Qualitative & Quantitative Analysis

300 Question-and-Answer flashcards covering key concepts, definitions, formulas, examples, and calculations from Module 6: Qualitative & Quantitative Analysis, arranged for comprehensive exam review.

What is the main purpose of qualitative analysis?

To reveal the identity or presence/absence of elements and compounds in a sample.

What is the main purpose of quantitative analysis?

To indicate the amount or proportion of each component in a sample.

Give an example of a USP qualitative identification test.

USP ID tests.

Name four general methods of quantitative analysis.

Gravimetric, Volumetric, Physicochemical, and Special methods.

What sample mass is classified as ultra-micro analysis?

Less than 1.0 mg.

What mass range defines micro analysis?

1.0 mg to 10 mg.

How much sample is used in semimicro/meso analysis?

10 mg to 100 mg.

What mass range defines macro analysis?

100 mg to 1000 mg.

Define a major constituent level.

1 % to 100 % of the analyte.

Define a minor constituent level.

0.01 % (100 ppm) to 1 % of the analyte.

Define a trace constituent level.

11 ppb to 100 ppm.

What is an ultratrace constituent level?

Less than 1 ppb.

What does a proximate assay determine for crude drugs?

The total amount of a class of plant principles (a group of compounds).

What does an ultimate assay determine in crude drugs?

The amount of a single chemical species (specific component).

In chemical drugs, what does a proximate partial assay cover?

Selected or trace compounds only.

In chemical drugs, what does a proximate complete assay cover?

Each constituent present.

Name three broad categories of analysis based on the nature of the method.

Chemical/General, Instrumental, and Special methods.

Give two examples of chemical/general methods of analysis.

Titration and gravimetry.

Give two examples of instrumental methods of analysis.

UV-Vis spectroscopy and IR spectroscopy.

Name two special methods often applied to natural products.

Ash content determination and water content determination.

List the three materials-based types of analysis.

Chemical, Physical, Biological.

What type of physical data might be used in qualitative analysis?

Boiling point, melting point, optical purity, refractive index.

What biological model organism can be used to assay oxytocin potency?

Chicken.

Which animal is commonly used in heparin potency assays?

Sheep.

Name three types of errors in chemical analysis.

Random (intermediate), systematic (determinate), and gross errors.

What do random errors primarily affect?

Precision of measurements.

Systematic errors lead to what analytical problem?

Bias affecting accuracy.

Give three potential sources of systematic errors.

Instrumental, method, and personal errors.

How are gross errors usually characterized?

Occasional, often large mistakes that may create outliers.

Define accuracy in chemical analysis.

The closeness of a measured value to the true or accepted value.

Give the formula for absolute error.

E = |X₁ – X₂|.

Express the formula for relative error (percent error).

ER = |X₁ – X₂| / X₂ × 100 %.

Define precision in chemical analysis.

The reproducibility or closeness of a set of measurements taken the same way.

Name four statistical measures used to report precision.

Average deviation, standard deviation, coefficient of variation, range.

What is the arithmetic mean?

The sum of replicate values divided by their number.

Why is the median sometimes preferred over the mean?

It is less affected by extreme values (outliers).

What is titrimetry?

Analysis where the volume of a known reagent consumed indicates the amount of analyte.

What is another term for a titrant?

Volumetric solution or standard solution.

Define titrand.

The analyte or active constituent being analyzed.

What is an indicator in titration?

A compound that changes color near the end point.

What is the equivalence point?

The theoretical point where stoichiometric amounts of titrant and analyte have reacted.

What is meant by the end point in titration?

The experimentally observed point where a physical change shows equivalence has been reached.

State the normality formula relating titrant and analyte at equivalence.

N₁V₁ = N₂V₂.

What is standardization?

Determining the exact concentration of a solution.

What is a primary standard?

A highly pure substance used directly to determine concentration of titrants.

Give two key properties of an ideal primary standard.

High purity and atmospheric stability.

Why is a large molecular weight advantageous in a primary standard?

It minimizes relative weighing error.

What is a secondary standard?

A standard solution standardized by comparison with a primary standard.

Provide the equation for normality using mass and equivalent weight.

N = weight / (equivalent weight × L solution).

What is the equivalent factor for H₂SO₄?

2.

State the equivalent factor for HCl.

1.

What is the equivalent factor for NaOH?

1.

Give the equivalent factor for Al(OH)₃.

3.

How many electrons are gained per permanganate ion (MnO₄⁻ → Mn²⁺)?

5 electrons.

What is the equivalent factor for dichromate (Cr₂O₇²⁻ → 2Cr³⁺)?

6.

In redox titrations, what is the equivalent factor for ferrous ion (Fe²⁺ → Fe³⁺)?

1.

Define direct titration.

A titration using one volumetric solution directly against the analyte.

What is residual titration also called?

Back titration.

During residual titration, why is a second titrant necessary?

To titrate the excess of the first titrant that did not react.

List the four major classes of titrimetric reactions.

Acid-base, oxidation-reduction, complexation, precipitation.

What is acidimetry?

Measurement of a base using a standard acid.

What is alkalimetry?

Measurement of an acid using a standard base.

Name two common aqueous acid-base indicators.

Phenolphthalein and methyl orange/red.

Which indicator is used for strong acid vs. strong base titrations?

Phenolphthalein or methyl orange/red (both suitable depending on pH range).

Which solvent type is used in non-aqueous titrations?

Non-polar solvents.

Name a non-aqueous acidimetry indicator.

Crystal violet.

Name a non-aqueous alkalimetry indicator.

Thymolphthalein.

What is the usual titrant for aqueous alkalimetry?

Sodium hydroxide (NaOH).

Name a primary standard for standardizing NaOH.

Potassium biphthalate (KHP).

What titrant is commonly used for non-aqueous alkalimetry?

Sodium methoxide in ethanol or lithium methoxide in methanol.

Which primary standard is used to standardize sodium methoxide?

Benzoic acid.

What is the self-indicating oxidizing agent in permanganometry?

KMnO₄ (potassium permanganate).

What is the primary standard for KMnO₄ solutions?

Sodium oxalate (Na₂C₂O₄).

What color marks the end point in permanganometry?

A permanent, faint pink color.

Which vitamin is often assayed directly by iodimetry?

Vitamin C (ascorbic acid).

What indicator is used in iodimetric and iodometric titrations?

Starch.

Which titrant is used in iodometry?

Sodium thiosulfate (Na₂S₂O₃).

State the reaction of iodometry involving iodine and thiosulfate.

I₂ + 2 S₂O₃²⁻ → 2 I⁻ + S₄O₆²⁻.

Give an example of a drug assayed by cerimetry.

FeSO₄ tablets or hydroquinone.

What is the indicator ferroin used for?

Detecting the end point in cerimetry (Ce⁴⁺ titrations).

What is the ratio of metal to EDTA in EDTA titrations?

1 : 1.

Which indicator is used for Mg and Zn in EDTA titrations?

Eriochrome Black T (EBT).

Which masking agent selectively masks Fe, Mn, or Al?

Triethanolamine.

Name the three Argentometric methods of precipitation titration.

Volhard, Mohr, and Fajans.

What titrant is used in the Volhard method?

Ammonium thiocyanate (NH₄SCN).

What indicator is used in the Volhard method?

Ferric ammonium sulfate.

What titrant is used in Mohr’s method?

Silver nitrate (AgNO₃).

What is the indicator for Mohr’s method?

Potassium chromate (K₂CrO₄).

Which type of indicator is used in the Fajans method?

Adsorption indicators such as dichlorofluorescein or eosin Y.

Define gravimetry.

Quantitative analysis by isolating and weighing a precipitate of known composition.

What is meant by drying to constant weight in gravimetry?

Two consecutive weighings differ by not more than 0.5 mg per gram of substance.

Give the formula for the gravimetric factor (GF).

GF = MWsample / MWprecipitate (adjusted for stoichiometry).

What is the GF for NaCl when precipitated as AgCl?

GF = MW(NaCl) / MW(AgCl).

In the BaCl₂ + AgNO₃ example, why is the GF multiplied by 2?

Because two moles of AgCl precipitate per mole of BaCl₂.

Define spectroscopy.

The study of the interaction between electromagnetic radiation and matter.

What is a chromophore?

A functional group that absorbs maximum radiation in the UV or visible region.

What is an auxochrome?

A functional group that doesn’t absorb by itself but shifts or intensifies absorption when attached to a chromophore.

List the seven parts/properties of a wave.

Crest, trough, amplitude, wavelength, wavenumber, period, frequency.

Write the wave equation relating speed, wavelength, and frequency.

c = λ ν (speed = wavelength × frequency).

What is Planck’s equation?

E = h ν.