Manometer - Example 1

Example 1:

Figure above shows a manometer containing mercury connected to a tank with methane liquid and gas. Find the pressure of the gas supply in the units cmHg and Pa.
[Density of mercury = 13.6 x 10³ kg/m³; atmospheric pressure = 76 cmHg]

Answer:
Pressure of the gas in cmHg

P = 20 + 76 = 96 cmHg

Pressure of gas in Pa
The atmospheric pressure,
$$P_{atm}=(0.76)(13.6\times {10}^3)(10)=103,360Pa$$ Pressure of the gas,
$$\begin{array}{l}P=h\rho g+P_{atm}\\ P=(0.2)(13.6\times {10}^3)(10)+103,360=130,560Pa\end{array}$$