Pressure Question using 'mm-Hg'

[FollowTheFez]

Homework Statement

Intravenous infusions are often made under gravity. Assuming the fluid has a density of 1.00g/cm^3, at what height h should the bottle be placed so the liquid pressure is 55mm-Hg?

Homework Equations

Atmospheric pressure, Po, = 101kPa = 101000Pa
density of fluid, ρ, = 1g/cm^3 = 1000kg/m^3
density of Hg, ρ, = 13.6x10^3

P=ρgh
P=Po + pgh

The Attempt at a Solution

Pressure of Hg, P= ρgh
= (13.6x10^3) x 9.8 x (5.5x10^-3)
= 733.04 Pa

P=Po + pgh

h= \frac{P - Po}{ρg}
h= \frac{733.04 - 101000}{1000 x 9.8}
h= -10.23

Therefore, the bag must be 10.23m below whatever the reference point is. Which is obviously wrong!


The answer gives nearly what I've got but I don't understand one aspect of it.
It says...

h= \frac{ΔP}{ρg}
h= \frac{(55mm-Hg)(\frac{133Pa}{1mm-Hg})}{1000 x 9.8}
h= 0.75m

I don't understand where the 133Pa came from and why they are doing this calculation.
Can someone please explain?

 

[SteamKing]

5.5*10^-3 m is 5.5 mm, not 55 mm.