measuring gas pressure

Question

1.     Measuring Gas Pressure with a Manometer. Oyster shells are composed of calcium carbonate (CaCO3). When the shells are roasted, they produce solid calcium oxide (CaO) and CO2. A chemist roasts some oyster shells in an evacuated flask that is attached to a manometer (Figure 3 below). When the roasting is complete, and the system has cooled to room temperature, the difference in levels of mercury (∆h) in the arms of the manometer is 144 mm (Figure 4 below). Calculate the pressure created by the CO2(g) in (a) torr, (b) atmospheres, and (c) kilopascals on a day when the atmospheric pressure is 758 torr.

Answer 1

(a) Since we don't see the figures (3 and 4) we can't tell which arm is higher so we'll assume that the pressure increased so the new pressure would be 758 torr + 144 torr = 902 torr (note: 1 mm Hg = 1 torr)

(b) 902 torr x 1 atm/760 torr = 1.19 atm

(c) 1.19 atm x 101.325 kPa/atm = 121 kPa