Final answer:
The density of mercury, given a mass of 234 g and a volume of 30 cm³, is calculated to be 7.8 g/cm³, which is option A.
Step-by-step explanation:
To calculate the density of mercury, we use the formula density = mass/volume. Given a mass of 234 g and a volume of 30 cm³, we perform the division:
density = 234 g / 30 cm³ = 7.8 g/cm³
The correct answer from the given options is A. 7.8 g/cm³. This value is consistent with the known properties of mercury, which has a high density due to its heavy atomic mass.