Question

A sample of gas is trapped in a manometer and the stopcock is opened. The level of mercury moves to a new height as can be seen in the diagram. If the pressure of the gas inside the manometer is 815 $torr$, what is the atmospheric pressure in this case?

• A. 760 $torr$
• B. 740 $torr$
• C. 750 $torr$
• D. 815 $torr$
• E. 880 $torr$

Answer 1

The correct option is C 750 $torr$

The difference in the mercury level corresponds to a pressure of 65 $torr$.
The pressure of the gas inside the manometer is 815 $torr$. The atmospheric pressure is $815-65=750torr$.