Question

On a cool, rainy day, the barometric pressure is 698 mmHg. Calculate the barometric pressure in centimeters of water (cmH2O). Density of Hg = 13.5 g/mL; d of H2O = 1.00 g/mL.

Answer 1

Answer:

Barometric pressure is 942.3 cm of column of water.

Explanation:

We can measure barometric pressure by measuring the height h of a column of fluid (this column of fluid exerts the same pressure as the column of air of which we are measuring pressure) using the following formula:

$P = \rho*g*h$

Where ρ is the density of the fluid used and g the acceleration of gravity.

Knowing that both the column of mercury (to match units, we know that 698 mmHg are the same as 69.8 cmHg) and the column of water are representing the same pressure, we can match expressions and find h for the column of water:

$\rho_{Hg} *g*h_{Hg} =\rho_{Water} *g*h_{Water}\\ \\h_{Water}=\frac{rho_{Hg} *g*h_{Hg}}{\rho_{Water} *g} = \frac{13.5g/mL *9.8m/s^{2} *69.8cm}{1g/mL *9.8m/s^{2}}=942.3 cmH_{2}O$