Master Qualitative Analysis: Identify Substances with Confidence

Question 1

In qualitative analysis, which technique employs an electric field to separate ions in a solution based on their varying migration rates?

Accepted Answer

Electrophoresis

Answer

Flame test

Answer

Precipitation reaction

Answer

Chromatography

Question 2

In qualitative analysis, how can you identify the presence of a halide ion (like chloride, bromide, or iodide) in a solution?

Accepted Answer

A white precipitate forms when silver nitrate solution is added.

Answer

A blue solution forms when copper sulfate solution is added.

Answer

A yellow precipitate forms when potassium iodide solution is added.

Question 3

What is a key limitation of qualitative analysis techniques?

Accepted Answer

They can only tell you if a substance is present or absent, not how much.

Answer

They are not sensitive enough to detect small amounts of substances.

Answer

They cannot distinguish between different substances.

Answer

They are not reliable and give inconsistent results.

Question 4

Which of the following flame tests would produce a yellow-orange flame, indicating the presence of sodium ions?

Accepted Answer

Sodium chloride

Answer

Copper wire

Answer

Lithium chloride

Answer

Potassium chloride

Question 5

In a precipitation reaction, which of the following ions would NOT react with barium ions to form a precipitate?

Accepted Answer

Chloride ions

Answer

Carbonate ions

Answer

Phosphate ions

Answer

Sulfate ions

Question 6

What is the purpose of adding sodium thiosulfate to a solution containing iodine before performing a titration with potassium permanganate?

Accepted Answer

To prevent the formation of elemental iodine

Answer

To act as an indicator

Answer

To increase the reaction rate

Answer

To neutralize the potassium permanganate solution

Question 7

What is the principle behind the separation of ions using ion exchange chromatography?

Accepted Answer

Differences in charge

Answer

Differences in solubility

Answer

Differences in polarity

Answer

Differences in boiling point

Question 8

In a gravimetric analysis, what is the purpose of washing the precipitate before drying and weighing it?

Accepted Answer

To remove impurities

Answer

To increase its weight

Answer

To dissolve the precipitate

Answer

To change its color

Question 9

Which of the following is considered a macroelement in biological samples?

Accepted Answer

Calcium

Answer

Copper

Answer

Iron

Answer

Zinc

Question 10

Which of the following is NOT a widely used method in qualitative analysis?

Accepted Answer

Mass spectrometry

Answer

Flame tests

Answer

Precipitation reactions

Answer

Chromatography

Question 11

A deep blue flame in a flame test indicates the presence of which element?

Accepted Answer

Potassium

Answer

Sodium

Answer

Calcium

Answer

Copper

Question 12

What is the primary purpose of the mobile phase in chromatography?

Accepted Answer

To carry the sample through the stationary phase

Answer

To dissolve the sample

Answer

To separate different components of the sample

Answer

To detect the separated components

Question 13

What is the characteristic color of a positive Molisch's test for carbohydrates?

Accepted Answer

Red-brown

Answer

Yellow

Answer

Blue

Answer

Green

Question 14

What is the principle behind the separation of compounds in size-exclusion chromatography?

Accepted Answer

Differential molecular size

Answer

Differential solubility

Answer

Differential charge interaction

Answer

Differential polarity

Question 15

A solution turns milky when AgNO3 is added. Which of the following ions is most likely present in the solution?

Accepted Answer

SO42-

Answer

Cl-

Answer

CO32-

Answer

NO3-

Question 16

Which analytical technique utilizes the specific colors produced by cations when heated in a flame to aid in their identification?

Accepted Answer

Flame tests

Answer

Precipitation reactions

Answer

Chromatography

Answer

Titration

Question 17

What type of chemical reaction results in the formation of an insoluble solid (precipitate) when two solutions are combined?

Accepted Answer

Precipitation reaction

Answer

Neutralization reaction

Answer

Redox reaction

Answer

Gas evolution reaction

Question 18

Which chromatography technique separates substances based on their electrical charge?

Accepted Answer

Ion exchange chromatography

Answer

Paper chromatography

Answer

Thin-layer chromatography

Answer

Gas chromatography

Question 19

Which cation exhibits a characteristic yellow flame color in a flame test?

Accepted Answer

Sodium

Answer

Potassium

Answer

Calcium

Answer

Copper

Question 20

What is the main purpose of adding a buffer solution in precipitation reactions?

Accepted Answer

To control the pH of the solution

Answer

To increase the concentration of ions in the solution

Answer

To prevent the formation of unwanted precipitates

Answer

To enhance the selectivity of the reaction

Question 21

Qualitative analysis has limitations. Describe scenarios where qualitative analysis methods may not yield reliable results.

Accepted Answer

Analyte concentration is extremely low

Accepted Answer

Sample matrix is highly complex

Accepted Answer

Interfering ions are present

Answer

Analyte concentration is extremely high

Question 22

Which type of chromatography is used to separate substances based on their **polarity**?

Accepted Answer

Thin-layer chromatography

Answer

Ion exchange chromatography

Answer

Gas chromatography

Answer

Size exclusion chromatography

Question 23

The use of a reference solution in qualitative analysis serves to **compare the results of the unknown sample**.

Accepted Answer

Compare the results of the unknown sample

Answer

Calibrate the analytical instrument

Answer

Mask the presence of interfering ions

Answer

Enhance the sensitivity of the analysis

Question 24

Which of the following techniques is NOT used in qualitative analysis?

Accepted Answer

Titrations

Answer

Flame tests

Answer

Precipitation reactions

Answer

Chromatography

Question 25

What is the primary purpose of a flame test in qualitative analysis?

Accepted Answer

To determine the identity of an unknown metal ion

Answer

To measure the concentration of an analyte

Answer

To separate different components of a mixture

Answer

To detect the presence of a specific gas

Question 26

Which of the following precipitation reactions would produce a white precipitate?

Accepted Answer

BaCl₂ + Na₂SO₄

Answer

AgNO₃ + NaCl

Answer

CuSO₄ + NaOH

Answer

FeCl₃ + NH₄OH

Question 27

What is the role of a chelating agent in qualitative analysis?

Accepted Answer

To enhance the color intensity of metal complexes

Answer

To prevent the formation of precipitates

Answer

To adjust the pH of the solution

Answer

To act as a reducing agent

Question 28

Which factor primarily affects the separation of compounds in chromatography?

Accepted Answer

Polarity

Answer

Molecular weight

Answer

Boiling point

Answer

Acidity

Question 29

How can atomic absorption spectroscopy be used to determine the concentration of an analyte?

Accepted Answer

By measuring the amount of light absorbed by the analyte

Answer

By comparing the wavelength of the absorbed light to a standard

Answer

By counting the number of absorbed photons

Answer

By analyzing the emission spectrum of the analyte

Question 30

What is the key difference between qualitative and quantitative analysis?

Accepted Answer

Qualitative analysis identifies the presence of analytes, while quantitative analysis measures their concentrations.

Answer

Quantitative analysis is more precise than qualitative analysis.

Answer

Qualitative analysis is used for research purposes, while quantitative analysis is used for routine testing.

Answer

There is no difference between qualitative and quantitative analysis.

Question 31

In qualitative analysis, we employ specific techniques to detect the presence of substances in a sample. Which of the following is NOT a technique commonly used in this field?

Accepted Answer

Titration

Answer

Flame tests

Answer

Chromatography

Question 32

Which technique is used to distinguish between barium and strontium ions based on their flame colors?

Accepted Answer

Flame test

Answer

Spectroscopy

Answer

Chromatography

Answer

Precipitation reaction with sulfate ions

Question 33

When a solution containing iron(II) ions reacts with sodium hydroxide solution, what is the formula of the white precipitate formed?

Accepted Answer

Fe(OH)2

Answer

Fe3O4

Answer

Fe2O3

Answer

Fe(OH)3

Question 34

Which reagent is commonly used to confirm the presence of chloride ions in a solution?

Accepted Answer

Silver nitrate solution

Answer

Barium chloride solution

Answer

Sodium hydroxide solution

Answer

Potassium iodide solution

Question 35

Which reaction is used specifically to detect bromide ions in a solution?

Accepted Answer

Reaction with chlorine water followed by extraction with organic solvent

Answer

Reaction with silver nitrate solution resulting in precipitation

Answer

Reaction with potassium permanganate solution resulting in oxidation

Question 36

Which of the following techniques is NOT used in qualitative analysis?

Accepted Answer

Atomic absorption spectroscopy

Answer

Precipitation reaction

Answer

Flame test

Answer

Chromatography

Question 37

In a flame test, what does the color of the flame indicate?

Accepted Answer

The element present in the sample

Answer

The concentration of the sample

Answer

The type of fuel used

Answer

The temperature of the flame

Question 38

Which of the following is the correct definition of a precipitate?

Accepted Answer

A solid compound that forms when two solutions are mixed

Answer

A gas that is formed when two substances react

Answer

A solution that contains a dissolved solid

Question 39

What is the primary purpose of chromatography?

Accepted Answer

To separate components of a mixture based on their different properties

Answer

To identify the elements present in a sample

Answer

To measure the concentration of a substance in a sample

Question 40

What component of a chromatography system remains stationary during the separation process?

Accepted Answer

Stationary phase

Answer

Mobile phase

Answer

Sample

Question 41

The selectivity of a chromatography method refers to its ability to:

Accepted Answer

Separate different components of a mixture

Answer

Detect small amounts of a substance

Answer

Quantify the concentration of a substance

Answer

Identify the structure of a compound

Question 42

In qualitative analysis, what is crucial to ensure accurate results?

Accepted Answer

Using appropriate controls and standards

Answer

Using the most expensive equipment available

Answer

Analyzing samples as quickly as possible to avoid contamination

Question 43

Which of the following is NOT a potential source of error in qualitative analysis?

Accepted Answer

Using clean glassware

Answer

Improperly calibrated equipment

Answer

Contaminated samples

Question 44

When a sodium ion (Na+) is introduced into a flame test, what color does the flame turn?

Accepted Answer

Yellow

Answer

Red

Answer

Green

Answer

Blue

Question 45

Which of these reagents, when added to a solution containing silver ions (Ag+), will produce a white precipitate?

Accepted Answer

Hydrochloric acid (HCl)

Answer

Ammonium hydroxide (NH4OH)

Answer

Sodium hydroxide (NaOH)

Answer

Potassium iodide (KI)

Question 46

Which chromatography technique is primarily used to separate compounds based on their differences in polarity?

Accepted Answer

Thin-layer chromatography (TLC)

Answer

Gas chromatography (GC)

Answer

Gel electrophoresis

Answer

Ion-exchange chromatography

Question 47

An unknown compound reacts with silver nitrate (AgNO3) to form a precipitate but does not react with barium chloride (BaCl2). Which ion is most likely present in the unknown compound?

Accepted Answer

Chloride (Cl-)

Answer

Carbonate (CO32-)

Answer

Sulfate (SO42-)

Answer

Phosphate (PO43-)

Question 48

A blue flame in a flame test strongly suggests the presence of which element in the sample?

Accepted Answer

Potassium

Answer

Calcium

Answer

Sodium

Question 49

Which chromatography technique is most suitable for separating a mixture of dyes based on their distinct colors?

Accepted Answer

Paper chromatography

Answer

Gas chromatography

Answer

Ion-exchange chromatography

Answer

Gel electrophoresis

Question 50

A positive result in the biuret test indicates the presence of which functional group in the compound?

Accepted Answer

Peptide bond

Answer

Carboxyl group

Answer

Carbonyl group

Answer

Amino group

Question 51

What is an essential safety guideline when handling chemicals in the laboratory?

Accepted Answer

Always consult the Material Safety Data Sheet (MSDS) before using a chemical.

Answer

It is acceptable to mix chemicals without knowing their compatibility.

Answer

Never wear gloves when handling chemicals.