Answer
The correct answer is:
(a) $20~cm~Hg$
Work Step by Step
$P_{abs} = P_g+P_{atm}$
The absolute pressure of the gas is $20~cm~Hg+76~cm~Hg$.
The gauge pressure is the difference between the absolute pressure and the atmospheric pressure. Therefore, the gauge pressure is $20~cm~Hg$
The correct answer is:
(a) $20~cm~Hg$
