Final answer:
The density of kerosene is calculated using the hydrostatic pressures of water and mercury in a U-tube. By equating the pressures and using known densities of water and mercury, kerosene's density is determined to be 0.8 g/cm³.
Step-by-step explanation:
To calculate the density of kerosene given the columns of water and mercury in a U-tube, we need to apply the principles of hydrostatic pressure. At equilibrium, the pressure at the base of both columns is the same. Since density is defined as mass divided by volume, we use the given heights of water (20 cm) and mercury (8 cm) to set up a ratio using their known densities (water = 1.0 g/cm³, mercury = 13.5939 g/cm³).
Let ρ be the density of kerosene. Using the hydrostatic balance, ρ * 20 cm = 13.5939 g/cm³ * 8 cm. Solving for ρ gives us ρ = (13.5939 g/cm³ * 8 cm) / 20 cm = 5.43756 g/cm³ / 20 cm = 0.8 g/cm³. Therefore, the correct choice is B. 0.8 g/cm³.