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?

Answer 1

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 %