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Checking a Meter Between Two Reference Points 4 questions
Checking a Meter Between Two Reference Points
Base your answers on the information provided and your knowledge of chemistry. Use the 2025 Chemistry Reference Tables as needed.
A workshop checks a meter that reports dissolved marker concentration. It must read within 0.25 mg/L of the true value at every concentration used. The workshop first checks low and high standards, then adds a middle standard measured independently.
| Standard | Known concentration (mg/L) | Meter reading (mg/L) |
|---|---|---|
| Low | 4 | 4 |
| Middle | 8 | 9 |
| High | 12 | 12 |
Question 1
Which standard directly shows a reading outside the stated tolerance?
- Low only
- Middle only
- High only
- All three
Question 2
A student approves the meter after testing only the low and high standards. Evaluate the approval with the middle reading.
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The workshop makes a fourth sample by mixing equal volumes of the low and high standards. The dissolved marker is conserved and the liquid volumes add. The meter reads 9 mg/L for the mixed sample.
Question 3
Calculate the true concentration of the mixed sample. Decide whether the new reading meets the tolerance.
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Question 4
The technician proposes that only the independently prepared middle standard was mixed incorrectly. Use the mixed sample to evaluate that explanation.
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