A scientist uses an uncalibrated pH meter and measures the pH of a rainwater sample four times. A different pH meter was calibrated using several solutions with known pH. The true pH of the rain was found by the calibrated pH meter to be 5.12. What can be said about the level of accuracy and precision of the uncalibrated pH meter? (LO 1.14)(a) The uncalibrated pH meter is accurate and precise. (b) The uncalibrated pH meter is neither accurate nor precise. (c) The uncalibrated pH meter is accurate but not precise. (d) The uncalibrated pH meter is precise but not accurate.

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insert step 1> Understand the concepts of accuracy and precision. Accuracy refers to how close a measurement is to the true value, while precision refers to how close repeated measurements are to each other.

insert step 2> Review the measurements taken by the uncalibrated pH meter. If the measurements are close to 5.12, the meter is accurate. If the measurements are close to each other, the meter is precise.

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insert step 3> Compare the uncalibrated pH meter's measurements to the true pH value of 5.12. Determine if the measurements are close to this value to assess accuracy.

insert step 4> Examine the consistency of the uncalibrated pH meter's measurements. If the measurements are similar to each other, the meter is precise.

insert step 5> Based on the analysis of accuracy and precision, choose the correct option from the given choices (a, b, c, or d).

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Key Concepts

Accuracy

Accuracy refers to how close a measured value is to the true or accepted value. In this context, the true pH of the rainwater is known to be 5.12, so an accurate measurement would be one that is close to this value. If the uncalibrated pH meter consistently gives readings that differ significantly from 5.12, it would be considered inaccurate.

Precision

Precision indicates the consistency or repeatability of measurements, regardless of their accuracy. If the uncalibrated pH meter provides similar readings across multiple measurements, it is considered precise. However, if those readings are widely spread out or vary significantly, the meter lacks precision, even if some readings might coincidentally be close to the true value.

Calibration

Calibration is the process of adjusting an instrument to ensure its measurements are accurate. A calibrated pH meter uses known pH solutions to set its scale, allowing it to provide reliable readings. In contrast, an uncalibrated pH meter may yield results that are systematically off from the true value, affecting both its accuracy and precision.

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Aerogels are transparent, low-density materials that are nearly 99.8% empty space and excellent insulators against hot and cold. The density of a silica-based aerogel is 3.0 mg/cm3. What is the density in units of g/m3? (LO 1.17) (a) 3.0 * 10-3 g/m3(b) 3.0 * 101 g/m3 (c) 3.0 g/m3(d) 3.0 * 103 g/m3

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Verified step by step guidance

1. insert step 1> Understand the concepts of accuracy and precision. Accuracy refers to how close a measurement is to the true value, while precision refers to how close repeated measurements are to each other.
2. insert step 2> Review the measurements taken by the uncalibrated pH meter. If the measurements are close to 5.12, the meter is accurate. If the measurements are close to each other, the meter is precise.
3. insert step 3> Compare the uncalibrated pH meter's measurements to the true pH value of 5.12. Determine if the measurements are close to this value to assess accuracy.
4. insert step 4> Examine the consistency of the uncalibrated pH meter's measurements. If the measurements are similar to each other, the meter is precise.
5. insert step 5> Based on the analysis of accuracy and precision, choose the correct option from the given choices (a, b, c, or d).

Key Concepts

Accuracy

Accuracy refers to how close a measured value is to the true or accepted value. In this context, the true pH of the rainwater is known to be 5.12, so an accurate measurement would be one that is close to this value. If the uncalibrated pH meter consistently gives readings that differ significantly from 5.12, it would be considered inaccurate.

Precision

Precision indicates the consistency or repeatability of measurements, regardless of their accuracy. If the uncalibrated pH meter provides similar readings across multiple measurements, it is considered precise. However, if those readings are widely spread out or vary significantly, the meter lacks precision, even if some readings might coincidentally be close to the true value.

Calibration

Calibration is the process of adjusting an instrument to ensure its measurements are accurate. A calibrated pH meter uses known pH solutions to set its scale, allowing it to provide reliable readings. In contrast, an uncalibrated pH meter may yield results that are systematically off from the true value, affecting both its accuracy and precision.