Question

A 1.000 mL sample of acetone, a common solvent sometimes 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 characterize the precision and accuracy of these measurements if the true mass of the acetone was 0.7791 g?

Answer 1

See explanation

Step-by-step explanation:

Precision means the reputability of measurement and accuracy means how close a measurement is to the actual value. To get the measured mass of the acetone we need to substract the mass of the bottle from the measured mass of bottle and acetone.

The mass of the bottle is 38.0015g

⇒The mass of acetone in bottle 1= 0.7783g

⇒Mass of acetone in bottle 2= 0.7780g

⇒Mass of acetone in bottle3= 0.7786g

The measured value is near to each other. ⇒ the measurements are precise.

To check the accuracy we can compare the average value to the actual mass of the acetone.

Average of the acetone measurement is (0.7783+0.7780+0.7786)/3 = 0.7783g

The percentage of difference of the average measurement to the actual mass is = {(actual value-measured value)/actual value}x100%

={(0.7791-0.7783)/0.7791}x100%

=0.10%

So we can see the difference is very small ⇒ the measurement is accurate.