A researcher dispenses distilled deionized water from a 20-ml volumetric pipet into an empty 8.4376 g weighting bottle. If the total mass of water and weighting bottle is 28.5845 g, what is the volume of the water delivered by the 20-ml pipet? The density of water is 0.9967867 g/ml.

As given that some volume of water has been dispensed say "x mL"

The initial weight of bottle = 8.4376 g

The final weight of bottle + water = 28.5845 g

So weight of water transferred = 28.5845 g - 8.4376 g = 20.1469 g

Now there is a relation between density, mass and volume

density = mass / volume

Therefore

Volume = mass / density

So volume of water dispensed = mass dispensed / density = 20.1469 g / 0.9967867 g/ml.

Volume of water = 20.2118467 mL