Gravimetric Analysis Challenge

A sample of impure NaCl weighs 10 g. After recrystallization, the pure NaCl obtained weighs 8 g. What is the purity percentage of the sample?

• 75%

• 70%

• 90%

• 80%

Describe the process of vacuum filtration and its advantages over gravity filtration.

• Vacuum filtration is slower than gravity filtration.

• Gravity filtration is more efficient for separating solids from liquids.

• Vacuum filtration is faster and more efficient than gravity filtration, allowing for quicker separation of solids from liquids.

• Vacuum filtration requires more equipment than gravity filtration.

Explain how to determine the endpoint in a gravimetric analysis experiment.

• The endpoint is determined by the color change of the solution.

• The endpoint is reached when the temperature stabilizes.

• The endpoint is indicated by the volume of titrant used.

• The endpoint is determined when the mass of the precipitate is constant.

If a sample contains 15% impurities and the total mass of the sample is 50 g, what is the mass of the pure substance?

• 50 g

• 35 g

• 12.5 g

• 42.5 g

What is the role of a desiccator in gravimetric analysis?

• To increase the temperature of samples during analysis.

• The role of a desiccator in gravimetric analysis is to keep samples dry and prevent moisture absorption.

• To provide a vacuum environment for chemical reactions.

• To store samples in a liquid medium for better analysis.

Discuss the importance of drying the precipitate before weighing in gravimetric analysis.

• The mass of the precipitate is not affected by moisture content.

• Drying the precipitate is essential to obtain an accurate mass, ensuring reliable results in gravimetric analysis.

• Drying the precipitate is unnecessary and can lead to inaccurate results.

• Weighing the wet precipitate provides a more reliable mass measurement.

What is the significance of using a crucible in gravimetric analysis?

• To provide a controlled environment for chemical reactions.

• The crucible is used to contain the precipitate during heating to constant mass.

• To increase the reaction rate of the precipitate formation.

• To allow for the measurement of gas released during the reaction.

How can the purity of a precipitate be determined after filtration and drying?

• The purity is determined by comparing the mass of the precipitate to the expected theoretical mass.

• The purity is assessed by the color of the precipitate.

• The purity can be determined by the volume of the filtrate collected.

• The purity is indicated by the time taken for the filtration process.

What are the key differences between hot and cold vacuum filtration methods?

• Hot vacuum filtration is faster than cold vacuum filtration.

• Cold vacuum filtration is more effective for volatile substances.

• Hot vacuum filtration requires less equipment than cold vacuum filtration.

• Cold vacuum filtration is preferred for heat-sensitive materials.

Why is it important to use a balance with high precision in gravimetric analysis?

• A high-precision balance ensures accurate mass measurements, which are critical for reliable results.

• High precision balances are only necessary for large sample sizes.

• Using a high-precision balance is optional in gravimetric analysis.

• High precision balances are less sensitive to environmental changes.