in question
c) Is always below pH 3
d) Is always above pH 10
Answer: b - Neutralization curve shows:
a) Temperature vs time
b) pH vs volume of titrant added
c) Concentration vs molarity
d) Mass vs volume
Answer: b - Titration of a very weak acid with a strong base yields an equivalence point:
a) At pH 7
b) At pH > 7 but with a small pH jump
c) At pH < 3 only
d) No titration possible
Answer: b - Non-aqueous titration is especially useful for:
a) Very water-soluble strong acids only
b) Organic substances insoluble or unstable in water (weak acids/bases)
c) Only for metals
d) None of the above
Answer: b - Common solvents for non-aqueous titration include:
a) Glacial acetic acid and anhydrous ethanol/dioxane mixtures
b) Pure water only
c) Liquid ammonia only
d) Benzene only
Answer: a - In non-aqueous acidimetry, glacial acetic acid (GAA) acts as:
a) A base only
b) Solvent and weakly acidic medium in which bases behave stronger
c) An inert gas
d) An oxidizing agent
Answer: b - Ephedrine HCl (a basic drug) is commonly estimated by:
a) Aqueous acid–base titration only
b) Non-aqueous titration (acidimetry) if necessary for improved endpoint and solubility
c) Gravimetry only
d) Colorimetry only
Answer: b - Sodium benzoate (a weak acid salt) can be estimated by:
a) Aqueous neutral titration only
b) Non-aqueous acidimetry or alkalimetry if appropriate solvent chosen
c) Polarography only
d) Conductometry only
Answer: b - The endpoint detection in non-aqueous titration may use indicators whose pKa in non-aqueous solvent is appropriate; this differs from aqueous indicators because:
a) Indicator pKa shifts with solvent properties
b) Non-aqueous solutions have same pKa always
c) Color change is instant in water but not in GAA
d) Indicators don’t work in non-aqueous media
Answer: a - The titration curve of strong acid vs weak base shows:
a) Large pH jump at equivalence
b) Small pH change with no jump
c) No equivalence point
d) Identical to weak acid vs strong base
Answer: a - Choice of indicator for titration of weak acid vs weak base is:
a) Easy because pH jump is large
b) Difficult because equivalence pH change is small — instrumental detection preferred
c) Not necessary
d) Always methyl orange
Answer: b - The equivalence point of a titration is:
a) Always identical to the endpoint observed by an indicator
b) The theoretical point where stoichiometric amounts are reacted; endpoint is practical indicator signal close to equivalence
c) The point at which titrant bottle is empty
d) The colour of the solution
Answer: b - Which instrument gives precise titration endpoints for weak acid–weak base titrations?
a) Visual indicator only
b) Potentiometer (pH meter) or conductometer
c) Balance only
d) Thermometer only
Answer: b - In acid–base titrations, temperature changes during mixing can:
a) Affect equilibrium and pH slightly and should be controlled
b) Have no effect at all
c) Be used to determine concentration directly
d) Always improve accuracy
Answer: a - When preparing molar solutions of strong acids, one should:
a) Add acid to water slowly with cooling (always add acid to water)
b) Add water to concentrated acid quickly
c) Mix equal parts without care
d) Heat acid before mixing with water
Answer: a - Methyl orange is a suitable indicator for titrations with equivalence pH near:
a) 9–11
b) 3–4.5
c) 7–8
d) 11–13
Answer: b - Phenolphthalein is colourless in:
a) Neutral and acidic media, pink in alkaline
b) Acidic and alkaline, colourless at neutral
c) Always pink
d) Always colourless
Answer: a - A titration of a polyprotic acid may show:
a) A single equivalence point only
b) Multiple equivalence points corresponding to each dissociation
c) No equivalence point at all
d) Only half-equivalence points
Answer: b - The half-equivalence point in a weak acid titration is the point where:
a) Indicator changes colour twice
b) pH = pKa of the weak acid (Henderson–Hasselbalch)
c) Titration stops permanently
d) All acid is neutralized
Answer: b - For titration of a weak acid with a weak base, the pH change at equivalence is:
a) Very large and easy to see visually
b) Small and difficult to detect visually—instrumental methods preferred
c) Always 7
d) Negative
Answer: b - Which of the following is a limitation of non-aqueous titrations?
a) Wide variety of solvent choices with no issues
b) Solvent purity and water content greatly affect results
c) They are always simpler than aqueous titrations
d) Indicators behave exactly as in water
Answer: b - In titrations where water reacts with analyte, non-aqueous titration is useful because:
a) It increases water content deliberately
b) It prevents hydrolysis by using aprotic or weakly protic solvents
c) It always reduces solubility
d) It removes the need for indicators
Answer: b - Typical endpoint detection in non-aqueous titration may rely on:
a) Visual indicators with shifted colour ranges or potentiometric detection
b) Only conductivity measurements
c) Only gravimetric measurement
d) Smell of solution
Answer: a - When titrating a weak base with perchloric acid in glacial acetic acid, the endpoint indicator should:
a) Have pKa appropriate in GAA medium
b) Be the same indicator as in water always
c) Be a redox indicator
d) Be starch only
Answer: a - The theory of indicators accounts for which phenomena?
a) Colour difference between protonated and deprotonated forms of indicator molecule and their pKa/pH relation
b) Colour of solvent only
c) Evaporation rate of solvent
d) Viscosity of solution
Answer: a - In aqueous titrations, the titration curve steepness depends on:
a) Ionic strength only
b) Concentration of analyte and relative strengths of acid/base — steep for strong/strong
c) Colour of solution
d) pH meter brand
Answer: b - A visual indicator shows a sudden colour change at the endpoint because:
a) It is destroyed by titrant
b) The indicator’s equilibrium shifts rapidly across its colour transition near equivalence pH
c) It precipitates out of solution
d) The indicator is consumed by analyte
Answer: b - Which factor is critical in selecting an indicator?
a) Price only
b) Transition pH range matching equivalence pH of the titration
c) Smell of indicator
d) Colour matching the titrant bottle
Answer: b - A pH meter is calibrated before titrations using:
a) Random solutions
b) Standard buffer solutions at known pH values (e.g., pH 4.00, 7.00, 10.00)
c) Distilled water only
d) Primary standards only
Answer: b - Why are indicators less reliable at very low analyte concentration?
a) Colour change is permanent
b) Endpoint colour change may be faint or masked and stoichiometric volumes tiny — instrumental methods better
c) They produce bubbles
d) They evaporate
Answer: b - Non-aqueous alkalimetry usually titrates:
a) Acidic substances in protic solvents
b) Basic substances in aprotic solvents using strong bases as titrants
c) Metals only
d) Only water content
Answer: b - Which of the following is NOT a property of a good titration solvent for non-aqueous titration?
a) High purity with controlled water content
b) Inert to reagents (not reacting)
c) Proton donating or accepting behaviour appropriate to scale acidity/basicity
d) Strong oxidizing property
Answer: d - In preparing standard solutions for titrations, volumetric flasks should be filled to the calibration mark at:
a) Any temperature without concern
b) The calibration temperature indicated (often ~20–25 °C) for volume accuracy
c) Boiling temperature
d) Freezing temperature
Answer: b - When determining the strength of a base using oxalic acid, what stoichiometry is used for NaOH + H2C2O4?
a) 1:1 or 2:1 depending on dissociation (practical titrations treat oxalic acid as diprotic: 2 mol NaOH per mol oxalic acid)
b) 1:2 always
c) 1:3 always
d) 3:1 always
Answer: a - Which technique is preferred to detect equivalence in titrations with very small pH change?
a) Visual indicator only
b) Potentiometric (pH electrode) or conductometric endpoint detection
c) Smell of reagent
d) Weighing the solution
Answer: b - Mohr’s method for chloride estimation uses which titrant?
a) EDTA
b) Silver nitrate (AgNO3) with potassium chromate as indicator
c) Sodium thiosulphate
d) KMnO4
Answer: b - In Mohr’s method the end-point is signalled by formation of:
a) White AgCl precipitate only
b) Reddish-brown silver chromate (Ag2CrO4) when all chloride has precipitated
c) Blue complex color
d) Gas evolution
Answer: b - Fajans method uses:
a) Adsorption indicators that change colour when adsorbed onto precipitate surface
b) Back titration only
c) Volhard indicator only
d) Polarography only
Answer: a - Volhard’s method is a back titration used for:
a) Direct titration of chloride with AgNO3
b) Determination of halides by precipitating with excess Ag+ then titrating excess Ag+ with thiocyanate (SCN−)
c) Iodine titration only
d) pH measurement only
Answer: b - Modified Volhard’s method often uses which indicator for titration of excess Ag+?
a) Starch
b) Ferric ion to form red complex with thiocyanate (FeSCN2+)
c) Phenolphthalein
d) Methyl orange
Answer: b - In Fajans method, the adsorption indicator is often:
a) Fluorescein or dichlorofluorescein (for silver halides)
b) Eriochrome black T
c) Starch
d) KMnO4
Answer: a - Complexometric titrations commonly use which titrant for metal ion estimation?
a) HCl
b) EDTA (ethylenediaminetetraacetic acid)
c) AgNO3
d) KMnO4
Answer: b - Eriochrome Black T is used as an indicator for:
a) Acid–base titrations only
b) Complexometric titrations for Ca2+ and Mg2+ (forms wine-red complex with metal ions)
c) Redox titrations only
d) Precipitation titrations only
Answer: b - Masking agents in complexometry are used to:
a) Precipitate all ions simultaneously
b) Temporarily bind interfering metal ions so that the titration of the analyte metal may proceed selectively
c) Speed up the titration only
d) Change pH drastically
Answer: b - Demasking reagents are used to:
a) Hide the analyte
b) Release masked ions so they can be titrated after selective steps
c) Make the solution colourless only
d) Evaporate solvent
Answer: b - The determination of magnesium in a sample by EDTA commonly requires:
a) No buffer and any pH
b) Ammonia–ammonium chloride buffer to pH ~10 to keep Mg2+ complexation optimal
c) Strong acid medium only
d) Organic solvent only
Answer: b - Calcium gluconate is typically estimated by:
a) Gravimetry only
b) Complexometric titration with EDTA at appropriate pH (using an appropriate indicator)
c) Polarography only
d) Bomb calorimetry
Answer: b - Gravimetric analysis principle involves:
a) Measuring the weight of a precipitate after isolation and drying/ignition to constant weight
b) Measurement of color change only
c) Measurement of conductivity only
d) Titration against standard solution only
Answer: a - Co-precipitation refers to:
a) Intentional removal of analyte only
b) Incorporation of impurities in the precipitate leading to error in gravimetry
c) Post-titration heating steps
d) Evaporation of solvent
Answer: b - Post-precipitation means:
a) Additional precipitation of analyte after filtration leading to loss and error
b) Precipitate removing impurities only
c) A titration technique
d) Indicator selection method
Answer: a - Barium sulphate (BaSO4) is commonly used in gravimetric analysis because it is:
a) Highly soluble and easily washed away
b) Very insoluble and forms a stable precipitate for weighing
c) Volatile on drying
d) Colored only
Answer: b - The important step in gravimetric analysis to ensure accuracy is:
a) Not washing the precipitate at all
b) Proper precipitation, thorough washing, drying/ignition to constant weight, and avoiding losses
c) Using impure reagents
d) Rapid filtration without control
Answer: b - Diazotisation titration is based on:
a) Formation of diazonium salts from primary aromatic amines under cold acidic conditions and using this chemistry for quantitative analysis (used in some pharmaceutical titrations)
b) Precipitation only
c) Redox only
d) Conductometric detection only
Answer: a - Diazotisation can be used in analytical chemistry for:
a) Estimation of aniline derivatives after conversion to diazonium salts and coupling reactions or titrations
b) Estimation of inorganic chlorides only
c) Gravimetric estimation of sulfates only
d) None of the above
Answer: a - Which of the following is a key control to prevent co-precipitation errors?
a) Very rapid precipitation formation always
b) Controlled rate of precipitation, correct pH and adequate digestion/aging of precipitate
c) Using cold solutions only
d) Not filtering the precipitate at all
Answer: b - In complexometric titration, the end point with Eriochrome Black T for Ca/Mg is indicated by:
a) Blue to red colour change
b) Red to blue colour change (wine-red to blue when EDTA complexes metal ions)
c) Precipitate formation only
d) Gas evolution
Answer: b - Which is a typical masking agent for Fe(III) during EDTA titration?
a) Hydrogen peroxide
b) Sodium fluoride (forms stable complexes with Fe) or cyanide (dangerous) — but fluoride commonly used in controlled conditions
c) Acetic acid
d) KMnO4
Answer: b - Which parameter is crucial for Fajans method sensitivity?
a) Temperature only
b) Surface adsorption properties and the nature of the precipitate and indicator
c) Colour of solution only
d) Current of a nearby instrument
Answer: b - In Volhard’s back titration for chloride, the precipitated AgCl is removed and the excess Ag+ is titrated with:
a) Na2S2O3 directly
b) Standard thiocyanate (KSCN) in presence of Fe3+ to form red complex at endpoint
c) EDTA
d) KMnO4
Answer: b - In precipitation titrations, the solubility product (Ksp) is important to:
a) Ensure complete and quantitative precipitation of analyte
b) Avoid any calculation
c) Increase impurity incorporation only
d) Determine pH only
Answer: a - The principle of using BaSO4 for sulfate estimation relies on:
a) Highly soluble barium sulfate formation
b) Insolubility of BaSO4 so that sulfate can be precipitated and weighed as BaSO4
c) Color change only
d) Formation of gaseous product
Answer: b - For gravimetric estimation of BaSO4, HCl must be avoided because:
a) HCl reacts with barium carbonate but not with sulfate — main concern is interfering anions and correct acidity for precipitation
b) HCl dissolves BaSO4 readily
c) HCl always increases precipitation
d) HCl is never used in gravimetry
Answer: a - Which solvent condition is commonly used for EDTA titration of Ca2+?
a) Highly acidic pH 1–2
b) Buffered to pH ~10 (ammonia buffer) to promote EDTA complexation and proper indicator response
c) Strongly oxidizing medium
d) Non-aqueous acetic acid
Answer: b - Which of the following is an advantage of complexometric titration?
a) No need for pH control
b) High selectivity for metal ions and rapid endpoints with good indicators
c) Always more time-consuming than gravimetry
d) Only works for silver ions
Answer: b - In Mohr’s titration, which interfering ion must be absent?
a) Bromide and iodide can interfere; chromate indicator also affected by turbidity and pH — specifically presence of ions that form insoluble silver salts (like bromide/iodide) can complicate endpoint
b) Sulfate only
c) Nitrate only
d) None matter
Answer: a - Redox titrations are based on:
a) Proton transfer only
b) Electron transfer (oxidation–reduction) reactions occurring quantitatively between titrant and analyte
c) Adsorption only
d) No chemical change
Answer: b - Cerimetry uses Ce(IV) salts as:
a) Reducing agents
b) Oxidizing titrants (Ce(IV) oxidizes analytes; standardized against ferrous salts)
c) Indicators only
d) Precipitants only
Answer: b - In iodometry, the titrant is:
a) Standard iodine added directly to analyte always
b) Sodium thiosulphate titrates iodine produced or liberated (iodometry is often titration of liberated iodine with thiosulfate)
c) KMnO4 directly
d) EDTA
Answer: b - Iodimetric titration is commonly used for:
a) Estimation of reducing agents by titrating iodine generated from known oxidant amounts (terminology varies; iodimetric/iodometric used depending on whether iodine is titrated or produced)
b) Only acids
c) Only bases
d) Gravimetric analyses only
Answer: a - Bromatometry typically uses bromate (KBrO3) in acidic medium to generate:
a) Chlorine gas
b) Bromine in situ which oxidizes analytes and endpoint determined appropriately
c) Hydrogen gas
d) EDTA complexes
Answer: b - Dichrometry commonly uses:
a) KMnO4 only
b) Potassium dichromate (K2Cr2O7) as titrant in acid medium for reducing agents like Fe(II)
c) KBrO3 only
d) Sodium carbonate only
Answer: b - Which is a common example of an oxidimetric titration?
a) KMnO4 titration of ferrous sulphate (Fe2+)
b) EDTA titration of Ca2+
c) Gravimetric precipitation of BaSO4
d) Mohr’s chloride titration
Answer: a - A common indicator for thiosulfate titrations of iodine is:
a) Phenolphthalein
b) Starch — forms blue complex with iodine; at near endpoint starch disappears allowing sharp endpoint detection
c) Methyl orange
d) Eriochrome black T
Answer: b - In cerimetry, the Ce(IV)/Ce(III) redox pair has which characteristic that is useful?
a) Very slow kinetics only
b) Strong oxidizing power and reasonably stable in acidic solution when prepared fresh for titrations
c) No reaction with analytes
d) It is always a reducing reagent
Answer: b - Iodine is usually stored in solution as:
a) I2 in water only
b) Stabilized as I2 in KI solution (iodine–iodide solution) for standard used in titrations
c) As NaI only
d) As KCl only
Answer: b - In an iodometric determination of copper(II), Cu2+ is reduced to Cu+ by iodide with liberation of:
a) Chlorine gas
b) Iodine (I2) which is then titrated with sodium thiosulfate
c) Hydrogen gas
d) Bromine gas
Answer: b - In titrations involving KMnO4 as oxidant, the endpoint is self-indicating because:
a) Permanganate is a strong oxidant with intense purple colour and disappears on reduction; a faint pink persists at endpoint
b) It forms a gas
c) It never changes colour
d) It precipitates
Answer: a - In bromatometry, the titration reactions usually require:
a) Alkaline medium only
b) Acidic medium (often HCl/H2SO4) for generating bromine from bromate and bromide
c) Presence of EDTA only
d) Polarographic detection only
Answer: b - In dichrometry with dichromate, an internal indicator sometimes used is:
a) Diphenylamine or external indicators depending on method; dichromate titrations often use internal redox indicators or back-titration techniques
b) Eriochrome black T
c) Bromothymol blue
d) Litmus only
Answer: a - In redox titrations, equivalent weight of oxidant depends on:
a) Number of electrons transferred in the redox reaction per mole
b) Colour only
c) Viscosity only
d) pH only
Answer: a - A consequence of using improper acid in KMnO4 titration is:
a) Faster endpoint detection always
b) Slower or incomplete reaction or side reactions (correct acid like sulphuric acid is required; nitric or hydrochloric cause problems)
c) No effect at all
d) KMnO4 becomes basic
Answer: b - Which titration is commonly used for estimation of ascorbic acid?
a) EDTA titration
b) Iodimetric/iodometric titration (ascorbic acid reduces iodine; iodometric methods commonly used)
c) Gravimetric titration
d) Mohr’s method
Answer: b - For redox titrations, the standardization of titrant is essential because:
a) Titrant volume is irrelevant
b) Only standardized titrant gives accurate quantitative results — standardization often against primary standards or well-characterized secondary standards
c) Titrant is always perfect concentration as sold
d) Titrant concentration does not change with time
Answer: b - In redox titration stoichiometry, if titrant provides 2 electrons per mole and analyte 1 electron per mole, equivalent weight relationships require:
a) No balancing
b) Adjusting stoichiometry to electrons transferred (1 mol titrant oxidizes 2 mol analyte if electron numbers permit etc.)
c) Using half the normal volume always
d) Using color only
Answer: b - Which of the following would NOT be a typical redox titration application?
a) Determination of iron(II) by KMnO4
b) Determination of sulphite by iodine
c) Determination of calcium by EDTA
d) Determination of hydrogen peroxide by potassium permanganate or ceric reagents
Answer: c - Titration with potassium iodate (KIO3) is often used to generate:
a) Chlorine gas directly
b) Known amounts of iodine in acidic medium (KIO3 + KI + acid produce iodine) for subsequent titration or standardization
c) EDTA complexes only
d) Precipitates only
Answer: b - In iodometric standardization of sodium thiosulfate, the procedure typically involves standard iodine that reacts stoichiometrically with thiosulfate to:
a) Produce a precipitate
b) I2 + 2 S2O32− → 2 I− + S4O62− (thiosulfate reduces iodine); the stoichiometry used for calculation is important
c) Oxidize thiosulfate to sulphate only
d) Form EDTA complex
Answer: b - In cerimetry, standards are usually prepared fresh because Ce(IV) solutions:
a) Are highly stable indefinitely
b) Can be slowly reduced by atmospheric oxygen or impurities so fresh preparation and storage in dark is often recommended for accuracy
c) Explode if stored
d) Are gaseous at room temperature
Answer: b - For reliable redox titrations, it’s often necessary to:
a) Use impure reagents only
b) Control reaction conditions (acidic medium, temperature) to avoid side reactions and ensure fast, complete reaction
c) Never standardize reagents
d) Skip blank titrations always
Answer: b - Which technique is useful to confirm endpoint in redox titrations besides indicators?
a) Potentiometric endpoint detection (measuring potential change) or amperometric methods
b) Smell
c) Visual observation of bubbles always
d) Weight measurement only
Answer: a - In iodometric titrations, the presence of reducing impurities will:
a) Not affect the result
b) Consume iodine and give falsely high values for analyte that liberates iodine (so blank corrections or separation necessary)
c) Always be beneficial
d) Make endpoint colourless immediately
Answer: b - Which redox titrant is often used for organic oxidizable substances (e.g., some pharmaceuticals)?
a) KMnO4 in acid media or ceric ammonium sulphate depending on substrate reactivity
b) NaCl only
c) EDTA
d) AgNO3
Answer: a - A redox indicator is selected based on:
a) Color only
b) Its redox potential relative to the analyte/titrant pair so that a sudden potential shift occurs at equivalence
c) Solubility only
d) Price only
Answer: b - Redox reactions used in titrations should be:
a) Slow and reversible only
b) Rapid and stoichiometric so that endpoint corresponds closely to equivalence
c) Unpredictable and partial
d) Non-stoichiometric
Answer: b - Dichromate (Cr2O7^2−) titrations require which medium?
a) Strongly basic medium only
b) Acidic medium (commonly H2SO4) for dichromate to act as oxidant (Cr2O7^2− + 14H+ + 6e− → 2Cr3+ + 7H2O)
c) Non-aqueous medium only
d) Neutral medium only
Answer: b - Conductometry measures:
a) Voltage between electrodes only
b) Conductance (reciprocal of resistance) of solution and its change during titration etc.
c) Mass of precipitate
d) pH only
Answer: b - The cell constant of a conductivity cell depends on:
a) Electrode material only
b) Geometry of the electrodes and distance between them (cell constant = l/A)
c) Colour of solution
d) Temperature only
Answer: b - Conductometric titrations are particularly useful when:
a) No change in ionic composition occurs
b) There is a significant change in ionic concentration or mobility at equivalence (e.g., precipitation or replacement reactions)
c) Only non-ionic species are present
d) Titration is purely colorimetric
Answer: b - In acid–base conductometric titration of HCl with NaOH the conductance initially:
a) Increases due to replacement of H+ (high mobility) by Na+ (lower mobility) leading to changes and a breakpoint near equivalence
b) Remains constant
c) Decreases uniformly always
d) Jumps to zero immediately
Answer: a - Potentiometry measures:
a) Current under constant voltage only
b) Cell potential (voltage) between indicator and reference electrodes without drawing current (or with negligible current)
c) Mass changes only
d) Conductivity only
Answer: b - A standard hydrogen electrode (SHE) is used as:
a) A common reference electrode with defined potential of 0.00 V under standard conditions
b) An indicator electrode for pH only
c) An obsolete instrument only
d) A precipitation electrode only
Answer: a - A calomel electrode is:
a) An example of a reference electrode (saturated calomel electrode SCE containing Hg/Hg2Cl2) with well-defined potential vs SHE
b) A type of glass electrode
c) Always the same potential as SHE
d) Used to measure conductivity only
Answer: a - The silver/silver chloride electrode (Ag/AgCl) is:
a) A non-reference electrode only
b) A common reference electrode with stable potential in chloride-containing solutions
c) Extremely unstable always
d) Used only for gravimetry
Answer: b - Indicator electrodes include:
a) Metal electrodes (e.g., Pt), gas electrodes, ion-selective electrodes and glass electrode for pH measurement
b) Only platinum wires
c) Colorimetric strips only
d) Plastic rods only
Answer: a - The glass electrode responds to:
a) Sodium ion directly only
b) Hydrogen ion activity (pH) by developing a potential across a special glass membrane
c) Conductivity directly only
d) Redox potential only
Answer: b - In potentiometric titration, the endpoint can be detected by:
a) A sudden change in measured potential vs volume of titrant (often the maximum in derivative plot dE/dV)
b) Smell only
c) Observing precipitation only
d) Color only always
Answer: a - Polarography is an electrochemical technique that records:
a) Current vs applied potential using a dropping mercury electrode or other working electrodes — giving polarogram curves characteristic of reducible species
b) pH vs time only
c) Conductivity vs temperature only
d) Mass vs potential only
Answer: a - The dropping mercury electrode (DME) is widely used in polarography because:
a) Mercury is solid at room temp only
b) It provides a constantly renewing smooth surface and reproducible diffusion conditions for reduction processes
c) It is non-toxic and easy to dispose of always
d) It has no advantages at all
Answer: b - The Ilkovic equation in polarography relates diffusion current (id) to:
a) Concentration of electroactive species, rate of mercury drop formation (drop time), diffusion coefficient and other constants — so Id ∝ n D^1/2 C t^1/6 (form depends on derivation)
b) Solubility only
c) Color of solution only
d) pH only
Answer: a - Rotating platinum electrodes are used for:
a) Static analyses only
b) Increasing mass transport (convection) to the electrode to improve sensitivity and control of limiting current in polarographic-like techniques (RDE = rotating disk electrode)
c) Making solutions hot
d) Making solutions acidic only
Answer: b - In conductometric titrations involving precipitation (e.g., AgNO3 + NaCl), end-point is signalled by:
a) No change in conductance ever
b) A change in slope when chloride is consumed and free Ag+ appears (ionic composition changes)
c) Permanent blue colour
d) Temperature drop only
Answer: b - Ionic mobility order (common ions) shows that H+ has:
a) Lowest mobility of common cations
b) Very high mobility compared with most other cations (hence H+ strongly influences conductance)
c) Same mobility as Na+ always
d) No mobility
Answer: b - Potentiometric titration is advantageous over visual indicators when:
a) Solutions are colored or turbid or indicators interfere — the potentiometric curve gives an objective endpoint detection
b) Visual detection is perfect always
c) Color change is dramatic always
d) pH meters are unavailable
Answer: a - A standardization of reference electrodes is necessary because:
a) Reference electrodes have fixed potential for all conditions always
b) Junction potentials and chloride concentration may alter practical potential so proper maintenance and calibration against standards helps accuracy
c) They never change potential
d) They are disposable only
Answer: b - In polarography, peak or wave heights are proportional to:
a) Concentration of electroactive species (under diffusion-controlled conditions the limiting (diffusion) current is proportional to concentration)
b) Only pH always
c) Shape of beaker only
d) Colour of electrode only
Answer: a - Electrochemical methods are particularly useful for:
a) Trace analysis of electroactive species and monitoring redox active pharmaceuticals and impurities
b) Only bulk weight measurement
c) Non-electroactive analytes only
d) Only color changes
Answer: a - The main safety/environmental concern with dropping mercury electrodes is:
a) Mercury toxicity and disposal — requires strict handling and waste disposal protocols
b) Mercury is completely safe
c) Mercury is never used in labs
d) Mercury is explosive always
Answer: a - The diffusion current in Ilkovic equation increases with:
a) Decreasing concentration
b) Increasing concentration and diffusion coefficient and appropriate mercury drop parameters
c) Lower diffusion coefficient only
d) Solvent colour
Answer: b - In a conductometric titration of a weak acid by a strong base, the conductivity:
a) Always decreases monotonically to zero
b) Initially decreases (replacement of H+ with less mobile Na+) then increases after equivalence (excess OH− contributes to conductance) — giving a minimum at equivalence region
c) Is identical at all points
d) Jumps to infinity at equivalence
Answer: b - The electrode potential of a metal electrode depends on:
a) The concentration/activity of the metal ion in solution and the electrode half-reaction (Nernst equation)
b) Colour of metal only
c) Shape of beaker only
d) Ambient light only
Answer: a - The Nernst equation relates potential to:
a) Temperature, number of electrons transferred, standard potential and activities/concentrations of redox species — useful for predicting electrode potentials
b) Only current and resistance
c) Colour only
d) Density only
Answer: a - In potentiometric titrations, a “blank” titration is useful to account for:
a) Background potential/junction potentials, reagent impurities and baseline corrections before titrating the analyte
b) Colour changes only
c) Indicating nothing
d) Heating effects only
Answer: a - The choice of reference electrode for potentiometry depends on:
a) Compatibility with solution (e.g., chloride concentration for Ag/AgCl electrode) and stability, ease of use and required potential reproducibility
b) Colour of instrument
c) Only cost matters
d) None of the above
Answer: a - Polarographic half-wave potential (E1/2) is characteristic of:
a) A solvent only
b) Each reducible species under given conditions — used for qualitative identification of species
c) Electrode material only
d) Colour of solution only
Answer: b - Limiting diffusion current in polarography is controlled by:
a) Kinetic factors only, not diffusion
b) Rate of mass transport (diffusion + convection), concentration of analyte and geometry of electrode/drop parameters
c) pH only always
d) Presence of indicator only
Answer: b - Conductometric titrations are unsuitable for systems where:
a) Ionic strength changes markedly at equivalence
b) No change in number or type of ions occurs on reaction (no change in conductance) — then no breakpoint observed
c) Precipitation occurs producing significant change in ionic composition
d) Ion mobility is very distinct between reactants and products
Answer: b - Potentiometric pH titrations can detect endpoints more accurately than visual indicators because:
a) pH meter readings are less subjective and can show rapid potential change precisely at equivalence even when colour changes are ambiguous
b) pH meters are always cheap and disposable
c) Visual indicators are always better
d) Potentiometry never drifts
Answer: a - The working electrode in polarography must be:
a) An inert smooth surface (e.g., mercury for DME) to provide reproducible diffusion conditions and well-defined current-potential waves
b) A porous cloth always
c) A solid metal that dissolves rapidly
d) Never inert
Answer: a - Which parameter is NOT part of Ilkovic equation?
a) Concentration of electroactive species
b) Diffusion coefficient
c) Drop time or flow parameter of mercury electrode
d) Colour of solution
Answer: d - In a rotating disk electrode (RDE) experiment, increasing rotation speed:
a) Decreases mass transport to electrode
b) Increases convection, increases limiting current up to controlled regime — used to study kinetics and diffusion
c) Has no effect on current
d) Changes pH drastically always
Answer: b - Endpoints in potentiometric titrations can be located by plotting:
a) Electrode potential vs volume and its first derivative (dE/dV) or second derivative for more precision
b) Colour vs time only
c) Mass vs volume only
d) Temperature vs current only
Answer: a - A reference electrode should ideally have:
a) Unstable and changing potential
b) A stable and well-known potential, low impedance and reproducible junction potential
c) Large size only
d) No particular properties
Answer: b - Common interference in polarography includes:
a) Adsorption of surface-active impurities onto mercury drop changing diffusion conditions and wave shapes
b) Only pH changes, nothing else
c) Light only
d) Buffer color only
Answer: a - The sensitivity of polarography for trace analysis is high mainly because:
a) Electrochemical detection has low detection limits for reducible/oxidizable species when diffusion-limited currents are measured and background current minimized
b) Solutions are always coloured
c) Gravity helps detection
d) Turbidity is key
Answer: a - The potential window of a solvent or electrode system in polarography defines:
a) The pH of the solution only
b) The range of potentials where the solvent and electrode are stable and background currents are manageable for analyte detection
c) The colour of the solvent only
d) The noise level only
Answer: b - A standard addition method in polarography helps to:
a) Remove all impurities permanently
b) Compensate for matrix effects by adding known increments of analyte and extrapolating to zero addition to determine original concentration
c) Increase electrode size only
d) Change electrode geometry only
Answer: b - Which of the following is a typical application of conductometry?
a) Monitoring precipitation reactions, acid–base titrations where ionic composition changes, and determining end-points when visual indicators aren’t suitable
b) Only measuring boiling point
c) Weighing solids only
d) Chromatography only
Answer: a - Which electrode is commonly used as a pH reference in many laboratory potentiometric measurements?
a) Saturated calomel electrode (SCE) or Ag/AgCl electrode depending on system requirements
b) Platinum electrode only
c) Glass rod only
d) Mercury thermometer only
Answer: a - The main limitation of the dropping mercury electrode (DME) is:
a) It is the only electrode with no limits
b) Mercury toxicity and environmental disposal concerns restrict its use — modern labs look for alternatives
c) It never gives reproducible drops
d) It cannot detect any electroactive species
Answer: b - The potential measured by a glass electrode depends on:
a) Activity of H+ ions on both sides of the glass membrane, temperature and ionic strength to some extent (Nernst-type response)
b) Only the concentration of Na+ always
c) Colour of glass only
d) Magnetic field only
Answer: a - In conductometric titration of AgNO3 vs NaCl, the conductance after equivalence increases because:
a) Precipitate dissolves only
b) Excess Ag+ (or other ions) remain in solution with different mobility leading to changed conductance compared to initial chloride-bearing solution
c) Solvent evaporates only
d) Colour change happens only
Answer: b - A good practice before measuring conductivity is to:
a) Not rinse the cell ever
b) Calibrate the cell constant with standard KCl solution and control temperature because conductivity depends strongly on temperature
c) Use unpurified water only
d) Heat the cell to boiling always
Answer: b - In EDTA titrations for Mg2+, the reaction stoichiometry is usually:
a) 1:1 (one mole EDTA complexes one mole metal ion) under appropriate pH and buffering conditions
b) 2:1 always
c) 1:3 always
d) 3:1 always
Answer: a - Potentiometric titration curves for redox titrations show:
a) No change at equivalence
b) Distinct potential jump near equivalence that can be used to determine endpoint precisely
c) Only small noise always
d) Curves identical to pH titrations always
Answer: b - The major advantage of electrochemical titration methods (potentiometric, conductometric, polarographic) in pharmaceutical analysis is:
a) They are always cheaper than volumetry
b) They provide objective and sensitive endpoint detection, work in coloured or turbid solutions, and offer capability for trace analysis of electroactive species
c) They never need calibration
d) They are unaffected by matrix effects always
Answer: b
Hi…! Currently, I am working as an Professor at Department of Pharmaceutical Chemistry(H.O.D),The Pharmaceutical College, Barpali, Odisha. I have more than 19 years of teaching & research experience in the field of Chemistry & Pharmaceutical sciences.