Final answer:
The exact number of droplets created when expelling the last drop from a serological pipet cannot be determined without a specific nominal size, but droplets from common lab pipettes are often in the microliter range.
Step-by-step explanation:
When expelling the "last" drop from a serological pipet, under normal conditions, the number of droplets created with a nominal size is likely very few. Without an explicit nominal size provided in the question, we can refer to common pipette sizes used in laboratories, such as micropipettes ranging from 2 to 200 μm or larger volumetric glass pipettes. Considering the scale of these tools, the droplets would typically be in the microliter range, which is indicated by measurements like 10 μm (micrometers), and an understanding that microliters (μl) are on the scale of 10-6 L (liters). For example, it's well known that a small drop of blood for a blood smear is less than 10 μl, which is a reference that can be related to the likely size of droplets from a pipette.