It tells us that lithium has a density of 0.5 g/cm³, and asks us what the mass would be with a volume of 20 cm³.
To calculate the mass, we apply the following formula:
m = d · v
We substitute the exercise data in the given formula:
m = (0,5 g/cm³)·(20 cm³)
m = 10 g
With a sample of 20 cm³, its mass would be 10 grams. Alternative "B".
Skandar