Video Transcript
The diagram shows a liquid column
manometer connected at one end to a gas reservoir and at the opposite end to the
atmosphere. Which of the following correctly
relates the pressure of the gas and the pressure of the atmosphere, π gas and π
atmosphere? (A) π gas equals π
atmosphere. (B) π gas is less than π
atmosphere. (C) π gas is greater than π
atmosphere.
We need to recall that a manometer
is a U-shaped tube filled with a liquid that is used to measure the pressure of a
gas. In a manometer, the pressure on one
side, in this case, the pressure of the atmosphere, pushes down on the liquid on one
end of the tube. And the pressure on the other end
of the tube, in this case, the pressure from the gas reservoir, pushes down on the
liquid on the other end. The relative pressure of the gases
will determine what height the liquid will go to on either end of the tube.
We can see in our diagram that we
have a difference in height between the liquid on one end of the tube to the liquid
on the other end of the tube. In this case, the height of the
liquid thatβs in the tube attached to the atmosphere is lower than the height of the
liquid in the tube thatβs attached to the gas reservoir. This implies that the pressure the
atmosphere puts on the liquid provides a greater push than the pressure the gas
reservoir puts on the liquid. Or another way to put it would be
that the pressure of the atmosphere is greater than the pressure of the gas in the
gas reservoir. Therefore, we can say that when we
compare the pressure of the gas in the gas reservoir to the pressure of the
atmosphere that the pressure of the gas is going to be less than the pressure of the
atmosphere or answer choice (B).
