# If a manometer reads #"681.7 torr"#, and the mercury is higher on the left half of the sidearm (where the right side is open to the atmosphere) by #"9.96 cm"#, what is the pressure of the gas inside in #"bars"#?

##### 1 Answer

The idea is that the pressure of the gas in the bulb balances out the pressure of the air (the atmospheric pressure) to some extent.

It is implied that *mercury* is in the manometer, and the height **how many**

Since the manometer reads

#Deltah = "9.96 cm Hg" = "99.6 mm Hg" = "99.6 torr"# ,

it means that there is a difference in pressure of *some* direction (less/greater than). To figure out which direction...

Since the mercury is **higher** on the **left** half of the sidearm, it means the pressure of the gas inside is **weaker** than the atmospheric pressure.

Therefore,

#color(green)(P_"gas") = "681.7 torr" - "99.6 torr" = color(green)("582.1 torr")#

In

#color(blue)(P_"gas") = 582.1 cancel"torr" xx cancel"1 atm"/(760 cancel"torr") xx (1.01325xx10^5 cancel"Pa")/cancel"1 atm" xx "1 bar"/(10^5 cancel"Pa")#

#=# #color(blue)("0.776 bars")#

*CHALLENGE: What would the pressure of the gas inside be in* *if the mercury level was higher on the right half of the sidearm, with the same*

Answer:

(highlight to see)