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Question
A 1.000 mL sample of acetone, a common solvent used as a paint remover, was placed in a small bottle whose mass was known to be 38.0015 g.
The following values were obtained when the acetone-filled bottle was weighed: 38.7798 g, 38.7795 g and 38.7801 g. How would you characterise the precision and accuracy of these measurements if the actual mass of the acetone was 0.7791 g?
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Solution
Given:
Mass of bottle = 38.0015 g
Actual mass of acetone = 0.7791 g
| Bottle + Acetone | Mass of acetone | Average |
| 38.7798 g | 0.7783 |
= `(0.7783 + 0.7730 + 0.7786)/3` = 0.7780 |
| 38.7795 g | 0.7780 | |
| 38.7801 g | 0.7786 |
Precision = `("highest value" - "lowest value" xx 100)/"lowest value"`
= `(0.7786 - 0.7780)/0.7780 xx 100`
= 0.0007712 × 100
= 0.07712 %
% Accuracy = `("True value" - "observed value")/"True value" xx 100`
= `(0.7791 - 0.7783)/0.7791 xx 100`
= 0.10268
= 0.1027 %
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