Final answer:
To find the gas pressure in the apparatus, subtract h1 from Pbar and add h2. Given Pbar = 740 mmHg, h1 = 30 mm, and h2 = 40 mm, the pressure of the gas is 750 mmHg.
Step-by-step explanation:
The pressure of the gas inside the apparatus can be determined using the given atmospheric pressure (Pbar) and the heights of the mercury (h1 and h2). In a closed-ended manometer with a difference in mercury levels, the pressure of the gas (Pgas) is the atmospheric pressure minus h1 plus h2 when the gas pressure is higher than the atmospheric pressure, which is the case when the mercury level on the side open to the atmosphere (h1) is lower than the mercury level on the side connected to the gas (h2). Therefore, Pgas = Pbar + h2 - h1.
Plugging in the values we have:
Pgas = 740 mmHg + 40 mm - 30 mm
Pgas = 750 mmHg