A liquid whose density is twice the density of mercury is used as a barometric liquid. Then one atmospheric pressure equals ______ cm of the liquid pressure. 

Concept:

• Atmospheric Pressure
  • Atmospheric pressure is the pressure at any point on the surface of the earth due to the weight of the column of air above that point.
  • Air is an extremely compressible gas having its weight.
  • The pressure exerted by air due to its weight is called atmospheric pressure on the Earth’s surface.
• The Atmospheric pressure at sea level is 1 atm.
• Atmospheric pressure is commonly measured with a barometer.
• Atmospheric pressure is described by meteorologists as how high the mercury rises.
• The standard (symbol: atm) is a unit of atmospheric pressure.
• A barograph is used for the continuous recording of atmospheric pressure.

Calculation:

Given that, ρ_liquid = 2 ρ_mercury, 1atm = ?

Here, p = ρgh (p = pressure, ρ = density, h = height)

p_liq = p_mercury

(ρgh)_liq ∝ (ρgh)mercury .................. (1 atm = 76 cm of Hg) 
h_liq = Barometric h_mercury / ρ_liquid

As the density of the liquid is  twice the density of mercury is used as a barometric liquid

h_liq = 76 / 2 = 38

From the definition, we can say that 1 atm = 38 cm of liquid pressure.