PQ1-FINALS-UE

What is the main reason for using a pH buffer during the preparation of the EDTA solution?

• To maintain the solubility of the metal ion

• To ensure a consistent color change during titration

• To prevent oxidation of the solution

• To increase the solubility of EDTA

• To maintain the stability of EDTA

Answer explanation

DTA's effectiveness as a chelating agent depends on maintaining the correct pH, as the metal ion binding is pH-dependent. A buffer ensures that the pH stays stable.

If the molarity of the EDTA solution was calculated as 0.0098M, which of the following actions is most appropriate?

• Discard the solution and prepare a new one

• Adjust the pH to 7

• Dilute the solution to achieve the desired molarity

• Use the solution as is, since the concentration is close to the target

• Re-standardize the solution at a higher concentration

Answer explanation

Since the calculated concentration (0.0098M) is very close to the desired 0.01M concentration, the solution can still be used without significant error.

Which of the following is a critical factor when preparing an EDTA solution to ensure its accurate concentration?

• Type of glassware used

• Stirring speed during mixing

• pH of the solution

• Volume of water used

• Temperature of the solution

Answer explanation

EDTA’s ability to form stable complexes with metal ions is pH-dependent. Ensuring the correct pH during preparation is critical for accurate standardization.

What is the consequence of using an EDTA solution with too high a concentration during standardization?

• The pH of the solution will decrease

• The titration will take longer to reach the endpoint

• The calculation of metal ion concentration will be inaccurate

• The solution will become turbid

• The indicator will not change color

Answer explanation

The calculation of metal ion concentration will be inaccurate

If the titration shows that it requires 10.5 mL of EDTA to titrate a sample of metal ions, and the molarity of EDTA is 0.01M, what is the number of moles of EDTA used?

• 0.0105 mol

• 0.000105 mol

• 0.105 mol

• 1.05 mol

• 10.5 mol

Answer explanation

Moles of EDTA = Molar Concentration of EDTA x Volume of EDTA in (L)

Which of the following steps is involved in the preparation of a 0.01M EDTA solution?

• Adjusting the volume to the desired level with distilled water

• Using a dilute acid to lower the pH of the solution

• Adding a few drops of hydrochloric acid to acidify the solution

• Heating the solution to ensure complete dissolution of EDTA

• Adding a known amount of NaOH to maintain a basic pH

How does the EDTA molecule bind to a metal ion?

• Through hydrogen bonding

• By electrostatic attraction

• By forming a chelate structure through multiple bonds

• Through van der Waals forces

• By ionic bonding

What is the role of EDTA in complexometric titrations?

• To form stable complexes with metal ions

• To change the color of the solution

• To increase the temperature of the solution

• To precipitate metal ions

• To act as a reducing agent

During the preparation of an EDTA solution, why is it important to use distilled water?

• To avoid contamination from impurities

• To enhance the solubility of EDTA

• To ensure the solution is acidic

• To increase the volume of the solution

• To maintain a constant temperature

Which metal ion is typically used as a primary standard for the standardization of EDTA?

• Iron

• Zinc

• Sodium

• Calcium

• Copper