Answer: The density of the unknown liquid is 0.5 g/mL
Step-by-step explanation:
Density of a substance is defined as the ratio of its mass and volume. The equation used to calculate density of a substance is:

We are given:
Mass of unknown liquid = 6 g
Volume of unknown liquid = 12.0 mL
Putting values in above equation, we get:

Hence, the density of the unknown liquid is 0.5 g/mL