The mass of a 50-mL volumetric flask is 40.638 g. After adding 15.0 mL of 95% ethanol and adding enough water to complete the volume to 50.00 mL, the flask weighed 88.219 g. What is the density of the mixture?

Answer

0.9516 grams / mL (50.00 has 4 sig digs.)

Remark

You have a couple of extraneous numbers there. You don't care about anything except the mass of the flask + water/alcohol mixture (88.219 grams). and the mass of the flask (40.638 grams)

Formulas

mass water/alcohol mixture = mass of the flask with fluid - mass flask density = mass / volume

Solution

mass water/alcohol mixture = 88.219 - 40.638 = 47.581

Volume = 50 mL Density = mass / Volume Density = 47.581/50 Density = 0.95162 There are 4 sig digs so the answer should be 0.9516