Chapter 1
Q. 1.6
To determine the density of ethyl alcohol, a student pipets a 5.00-mL sample into an empty flask weighing 15.246 g. He weighs the flask with the sample and finds the mass to be 19.171 g. What is the density of the ethyl alcohol?
| ANALYSIS | |
| mass of empty flask (15.246 g) mass of flask + sample (19.171 g) volume of sample (5.00 mL) |
Information given: |
| density of the sample | Asked for: |
STRATEGY
1. Find the mass of the sample by difference.
mass of sample = (mass of flask + sample) – (mass of sample)
2. Recall the formula for density.
density = \frac{mass}{volume}
Step-by-Step
Verified Solution
| 1. mass of sample | mass of sample = (mass of flask + sample) – (mass of flask) = 19.171 g – 15.246 g = 3.925 g |
| 2. density | d = \frac{mass}{V} = \frac{3.925 g}{5.00 mL} = 0.785 g/mL |
END POINT
The density is expressed in 3 significant figures because the volume is measured only to 3 significant figures.