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Question 1:

What is the purpose of pH calibration?

A) To determine the pH of a solution
B) To adjust the sensitivity of the pH electrode
C) To clean the pH electrode
D) To measure the temperature of the solution

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Explanation: The correct answer is B) To adjust the sensitivity of the pH electrode. pH calibration is performed to adjust the sensitivity of the pH electrode and ensure accurate pH measurements. During calibration, the electrode is immersed in pH buffer solutions with known pH values to calibrate the electrode's response. This allows for precise and reliable pH measurements in subsequent analyses.

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Question 2:

What pH values should be used for two-point calibration of a pH meter?

A) pH 2 and pH 10
B) pH 4 and pH 7
C) pH 7 and pH 10
D) pH 2 and pH 7

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Explanation: The correct answer is B) pH 4 and pH 7. A two-point calibration of a pH meter typically involves using pH 4 and pH 7 buffer solutions. These buffer solutions provide two reference points for calibration, allowing for adjustments to the pH meter's sensitivity and accuracy. The pH meter's calibration curve is created based on these known pH values.

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Question 3:

What is the importance of maintaining pH buffer integrity during calibration?

A) To prevent contamination of the pH electrode
B) To ensure accurate pH measurements
C) To extend the lifespan of the pH electrode
D) To measure the temperature of the solution

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Explanation: The correct answer is B) To ensure accurate pH measurements. Maintaining pH buffer integrity during calibration is crucial to ensure accurate pH measurements. pH buffers are used as reference solutions with known pH values. Any contamination or deviation in the buffer solutions can lead to calibration errors and inaccurate pH readings. Proper storage and handling of the buffers are essential to maintain their integrity.

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Question 4:

What is the purpose of rinsing the pH electrode with distilled water between measurements?

A) To clean the pH electrode
B) To remove any residual buffer solution
C) To prevent cross-contamination of samples
D) To measure the temperature of the solution

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Explanation: The correct answer is C) To prevent cross-contamination of samples. Rinsing the pH electrode with distilled water between measurements is done to prevent cross-contamination of samples. It helps remove any residual buffer solution or sample from the electrode, reducing the risk of carrying over contaminants that could affect subsequent measurements. Distilled water is used as it does not interfere with the pH measurements.

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Question 5:

What is the purpose of zero-point calibration in pH measurement?

A) To adjust the pH electrode's sensitivity
B) To measure the temperature of the solution
C) To calibrate the pH meter's temperature compensation
D) To eliminate electrode offsets and ensure accurate readings

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Explanation: The correct answer is D) To eliminate electrode offsets and ensure accurate readings. Zero-point calibration in pH measurement is performed to eliminate electrode offsets or any systematic errors in the pH measurement system. It involves immersing the electrode in a pH buffer solution with a known pH of 7. The zero-point calibration removes any voltage offsets and ensures accurate readings at pH 7.