Qualitative Analysis: Principles and Techniques for Identifying Ions and Molecules

Question 1

What color precipitate results when Fe³⁺ ions react with NH₄SCN?

Accepted Answer

Red

Answer

Blue

Answer

Yellow

Answer

Green

Question 2

Which characteristic is associated with cations?

Accepted Answer

Positively charged

Answer

Negatively charged

Answer

Neutral

Answer

Water-repelling

Question 3

For identifying organic molecules, which technique is commonly used?

Accepted Answer

Infrared (IR) spectroscopy

Answer

Flame test

Answer

Titration

Answer

Conductivity measurement

Question 4

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

Accepted Answer

To determine the presence of specific elements.

Answer

To separate ions based on their charge.

Answer

To identify anions in a sample.

Answer

To measure the concentration of a solution.

Question 5

Which of the following reagents is used to precipitate chloride ions in qualitative analysis?

Accepted Answer

Silver nitrate

Answer

Sodium hydroxide

Answer

Potassium iodide

Answer

Barium chloride

Question 6

What is the main goal of qualitative analysis?

Accepted Answer

To identify the presence or absence of specific ions or molecules.

Answer

To determine the exact concentration of a substance.

Answer

To separate and purify chemicals.

Answer

To synthesize new compounds.

Question 7

Which of the following is an example of a redox reaction in qualitative analysis?

Accepted Answer

The reaction of potassium permanganate with oxalic acid

Answer

The reaction of silver nitrate with sodium chloride

Answer

The reaction of hydrochloric acid with sodium hydroxide

Answer

The reaction of copper sulfate with potassium iodide

Question 8

Which of the following is a limitation of qualitative analysis?

Accepted Answer

It cannot provide quantitative information.

Answer

It can only be used to identify a limited number of ions.

Answer

It requires specialized equipment.

Answer

It is time-consuming.

Question 9

What is the role of buffers in qualitative analysis?

Accepted Answer

To maintain a constant pH during reactions.

Answer

To accelerate reactions.

Answer

To prevent precipitation.

Answer

To enhance the solubility of ions.

Question 10

In flame tests, the color of the flame primarily depends on the:

Accepted Answer

Type of element being tested

Answer

Temperature of the flame

Answer

Amount of sample used

Answer

Presence of impurities

Question 11

Which of the following techniques is commonly used to separate cations based on their solubility differences?

Accepted Answer

Precipitation

Answer

Filtration

Answer

Extraction

Answer

Chromatography

Question 12

The formation of a white precipitate upon the addition of BaCl2 solution to an unknown solution suggests the presence of which ion?

Accepted Answer

SO42-

Answer

Ca2+

Answer

Mg2+

Answer

Cl-

Question 13

In a neutralization reaction, which of the following is a characteristic observation?

Accepted Answer

Change in pH

Answer

Formation of a gas

Answer

Increase in temperature

Answer

Precipitation

Question 14

The process of removing impurities from a substance is known as:

Accepted Answer

Purification

Answer

Extraction

Answer

Titration

Answer

Chromatography

Question 15

The separation of components based on their different interactions with a stationary and mobile phase is a characteristic of:

Accepted Answer

Chromatography

Answer

Spectroscopy

Answer

Titration

Answer

Gravimetric analysis

Question 16

Which of the following is NOT typically used as a precipitation reagent in qualitative analysis?

Accepted Answer

Potassium permanganate

Answer

Ammonium hydroxide

Answer

Sodium hydroxide

Answer

Barium chloride

Question 17

What is the primary role of a buffer solution in qualitative analysis?

Accepted Answer

To maintain a constant pH during reactions

Answer

To increase the solubility of precipitates

Answer

To prevent the formation of unwanted precipitates

Answer

To improve the sensitivity of analytical methods

Question 18

What is the principle behind gravimetric analysis?

Accepted Answer

Measuring the weight of a precipitate to determine the concentration of an ion

Answer

Using a flame test to identify specific elements

Answer

Separating ions based on their solubilities

Answer

Determining the pH of a solution using a pH meter

Question 19

Which of the following is a qualitative analysis technique that utilizes the absorption or emission of light?

Accepted Answer

Spectroscopy

Answer

Precipitation

Answer

Titration

Answer

Chromatography

Question 20

Identify the characteristic of a desirable qualitative analysis method:

Accepted Answer

High selectivity

Answer

Low sensitivity

Answer

Fast and inexpensive

Answer

Requires specialized equipment

Question 21

Explain the difference between a cation and an anion:

Accepted Answer

Cations are positively charged ions, while anions are negatively charged ions

Answer

Cations are negatively charged ions, while anions are positively charged ions

Answer

Cations are neutral ions, while anions are charged ions

Answer

Anions are neutral ions, while cations are charged ions

Question 22

A flame test is specifically used to determine the presence of which element in a sample?

Accepted Answer

Sodium

Answer

Potassium

Answer

Iron

Answer

Copper

Question 23

Which chemical reaction is commonly used to confirm the presence of chloride ions (Cl-) in a solution?

Accepted Answer

AgNO3 + Cl- -> AgCl (white precipitate)

Answer

FeCl3 + OH- -> Fe(OH)3 (brown precipitate)

Answer

CuSO4 + Cl- -> CuCl2 (blue solution)

Answer

NaOH + Cl- -> NaCl + H2O (no reaction)

Question 24

Which of the following anions can be detected using the BaCl2 test?

Accepted Answer

Sulfate (SO42-)

Answer

Nitrite (NO2-)

Answer

Bromide (Br-)

Answer

Chloride (Cl-)

Question 25

Which of the following factors can significantly impact the accuracy and reliability of qualitative analysis results?

Accepted Answer

Contamination of samples during collection or handling

Answer

Time of day the analysis is performed

Answer

Lighting conditions in the laboratory

Answer

Temperature variations within the laboratory

Question 26

What is the primary purpose of using a spotting plate in qualitative analysis?

Accepted Answer

To hold and manipulate small drops of solutions for testing purposes.

Answer

To separate different ions in a solution based on their solubility.

Answer

To neutralize acidic or basic samples before analysis.

Question 27

What is a key advantage of using qualitative analysis in chemistry?

Accepted Answer

Provides preliminary information on the composition of samples, guiding further analysis.

Answer

Can be used to synthesize new compounds with desired properties.

Answer

Gives precise quantitative measurements of specific ions in a sample.