Sampling and Sample Preparation

Description: This quiz covers the fundamental concepts and techniques of sampling and sample preparation in chemistry.
Number of Questions: 15
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Tags: sampling sample preparation chemistry
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What is the primary purpose of sampling in chemistry?

  1. To obtain a representative portion of a larger population

  2. To determine the exact composition of a substance

  3. To identify the presence of specific compounds

  4. To measure the physical properties of a material


Correct Option: A
Explanation:

Sampling aims to select a small subset of a larger population that accurately reflects the characteristics and composition of the entire population.

Which of the following is a common method for collecting solid samples?

  1. Grab sampling

  2. Composite sampling

  3. Systematic sampling

  4. Stratified sampling


Correct Option: A
Explanation:

Grab sampling involves collecting a single sample from a specific location or time point.

What is the purpose of homogenizing a sample before analysis?

  1. To ensure uniform distribution of components

  2. To reduce the sample size

  3. To remove impurities

  4. To increase the sample's solubility


Correct Option: A
Explanation:

Homogenization ensures that the sample is uniform in composition and that any sub-samples taken will be representative of the entire sample.

Which of the following techniques is commonly used to separate solid particles based on their size?

  1. Filtration

  2. Centrifugation

  3. Distillation

  4. Chromatography


Correct Option: A
Explanation:

Filtration is a physical separation technique that separates solid particles from a fluid by passing the mixture through a filter.

What is the principle behind solvent extraction in sample preparation?

  1. Selective dissolution of compounds based on their solubility

  2. Removal of impurities by precipitation

  3. Separation of compounds based on their boiling points

  4. Conversion of compounds into their derivatives


Correct Option: A
Explanation:

Solvent extraction involves the selective transfer of compounds from one phase to another based on their solubility in different solvents.

Which of the following is a common method for drying solid samples?

  1. Air drying

  2. Freeze drying

  3. Oven drying

  4. Vacuum drying


Correct Option: C
Explanation:

Oven drying is a widely used method for removing moisture from solid samples by heating them in an oven at a controlled temperature.

What is the purpose of acid digestion in sample preparation?

  1. To dissolve metal ions from solid samples

  2. To remove organic matter from samples

  3. To convert compounds into their derivatives

  4. To extract analytes from complex matrices


Correct Option: A
Explanation:

Acid digestion is a technique used to dissolve metal ions from solid samples by treating them with strong acids, often in combination with heat.

Which of the following is a common method for preparing liquid samples for analysis?

  1. Filtration

  2. Centrifugation

  3. Distillation

  4. Evaporation


Correct Option: A
Explanation:

Filtration is often used to remove solid particles or impurities from liquid samples before analysis.

What is the purpose of derivatization in sample preparation?

  1. To improve the volatility of compounds

  2. To increase the solubility of compounds

  3. To enhance the stability of compounds

  4. To convert compounds into their derivatives


Correct Option: D
Explanation:

Derivatization involves chemically modifying compounds to convert them into derivatives that possess desirable properties for analysis.

Which of the following is a common method for extracting analytes from solid samples?

  1. Solid-liquid extraction

  2. Solid-phase extraction

  3. Supercritical fluid extraction

  4. Microwave-assisted extraction


Correct Option: A
Explanation:

Solid-liquid extraction involves contacting a solid sample with a suitable solvent to dissolve and extract the analytes of interest.

What is the purpose of matrix matching in sample preparation?

  1. To minimize matrix effects in analysis

  2. To improve the accuracy of calibration standards

  3. To enhance the sensitivity of analytical methods

  4. To reduce the sample preparation time


Correct Option: A
Explanation:

Matrix matching involves preparing calibration standards and samples in a matrix that is similar to the sample matrix to minimize the effects of matrix components on the analytical results.

Which of the following is a common method for concentrating analytes in liquid samples?

  1. Evaporation

  2. Distillation

  3. Solid-phase extraction

  4. Liquid-liquid extraction


Correct Option: A
Explanation:

Evaporation involves removing the solvent from a liquid sample to concentrate the analytes.

What is the purpose of internal standards in quantitative analysis?

  1. To correct for variations in sample preparation

  2. To calibrate the analytical instrument

  3. To quantify the analytes in the sample

  4. To identify the analytes in the sample


Correct Option: A
Explanation:

Internal standards are added to samples before analysis to correct for variations in sample preparation and instrument performance.

Which of the following is a common method for purifying solid samples?

  1. Recrystallization

  2. Chromatography

  3. Distillation

  4. Extraction


Correct Option: A
Explanation:

Recrystallization involves dissolving a solid sample in a suitable solvent, filtering the solution to remove impurities, and then crystallizing the purified compound from the solution.

What is the purpose of quality control (QC) samples in analytical chemistry?

  1. To assess the accuracy and precision of analytical methods

  2. To calibrate the analytical instrument

  3. To identify the analytes in the sample

  4. To quantify the analytes in the sample


Correct Option: A
Explanation:

QC samples are used to assess the accuracy and precision of analytical methods by analyzing samples with known concentrations of analytes.

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